x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU...

[cris-mirror.git] / drivers / infiniband / hw / hfi1 / pio.c

/*
 * Copyright(c) 2015-2017 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  - Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <linux/delay.h>
#include "hfi.h"
#include "qp.h"
#include "trace.h"

#define SC_CTXT_PACKET_EGRESS_TIMEOUT 350 /* in chip cycles */

#define SC(name) SEND_CTXT_##name
/*
 * Send Context functions
 */
static void sc_wait_for_packet_egress(struct send_context *sc, int pause);

/*
 * Set the CM reset bit and wait for it to clear.  Use the provided
 * sendctrl register.  This routine has no locking.
 */
void __cm_reset(struct hfi1_devdata *dd, u64 sendctrl)
{
        write_csr(dd, SEND_CTRL, sendctrl | SEND_CTRL_CM_RESET_SMASK);
        while (1) {
                udelay(1);
                sendctrl = read_csr(dd, SEND_CTRL);
                if ((sendctrl & SEND_CTRL_CM_RESET_SMASK) == 0)
                        break;
        }
}

/* defined in header release 48 and higher */
#ifndef SEND_CTRL_UNSUPPORTED_VL_SHIFT
#define SEND_CTRL_UNSUPPORTED_VL_SHIFT 3
#define SEND_CTRL_UNSUPPORTED_VL_MASK 0xffull
#define SEND_CTRL_UNSUPPORTED_VL_SMASK (SEND_CTRL_UNSUPPORTED_VL_MASK \
                << SEND_CTRL_UNSUPPORTED_VL_SHIFT)
#endif

/* global control of PIO send */
void pio_send_control(struct hfi1_devdata *dd, int op)
{
        u64 reg, mask;
        unsigned long flags;
        int write = 1;  /* write sendctrl back */
        int flush = 0;  /* re-read sendctrl to make sure it is flushed */

        spin_lock_irqsave(&dd->sendctrl_lock, flags);

        reg = read_csr(dd, SEND_CTRL);
        switch (op) {
        case PSC_GLOBAL_ENABLE:
                reg |= SEND_CTRL_SEND_ENABLE_SMASK;
        /* Fall through */
        case PSC_DATA_VL_ENABLE:
                /* Disallow sending on VLs not enabled */
                mask = (((~0ull) << num_vls) & SEND_CTRL_UNSUPPORTED_VL_MASK) <<
                                SEND_CTRL_UNSUPPORTED_VL_SHIFT;
                reg = (reg & ~SEND_CTRL_UNSUPPORTED_VL_SMASK) | mask;
                break;
        case PSC_GLOBAL_DISABLE:
                reg &= ~SEND_CTRL_SEND_ENABLE_SMASK;
                break;
        case PSC_GLOBAL_VLARB_ENABLE:
                reg |= SEND_CTRL_VL_ARBITER_ENABLE_SMASK;
                break;
        case PSC_GLOBAL_VLARB_DISABLE:
                reg &= ~SEND_CTRL_VL_ARBITER_ENABLE_SMASK;
                break;
        case PSC_CM_RESET:
                __cm_reset(dd, reg);
                write = 0; /* CSR already written (and flushed) */
                break;
        case PSC_DATA_VL_DISABLE:
                reg |= SEND_CTRL_UNSUPPORTED_VL_SMASK;
                flush = 1;
                break;
        default:
                dd_dev_err(dd, "%s: invalid control %d\n", __func__, op);
                break;
        }

        if (write) {
                write_csr(dd, SEND_CTRL, reg);
                if (flush)
                        (void)read_csr(dd, SEND_CTRL); /* flush write */
        }

        spin_unlock_irqrestore(&dd->sendctrl_lock, flags);
}

/* number of send context memory pools */
#define NUM_SC_POOLS 2

/* Send Context Size (SCS) wildcards */
#define SCS_POOL_0 -1
#define SCS_POOL_1 -2

/* Send Context Count (SCC) wildcards */
#define SCC_PER_VL -1
#define SCC_PER_CPU  -2
#define SCC_PER_KRCVQ  -3

/* Send Context Size (SCS) constants */
#define SCS_ACK_CREDITS  32
#define SCS_VL15_CREDITS 102    /* 3 pkts of 2048B data + 128B header */

#define PIO_THRESHOLD_CEILING 4096

#define PIO_WAIT_BATCH_SIZE 5

/* default send context sizes */
static struct sc_config_sizes sc_config_sizes[SC_MAX] = {
        [SC_KERNEL] = { .size  = SCS_POOL_0,    /* even divide, pool 0 */
                        .count = SCC_PER_VL },  /* one per NUMA */
        [SC_ACK]    = { .size  = SCS_ACK_CREDITS,
                        .count = SCC_PER_KRCVQ },
        [SC_USER]   = { .size  = SCS_POOL_0,    /* even divide, pool 0 */
                        .count = SCC_PER_CPU }, /* one per CPU */
        [SC_VL15]   = { .size  = SCS_VL15_CREDITS,
                        .count = 1 },

};

/* send context memory pool configuration */
struct mem_pool_config {
        int centipercent;       /* % of memory, in 100ths of 1% */
        int absolute_blocks;    /* absolute block count */
};

/* default memory pool configuration: 100% in pool 0 */
static struct mem_pool_config sc_mem_pool_config[NUM_SC_POOLS] = {
        /* centi%, abs blocks */
        {  10000,     -1 },             /* pool 0 */
        {      0,     -1 },             /* pool 1 */
};

/* memory pool information, used when calculating final sizes */
struct mem_pool_info {
        int centipercent;       /*
                                 * 100th of 1% of memory to use, -1 if blocks
                                 * already set
                                 */
        int count;              /* count of contexts in the pool */
        int blocks;             /* block size of the pool */
        int size;               /* context size, in blocks */
};

/*
 * Convert a pool wildcard to a valid pool index.  The wildcards
 * start at -1 and increase negatively.  Map them as:
 *      -1 => 0
 *      -2 => 1
 *      etc.
 *
 * Return -1 on non-wildcard input, otherwise convert to a pool number.
 */
static int wildcard_to_pool(int wc)
{
        if (wc >= 0)
                return -1;      /* non-wildcard */
        return -wc - 1;
}

static const char *sc_type_names[SC_MAX] = {
        "kernel",
        "ack",
        "user",
        "vl15"
};

static const char *sc_type_name(int index)
{
        if (index < 0 || index >= SC_MAX)
                return "unknown";
        return sc_type_names[index];
}

/*
 * Read the send context memory pool configuration and send context
 * size configuration.  Replace any wildcards and come up with final
 * counts and sizes for the send context types.
 */
int init_sc_pools_and_sizes(struct hfi1_devdata *dd)
{
        struct mem_pool_info mem_pool_info[NUM_SC_POOLS] = { { 0 } };
        int total_blocks = (dd->chip_pio_mem_size / PIO_BLOCK_SIZE) - 1;
        int total_contexts = 0;
        int fixed_blocks;
        int pool_blocks;
        int used_blocks;
        int cp_total;           /* centipercent total */
        int ab_total;           /* absolute block total */
        int extra;
        int i;

        /*
         * When SDMA is enabled, kernel context pio packet size is capped by
         * "piothreshold". Reduce pio buffer allocation for kernel context by
         * setting it to a fixed size. The allocation allows 3-deep buffering
         * of the largest pio packets plus up to 128 bytes header, sufficient
         * to maintain verbs performance.
         *
         * When SDMA is disabled, keep the default pooling allocation.
         */
        if (HFI1_CAP_IS_KSET(SDMA)) {
                u16 max_pkt_size = (piothreshold < PIO_THRESHOLD_CEILING) ?
                                         piothreshold : PIO_THRESHOLD_CEILING;
                sc_config_sizes[SC_KERNEL].size =
                        3 * (max_pkt_size + 128) / PIO_BLOCK_SIZE;
        }

        /*
         * Step 0:
         *      - copy the centipercents/absolute sizes from the pool config
         *      - sanity check these values
         *      - add up centipercents, then later check for full value
         *      - add up absolute blocks, then later check for over-commit
         */
        cp_total = 0;
        ab_total = 0;
        for (i = 0; i < NUM_SC_POOLS; i++) {
                int cp = sc_mem_pool_config[i].centipercent;
                int ab = sc_mem_pool_config[i].absolute_blocks;

                /*
                 * A negative value is "unused" or "invalid".  Both *can*
                 * be valid, but centipercent wins, so check that first
                 */
                if (cp >= 0) {                  /* centipercent valid */
                        cp_total += cp;
                } else if (ab >= 0) {           /* absolute blocks valid */
                        ab_total += ab;
                } else {                        /* neither valid */
                        dd_dev_err(
                                dd,
                                "Send context memory pool %d: both the block count and centipercent are invalid\n",
                                i);
                        return -EINVAL;
                }

                mem_pool_info[i].centipercent = cp;
                mem_pool_info[i].blocks = ab;
        }

        /* do not use both % and absolute blocks for different pools */
        if (cp_total != 0 && ab_total != 0) {
                dd_dev_err(
                        dd,
                        "All send context memory pools must be described as either centipercent or blocks, no mixing between pools\n");
                return -EINVAL;
        }

        /* if any percentages are present, they must add up to 100% x 100 */
        if (cp_total != 0 && cp_total != 10000) {
                dd_dev_err(
                        dd,
                        "Send context memory pool centipercent is %d, expecting 10000\n",
                        cp_total);
                return -EINVAL;
        }

        /* the absolute pool total cannot be more than the mem total */
        if (ab_total > total_blocks) {
                dd_dev_err(
                        dd,
                        "Send context memory pool absolute block count %d is larger than the memory size %d\n",
                        ab_total, total_blocks);
                return -EINVAL;
        }

        /*
         * Step 2:
         *      - copy from the context size config
         *      - replace context type wildcard counts with real values
         *      - add up non-memory pool block sizes
         *      - add up memory pool user counts
         */
        fixed_blocks = 0;
        for (i = 0; i < SC_MAX; i++) {
                int count = sc_config_sizes[i].count;
                int size = sc_config_sizes[i].size;
                int pool;

                /*
                 * Sanity check count: Either a positive value or
                 * one of the expected wildcards is valid.  The positive
                 * value is checked later when we compare against total
                 * memory available.
                 */
                if (i == SC_ACK) {
                        count = dd->n_krcv_queues;
                } else if (i == SC_KERNEL) {
                        count = INIT_SC_PER_VL * num_vls;
                } else if (count == SCC_PER_CPU) {
                        count = dd->num_rcv_contexts - dd->n_krcv_queues;
                } else if (count < 0) {
                        dd_dev_err(
                                dd,
                                "%s send context invalid count wildcard %d\n",
                                sc_type_name(i), count);
                        return -EINVAL;
                }
                if (total_contexts + count > dd->chip_send_contexts)
                        count = dd->chip_send_contexts - total_contexts;

                total_contexts += count;

                /*
                 * Sanity check pool: The conversion will return a pool
                 * number or -1 if a fixed (non-negative) value.  The fixed
                 * value is checked later when we compare against
                 * total memory available.
                 */
                pool = wildcard_to_pool(size);
                if (pool == -1) {                       /* non-wildcard */
                        fixed_blocks += size * count;
                } else if (pool < NUM_SC_POOLS) {       /* valid wildcard */
                        mem_pool_info[pool].count += count;
                } else {                                /* invalid wildcard */
                        dd_dev_err(
                                dd,
                                "%s send context invalid pool wildcard %d\n",
                                sc_type_name(i), size);
                        return -EINVAL;
                }

                dd->sc_sizes[i].count = count;
                dd->sc_sizes[i].size = size;
        }
        if (fixed_blocks > total_blocks) {
                dd_dev_err(
                        dd,
                        "Send context fixed block count, %u, larger than total block count %u\n",
                        fixed_blocks, total_blocks);
                return -EINVAL;
        }

        /* step 3: calculate the blocks in the pools, and pool context sizes */
        pool_blocks = total_blocks - fixed_blocks;
        if (ab_total > pool_blocks) {
                dd_dev_err(
                        dd,
                        "Send context fixed pool sizes, %u, larger than pool block count %u\n",
                        ab_total, pool_blocks);
                return -EINVAL;
        }
        /* subtract off the fixed pool blocks */
        pool_blocks -= ab_total;

        for (i = 0; i < NUM_SC_POOLS; i++) {
                struct mem_pool_info *pi = &mem_pool_info[i];

                /* % beats absolute blocks */
                if (pi->centipercent >= 0)
                        pi->blocks = (pool_blocks * pi->centipercent) / 10000;

                if (pi->blocks == 0 && pi->count != 0) {
                        dd_dev_err(
                                dd,
                                "Send context memory pool %d has %u contexts, but no blocks\n",
                                i, pi->count);
                        return -EINVAL;
                }
                if (pi->count == 0) {
                        /* warn about wasted blocks */
                        if (pi->blocks != 0)
                                dd_dev_err(
                                        dd,
                                        "Send context memory pool %d has %u blocks, but zero contexts\n",
                                        i, pi->blocks);
                        pi->size = 0;
                } else {
                        pi->size = pi->blocks / pi->count;
                }
        }

        /* step 4: fill in the context type sizes from the pool sizes */
        used_blocks = 0;
        for (i = 0; i < SC_MAX; i++) {
                if (dd->sc_sizes[i].size < 0) {
                        unsigned pool = wildcard_to_pool(dd->sc_sizes[i].size);

                        WARN_ON_ONCE(pool >= NUM_SC_POOLS);
                        dd->sc_sizes[i].size = mem_pool_info[pool].size;
                }
                /* make sure we are not larger than what is allowed by the HW */
#define PIO_MAX_BLOCKS 1024
                if (dd->sc_sizes[i].size > PIO_MAX_BLOCKS)
                        dd->sc_sizes[i].size = PIO_MAX_BLOCKS;

                /* calculate our total usage */
                used_blocks += dd->sc_sizes[i].size * dd->sc_sizes[i].count;
        }
        extra = total_blocks - used_blocks;
        if (extra != 0)
                dd_dev_info(dd, "unused send context blocks: %d\n", extra);

        return total_contexts;
}

int init_send_contexts(struct hfi1_devdata *dd)
{
        u16 base;
        int ret, i, j, context;

        ret = init_credit_return(dd);
        if (ret)
                return ret;

        dd->hw_to_sw = kmalloc_array(TXE_NUM_CONTEXTS, sizeof(u8),
                                        GFP_KERNEL);
        dd->send_contexts = kcalloc(dd->num_send_contexts,
                                    sizeof(struct send_context_info),
                                    GFP_KERNEL);
        if (!dd->send_contexts || !dd->hw_to_sw) {
                kfree(dd->hw_to_sw);
                kfree(dd->send_contexts);
                free_credit_return(dd);
                return -ENOMEM;
        }

        /* hardware context map starts with invalid send context indices */
        for (i = 0; i < TXE_NUM_CONTEXTS; i++)
                dd->hw_to_sw[i] = INVALID_SCI;

        /*
         * All send contexts have their credit sizes.  Allocate credits
         * for each context one after another from the global space.
         */
        context = 0;
        base = 1;
        for (i = 0; i < SC_MAX; i++) {
                struct sc_config_sizes *scs = &dd->sc_sizes[i];

                for (j = 0; j < scs->count; j++) {
                        struct send_context_info *sci =
                                                &dd->send_contexts[context];
                        sci->type = i;
                        sci->base = base;
                        sci->credits = scs->size;

                        context++;
                        base += scs->size;
                }
        }

        return 0;
}

/*
 * Allocate a software index and hardware context of the given type.
 *
 * Must be called with dd->sc_lock held.
 */
static int sc_hw_alloc(struct hfi1_devdata *dd, int type, u32 *sw_index,
                       u32 *hw_context)
{
        struct send_context_info *sci;
        u32 index;
        u32 context;

        for (index = 0, sci = &dd->send_contexts[0];
                        index < dd->num_send_contexts; index++, sci++) {
                if (sci->type == type && sci->allocated == 0) {
                        sci->allocated = 1;
                        /* use a 1:1 mapping, but make them non-equal */
                        context = dd->chip_send_contexts - index - 1;
                        dd->hw_to_sw[context] = index;
                        *sw_index = index;
                        *hw_context = context;
                        return 0; /* success */
                }
        }
        dd_dev_err(dd, "Unable to locate a free type %d send context\n", type);
        return -ENOSPC;
}

/*
 * Free the send context given by its software index.
 *
 * Must be called with dd->sc_lock held.
 */
static void sc_hw_free(struct hfi1_devdata *dd, u32 sw_index, u32 hw_context)
{
        struct send_context_info *sci;

        sci = &dd->send_contexts[sw_index];
        if (!sci->allocated) {
                dd_dev_err(dd, "%s: sw_index %u not allocated? hw_context %u\n",
                           __func__, sw_index, hw_context);
        }
        sci->allocated = 0;
        dd->hw_to_sw[hw_context] = INVALID_SCI;
}

/* return the base context of a context in a group */
static inline u32 group_context(u32 context, u32 group)
{
        return (context >> group) << group;
}

/* return the size of a group */
static inline u32 group_size(u32 group)
{
        return 1 << group;
}

/*
 * Obtain the credit return addresses, kernel virtual and bus, for the
 * given sc.
 *
 * To understand this routine:
 * o va and dma are arrays of struct credit_return.  One for each physical
 *   send context, per NUMA.
 * o Each send context always looks in its relative location in a struct
 *   credit_return for its credit return.
 * o Each send context in a group must have its return address CSR programmed
 *   with the same value.  Use the address of the first send context in the
 *   group.
 */
static void cr_group_addresses(struct send_context *sc, dma_addr_t *dma)
{
        u32 gc = group_context(sc->hw_context, sc->group);
        u32 index = sc->hw_context & 0x7;

        sc->hw_free = &sc->dd->cr_base[sc->node].va[gc].cr[index];
        *dma = (unsigned long)
               &((struct credit_return *)sc->dd->cr_base[sc->node].dma)[gc];
}

/*
 * Work queue function triggered in error interrupt routine for
 * kernel contexts.
 */
static void sc_halted(struct work_struct *work)
{
        struct send_context *sc;

        sc = container_of(work, struct send_context, halt_work);
        sc_restart(sc);
}

/*
 * Calculate PIO block threshold for this send context using the given MTU.
 * Trigger a return when one MTU plus optional header of credits remain.
 *
 * Parameter mtu is in bytes.
 * Parameter hdrqentsize is in DWORDs.
 *
 * Return value is what to write into the CSR: trigger return when
 * unreturned credits pass this count.
 */
u32 sc_mtu_to_threshold(struct send_context *sc, u32 mtu, u32 hdrqentsize)
{
        u32 release_credits;
        u32 threshold;

        /* add in the header size, then divide by the PIO block size */
        mtu += hdrqentsize << 2;
        release_credits = DIV_ROUND_UP(mtu, PIO_BLOCK_SIZE);

        /* check against this context's credits */
        if (sc->credits <= release_credits)
                threshold = 1;
        else
                threshold = sc->credits - release_credits;

        return threshold;
}

/*
 * Calculate credit threshold in terms of percent of the allocated credits.
 * Trigger when unreturned credits equal or exceed the percentage of the whole.
 *
 * Return value is what to write into the CSR: trigger return when
 * unreturned credits pass this count.
 */
u32 sc_percent_to_threshold(struct send_context *sc, u32 percent)
{
        return (sc->credits * percent) / 100;
}

/*
 * Set the credit return threshold.
 */
void sc_set_cr_threshold(struct send_context *sc, u32 new_threshold)
{
        unsigned long flags;
        u32 old_threshold;
        int force_return = 0;

        spin_lock_irqsave(&sc->credit_ctrl_lock, flags);

        old_threshold = (sc->credit_ctrl >>
                                SC(CREDIT_CTRL_THRESHOLD_SHIFT))
                         & SC(CREDIT_CTRL_THRESHOLD_MASK);

        if (new_threshold != old_threshold) {
                sc->credit_ctrl =
                        (sc->credit_ctrl
                                & ~SC(CREDIT_CTRL_THRESHOLD_SMASK))
                        | ((new_threshold
                                & SC(CREDIT_CTRL_THRESHOLD_MASK))
                           << SC(CREDIT_CTRL_THRESHOLD_SHIFT));
                write_kctxt_csr(sc->dd, sc->hw_context,
                                SC(CREDIT_CTRL), sc->credit_ctrl);

                /* force a credit return on change to avoid a possible stall */
                force_return = 1;
        }

        spin_unlock_irqrestore(&sc->credit_ctrl_lock, flags);

        if (force_return)
                sc_return_credits(sc);
}

/*
 * set_pio_integrity
 *
 * Set the CHECK_ENABLE register for the send context 'sc'.
 */
void set_pio_integrity(struct send_context *sc)
{
        struct hfi1_devdata *dd = sc->dd;
        u32 hw_context = sc->hw_context;
        int type = sc->type;

        write_kctxt_csr(dd, hw_context,
                        SC(CHECK_ENABLE),
                        hfi1_pkt_default_send_ctxt_mask(dd, type));
}

static u32 get_buffers_allocated(struct send_context *sc)
{
        int cpu;
        u32 ret = 0;

        for_each_possible_cpu(cpu)
                ret += *per_cpu_ptr(sc->buffers_allocated, cpu);
        return ret;
}

static void reset_buffers_allocated(struct send_context *sc)
{
        int cpu;

        for_each_possible_cpu(cpu)
                (*per_cpu_ptr(sc->buffers_allocated, cpu)) = 0;
}

/*
 * Allocate a NUMA relative send context structure of the given type along
 * with a HW context.
 */
struct send_context *sc_alloc(struct hfi1_devdata *dd, int type,
                              uint hdrqentsize, int numa)
{
        struct send_context_info *sci;
        struct send_context *sc = NULL;
        dma_addr_t dma;
        unsigned long flags;
        u64 reg;
        u32 thresh;
        u32 sw_index;
        u32 hw_context;
        int ret;
        u8 opval, opmask;

        /* do not allocate while frozen */
        if (dd->flags & HFI1_FROZEN)
                return NULL;

        sc = kzalloc_node(sizeof(*sc), GFP_KERNEL, numa);
        if (!sc)
                return NULL;

        sc->buffers_allocated = alloc_percpu(u32);
        if (!sc->buffers_allocated) {
                kfree(sc);
                dd_dev_err(dd,
                           "Cannot allocate buffers_allocated per cpu counters\n"
                          );
                return NULL;
        }

        spin_lock_irqsave(&dd->sc_lock, flags);
        ret = sc_hw_alloc(dd, type, &sw_index, &hw_context);
        if (ret) {
                spin_unlock_irqrestore(&dd->sc_lock, flags);
                free_percpu(sc->buffers_allocated);
                kfree(sc);
                return NULL;
        }

        sci = &dd->send_contexts[sw_index];
        sci->sc = sc;

        sc->dd = dd;
        sc->node = numa;
        sc->type = type;
        spin_lock_init(&sc->alloc_lock);
        spin_lock_init(&sc->release_lock);
        spin_lock_init(&sc->credit_ctrl_lock);
        INIT_LIST_HEAD(&sc->piowait);
        INIT_WORK(&sc->halt_work, sc_halted);
        init_waitqueue_head(&sc->halt_wait);

        /* grouping is always single context for now */
        sc->group = 0;

        sc->sw_index = sw_index;
        sc->hw_context = hw_context;
        cr_group_addresses(sc, &dma);
        sc->credits = sci->credits;
        sc->size = sc->credits * PIO_BLOCK_SIZE;

/* PIO Send Memory Address details */
#define PIO_ADDR_CONTEXT_MASK 0xfful
#define PIO_ADDR_CONTEXT_SHIFT 16
        sc->base_addr = dd->piobase + ((hw_context & PIO_ADDR_CONTEXT_MASK)
                                        << PIO_ADDR_CONTEXT_SHIFT);

        /* set base and credits */
        reg = ((sci->credits & SC(CTRL_CTXT_DEPTH_MASK))
                                        << SC(CTRL_CTXT_DEPTH_SHIFT))
                | ((sci->base & SC(CTRL_CTXT_BASE_MASK))
                                        << SC(CTRL_CTXT_BASE_SHIFT));
        write_kctxt_csr(dd, hw_context, SC(CTRL), reg);

        set_pio_integrity(sc);

        /* unmask all errors */
        write_kctxt_csr(dd, hw_context, SC(ERR_MASK), (u64)-1);

        /* set the default partition key */
        write_kctxt_csr(dd, hw_context, SC(CHECK_PARTITION_KEY),
                        (SC(CHECK_PARTITION_KEY_VALUE_MASK) &
                         DEFAULT_PKEY) <<
                        SC(CHECK_PARTITION_KEY_VALUE_SHIFT));

        /* per context type checks */
        if (type == SC_USER) {
                opval = USER_OPCODE_CHECK_VAL;
                opmask = USER_OPCODE_CHECK_MASK;
        } else {
                opval = OPCODE_CHECK_VAL_DISABLED;
                opmask = OPCODE_CHECK_MASK_DISABLED;
        }

        /* set the send context check opcode mask and value */
        write_kctxt_csr(dd, hw_context, SC(CHECK_OPCODE),
                        ((u64)opmask << SC(CHECK_OPCODE_MASK_SHIFT)) |
                        ((u64)opval << SC(CHECK_OPCODE_VALUE_SHIFT)));

        /* set up credit return */
        reg = dma & SC(CREDIT_RETURN_ADDR_ADDRESS_SMASK);
        write_kctxt_csr(dd, hw_context, SC(CREDIT_RETURN_ADDR), reg);

        /*
         * Calculate the initial credit return threshold.
         *
         * For Ack contexts, set a threshold for half the credits.
         * For User contexts use the given percentage.  This has been
         * sanitized on driver start-up.
         * For Kernel contexts, use the default MTU plus a header
         * or half the credits, whichever is smaller. This should
         * work for both the 3-deep buffering allocation and the
         * pooling allocation.
         */
        if (type == SC_ACK) {
                thresh = sc_percent_to_threshold(sc, 50);
        } else if (type == SC_USER) {
                thresh = sc_percent_to_threshold(sc,
                                                 user_credit_return_threshold);
        } else { /* kernel */
                thresh = min(sc_percent_to_threshold(sc, 50),
                             sc_mtu_to_threshold(sc, hfi1_max_mtu,
                                                 hdrqentsize));
        }
        reg = thresh << SC(CREDIT_CTRL_THRESHOLD_SHIFT);
        /* add in early return */
        if (type == SC_USER && HFI1_CAP_IS_USET(EARLY_CREDIT_RETURN))
                reg |= SC(CREDIT_CTRL_EARLY_RETURN_SMASK);
        else if (HFI1_CAP_IS_KSET(EARLY_CREDIT_RETURN)) /* kernel, ack */
                reg |= SC(CREDIT_CTRL_EARLY_RETURN_SMASK);

        /* set up write-through credit_ctrl */
        sc->credit_ctrl = reg;
        write_kctxt_csr(dd, hw_context, SC(CREDIT_CTRL), reg);

        /* User send contexts should not allow sending on VL15 */
        if (type == SC_USER) {
                reg = 1ULL << 15;
                write_kctxt_csr(dd, hw_context, SC(CHECK_VL), reg);
        }

        spin_unlock_irqrestore(&dd->sc_lock, flags);

        /*
         * Allocate shadow ring to track outstanding PIO buffers _after_
         * unlocking.  We don't know the size until the lock is held and
         * we can't allocate while the lock is held.  No one is using
         * the context yet, so allocate it now.
         *
         * User contexts do not get a shadow ring.
         */
        if (type != SC_USER) {
                /*
                 * Size the shadow ring 1 larger than the number of credits
                 * so head == tail can mean empty.
                 */
                sc->sr_size = sci->credits + 1;
                sc->sr = kcalloc_node(sc->sr_size,
                                      sizeof(union pio_shadow_ring),
                                      GFP_KERNEL, numa);
                if (!sc->sr) {
                        sc_free(sc);
                        return NULL;
                }
        }

        hfi1_cdbg(PIO,
                  "Send context %u(%u) %s group %u credits %u credit_ctrl 0x%llx threshold %u\n",
                  sw_index,
                  hw_context,
                  sc_type_name(type),
                  sc->group,
                  sc->credits,
                  sc->credit_ctrl,
                  thresh);

        return sc;
}

/* free a per-NUMA send context structure */
void sc_free(struct send_context *sc)
{
        struct hfi1_devdata *dd;
        unsigned long flags;
        u32 sw_index;
        u32 hw_context;

        if (!sc)
                return;

        sc->flags |= SCF_IN_FREE;       /* ensure no restarts */
        dd = sc->dd;
        if (!list_empty(&sc->piowait))
                dd_dev_err(dd, "piowait list not empty!\n");
        sw_index = sc->sw_index;
        hw_context = sc->hw_context;
        sc_disable(sc); /* make sure the HW is disabled */
        flush_work(&sc->halt_work);

        spin_lock_irqsave(&dd->sc_lock, flags);
        dd->send_contexts[sw_index].sc = NULL;

        /* clear/disable all registers set in sc_alloc */
        write_kctxt_csr(dd, hw_context, SC(CTRL), 0);
        write_kctxt_csr(dd, hw_context, SC(CHECK_ENABLE), 0);
        write_kctxt_csr(dd, hw_context, SC(ERR_MASK), 0);
        write_kctxt_csr(dd, hw_context, SC(CHECK_PARTITION_KEY), 0);
        write_kctxt_csr(dd, hw_context, SC(CHECK_OPCODE), 0);
        write_kctxt_csr(dd, hw_context, SC(CREDIT_RETURN_ADDR), 0);
        write_kctxt_csr(dd, hw_context, SC(CREDIT_CTRL), 0);

        /* release the index and context for re-use */
        sc_hw_free(dd, sw_index, hw_context);
        spin_unlock_irqrestore(&dd->sc_lock, flags);

        kfree(sc->sr);
        free_percpu(sc->buffers_allocated);
        kfree(sc);
}

/* disable the context */
void sc_disable(struct send_context *sc)
{
        u64 reg;
        unsigned long flags;
        struct pio_buf *pbuf;

        if (!sc)
                return;

        /* do all steps, even if already disabled */
        spin_lock_irqsave(&sc->alloc_lock, flags);
        reg = read_kctxt_csr(sc->dd, sc->hw_context, SC(CTRL));
        reg &= ~SC(CTRL_CTXT_ENABLE_SMASK);
        sc->flags &= ~SCF_ENABLED;
        sc_wait_for_packet_egress(sc, 1);
        write_kctxt_csr(sc->dd, sc->hw_context, SC(CTRL), reg);
        spin_unlock_irqrestore(&sc->alloc_lock, flags);

        /*
         * Flush any waiters.  Once the context is disabled,
         * credit return interrupts are stopped (although there
         * could be one in-process when the context is disabled).
         * Wait one microsecond for any lingering interrupts, then
         * proceed with the flush.
         */
        udelay(1);
        spin_lock_irqsave(&sc->release_lock, flags);
        if (sc->sr) {   /* this context has a shadow ring */
                while (sc->sr_tail != sc->sr_head) {
                        pbuf = &sc->sr[sc->sr_tail].pbuf;
                        if (pbuf->cb)
                                (*pbuf->cb)(pbuf->arg, PRC_SC_DISABLE);
                        sc->sr_tail++;
                        if (sc->sr_tail >= sc->sr_size)
                                sc->sr_tail = 0;
                }
        }
        spin_unlock_irqrestore(&sc->release_lock, flags);
}

/* return SendEgressCtxtStatus.PacketOccupancy */
#define packet_occupancy(r) \
        (((r) & SEND_EGRESS_CTXT_STATUS_CTXT_EGRESS_PACKET_OCCUPANCY_SMASK)\
        >> SEND_EGRESS_CTXT_STATUS_CTXT_EGRESS_PACKET_OCCUPANCY_SHIFT)

/* is egress halted on the context? */
#define egress_halted(r) \
        ((r) & SEND_EGRESS_CTXT_STATUS_CTXT_EGRESS_HALT_STATUS_SMASK)

/* wait for packet egress, optionally pause for credit return  */
static void sc_wait_for_packet_egress(struct send_context *sc, int pause)
{
        struct hfi1_devdata *dd = sc->dd;
        u64 reg = 0;
        u64 reg_prev;
        u32 loop = 0;

        while (1) {
                reg_prev = reg;
                reg = read_csr(dd, sc->hw_context * 8 +
                               SEND_EGRESS_CTXT_STATUS);
                /* done if egress is stopped */
                if (egress_halted(reg))
                        break;
                reg = packet_occupancy(reg);
                if (reg == 0)
                        break;
                /* counter is reset if occupancy count changes */
                if (reg != reg_prev)
                        loop = 0;
                if (loop > 50000) {
                        /* timed out - bounce the link */
                        dd_dev_err(dd,
                                   "%s: context %u(%u) timeout waiting for packets to egress, remaining count %u, bouncing link\n",
                                   __func__, sc->sw_index,
                                   sc->hw_context, (u32)reg);
                        queue_work(dd->pport->link_wq,
                                   &dd->pport->link_bounce_work);
                        break;
                }
                loop++;
                udelay(1);
        }

        if (pause)
                /* Add additional delay to ensure chip returns all credits */
                pause_for_credit_return(dd);
}

void sc_wait(struct hfi1_devdata *dd)
{
        int i;

        for (i = 0; i < dd->num_send_contexts; i++) {
                struct send_context *sc = dd->send_contexts[i].sc;

                if (!sc)
                        continue;
                sc_wait_for_packet_egress(sc, 0);
        }
}

/*
 * Restart a context after it has been halted due to error.
 *
 * If the first step fails - wait for the halt to be asserted, return early.
 * Otherwise complain about timeouts but keep going.
 *
 * It is expected that allocations (enabled flag bit) have been shut off
 * already (only applies to kernel contexts).
 */
int sc_restart(struct send_context *sc)
{
        struct hfi1_devdata *dd = sc->dd;
        u64 reg;
        u32 loop;
        int count;

        /* bounce off if not halted, or being free'd */
        if (!(sc->flags & SCF_HALTED) || (sc->flags & SCF_IN_FREE))
                return -EINVAL;

        dd_dev_info(dd, "restarting send context %u(%u)\n", sc->sw_index,
                    sc->hw_context);

        /*
         * Step 1: Wait for the context to actually halt.
         *
         * The error interrupt is asynchronous to actually setting halt
         * on the context.
         */
        loop = 0;
        while (1) {
                reg = read_kctxt_csr(dd, sc->hw_context, SC(STATUS));
                if (reg & SC(STATUS_CTXT_HALTED_SMASK))
                        break;
                if (loop > 100) {
                        dd_dev_err(dd, "%s: context %u(%u) not halting, skipping\n",
                                   __func__, sc->sw_index, sc->hw_context);
                        return -ETIME;
                }
                loop++;
                udelay(1);
        }

        /*
         * Step 2: Ensure no users are still trying to write to PIO.
         *
         * For kernel contexts, we have already turned off buffer allocation.
         * Now wait for the buffer count to go to zero.
         *
         * For user contexts, the user handling code has cut off write access
         * to the context's PIO pages before calling this routine and will
         * restore write access after this routine returns.
         */
        if (sc->type != SC_USER) {
                /* kernel context */
                loop = 0;
                while (1) {
                        count = get_buffers_allocated(sc);
                        if (count == 0)
                                break;
                        if (loop > 100) {
                                dd_dev_err(dd,
                                           "%s: context %u(%u) timeout waiting for PIO buffers to zero, remaining %d\n",
                                           __func__, sc->sw_index,
                                           sc->hw_context, count);
                        }
                        loop++;
                        udelay(1);
                }
        }

        /*
         * Step 3: Wait for all packets to egress.
         * This is done while disabling the send context
         *
         * Step 4: Disable the context
         *
         * This is a superset of the halt.  After the disable, the
         * errors can be cleared.
         */
        sc_disable(sc);

        /*
         * Step 5: Enable the context
         *
         * This enable will clear the halted flag and per-send context
         * error flags.
         */
        return sc_enable(sc);
}

/*
 * PIO freeze processing.  To be called after the TXE block is fully frozen.
 * Go through all frozen send contexts and disable them.  The contexts are
 * already stopped by the freeze.
 */
void pio_freeze(struct hfi1_devdata *dd)
{
        struct send_context *sc;
        int i;

        for (i = 0; i < dd->num_send_contexts; i++) {
                sc = dd->send_contexts[i].sc;
                /*
                 * Don't disable unallocated, unfrozen, or user send contexts.
                 * User send contexts will be disabled when the process
                 * calls into the driver to reset its context.
                 */
                if (!sc || !(sc->flags & SCF_FROZEN) || sc->type == SC_USER)
                        continue;

                /* only need to disable, the context is already stopped */
                sc_disable(sc);
        }
}

/*
 * Unfreeze PIO for kernel send contexts.  The precondition for calling this
 * is that all PIO send contexts have been disabled and the SPC freeze has
 * been cleared.  Now perform the last step and re-enable each kernel context.
 * User (PSM) processing will occur when PSM calls into the kernel to
 * acknowledge the freeze.
 */
void pio_kernel_unfreeze(struct hfi1_devdata *dd)
{
        struct send_context *sc;
        int i;

        for (i = 0; i < dd->num_send_contexts; i++) {
                sc = dd->send_contexts[i].sc;
                if (!sc || !(sc->flags & SCF_FROZEN) || sc->type == SC_USER)
                        continue;

                sc_enable(sc);  /* will clear the sc frozen flag */
        }
}

/*
 * Wait for the SendPioInitCtxt.PioInitInProgress bit to clear.
 * Returns:
 *      -ETIMEDOUT - if we wait too long
 *      -EIO       - if there was an error
 */
static int pio_init_wait_progress(struct hfi1_devdata *dd)
{
        u64 reg;
        int max, count = 0;

        /* max is the longest possible HW init time / delay */
        max = (dd->icode == ICODE_FPGA_EMULATION) ? 120 : 5;
        while (1) {
                reg = read_csr(dd, SEND_PIO_INIT_CTXT);
                if (!(reg & SEND_PIO_INIT_CTXT_PIO_INIT_IN_PROGRESS_SMASK))
                        break;
                if (count >= max)
                        return -ETIMEDOUT;
                udelay(5);
                count++;
        }

        return reg & SEND_PIO_INIT_CTXT_PIO_INIT_ERR_SMASK ? -EIO : 0;
}

/*
 * Reset all of the send contexts to their power-on state.  Used
 * only during manual init - no lock against sc_enable needed.
 */
void pio_reset_all(struct hfi1_devdata *dd)
{
        int ret;

        /* make sure the init engine is not busy */
        ret = pio_init_wait_progress(dd);
        /* ignore any timeout */
        if (ret == -EIO) {
                /* clear the error */
                write_csr(dd, SEND_PIO_ERR_CLEAR,
                          SEND_PIO_ERR_CLEAR_PIO_INIT_SM_IN_ERR_SMASK);
        }

        /* reset init all */
        write_csr(dd, SEND_PIO_INIT_CTXT,
                  SEND_PIO_INIT_CTXT_PIO_ALL_CTXT_INIT_SMASK);
        udelay(2);
        ret = pio_init_wait_progress(dd);
        if (ret < 0) {
                dd_dev_err(dd,
                           "PIO send context init %s while initializing all PIO blocks\n",
                           ret == -ETIMEDOUT ? "is stuck" : "had an error");
        }
}

/* enable the context */
int sc_enable(struct send_context *sc)
{
        u64 sc_ctrl, reg, pio;
        struct hfi1_devdata *dd;
        unsigned long flags;
        int ret = 0;

        if (!sc)
                return -EINVAL;
        dd = sc->dd;

        /*
         * Obtain the allocator lock to guard against any allocation
         * attempts (which should not happen prior to context being
         * enabled). On the release/disable side we don't need to
         * worry about locking since the releaser will not do anything
         * if the context accounting values have not changed.
         */
        spin_lock_irqsave(&sc->alloc_lock, flags);
        sc_ctrl = read_kctxt_csr(dd, sc->hw_context, SC(CTRL));
        if ((sc_ctrl & SC(CTRL_CTXT_ENABLE_SMASK)))
                goto unlock; /* already enabled */

        /* IMPORTANT: only clear free and fill if transitioning 0 -> 1 */

        *sc->hw_free = 0;
        sc->free = 0;
        sc->alloc_free = 0;
        sc->fill = 0;
        sc->fill_wrap = 0;
        sc->sr_head = 0;
        sc->sr_tail = 0;
        sc->flags = 0;
        /* the alloc lock insures no fast path allocation */
        reset_buffers_allocated(sc);

        /*
         * Clear all per-context errors.  Some of these will be set when
         * we are re-enabling after a context halt.  Now that the context
         * is disabled, the halt will not clear until after the PIO init
         * engine runs below.
         */
        reg = read_kctxt_csr(dd, sc->hw_context, SC(ERR_STATUS));
        if (reg)
                write_kctxt_csr(dd, sc->hw_context, SC(ERR_CLEAR), reg);

        /*
         * The HW PIO initialization engine can handle only one init
         * request at a time. Serialize access to each device's engine.
         */
        spin_lock(&dd->sc_init_lock);
        /*
         * Since access to this code block is serialized and
         * each access waits for the initialization to complete
         * before releasing the lock, the PIO initialization engine
         * should not be in use, so we don't have to wait for the
         * InProgress bit to go down.
         */
        pio = ((sc->hw_context & SEND_PIO_INIT_CTXT_PIO_CTXT_NUM_MASK) <<
               SEND_PIO_INIT_CTXT_PIO_CTXT_NUM_SHIFT) |
                SEND_PIO_INIT_CTXT_PIO_SINGLE_CTXT_INIT_SMASK;
        write_csr(dd, SEND_PIO_INIT_CTXT, pio);
        /*
         * Wait until the engine is done.  Give the chip the required time
         * so, hopefully, we read the register just once.
         */
        udelay(2);
        ret = pio_init_wait_progress(dd);
        spin_unlock(&dd->sc_init_lock);
        if (ret) {
                dd_dev_err(dd,
                           "sctxt%u(%u): Context not enabled due to init failure %d\n",
                           sc->sw_index, sc->hw_context, ret);
                goto unlock;
        }

        /*
         * All is well. Enable the context.
         */
        sc_ctrl |= SC(CTRL_CTXT_ENABLE_SMASK);
        write_kctxt_csr(dd, sc->hw_context, SC(CTRL), sc_ctrl);
        /*
         * Read SendCtxtCtrl to force the write out and prevent a timing
         * hazard where a PIO write may reach the context before the enable.
         */
        read_kctxt_csr(dd, sc->hw_context, SC(CTRL));
        sc->flags |= SCF_ENABLED;

unlock:
        spin_unlock_irqrestore(&sc->alloc_lock, flags);

        return ret;
}

/* force a credit return on the context */
void sc_return_credits(struct send_context *sc)
{
        if (!sc)
                return;

        /* a 0->1 transition schedules a credit return */
        write_kctxt_csr(sc->dd, sc->hw_context, SC(CREDIT_FORCE),
                        SC(CREDIT_FORCE_FORCE_RETURN_SMASK));
        /*
         * Ensure that the write is flushed and the credit return is
         * scheduled. We care more about the 0 -> 1 transition.
         */
        read_kctxt_csr(sc->dd, sc->hw_context, SC(CREDIT_FORCE));
        /* set back to 0 for next time */
        write_kctxt_csr(sc->dd, sc->hw_context, SC(CREDIT_FORCE), 0);
}

/* allow all in-flight packets to drain on the context */
void sc_flush(struct send_context *sc)
{
        if (!sc)
                return;

        sc_wait_for_packet_egress(sc, 1);
}

/* drop all packets on the context, no waiting until they are sent */
void sc_drop(struct send_context *sc)
{
        if (!sc)
                return;

        dd_dev_info(sc->dd, "%s: context %u(%u) - not implemented\n",
                    __func__, sc->sw_index, sc->hw_context);
}

/*
 * Start the software reaction to a context halt or SPC freeze:
 *      - mark the context as halted or frozen
 *      - stop buffer allocations
 *
 * Called from the error interrupt.  Other work is deferred until
 * out of the interrupt.
 */
void sc_stop(struct send_context *sc, int flag)
{
        unsigned long flags;

        /* mark the context */
        sc->flags |= flag;

        /* stop buffer allocations */
        spin_lock_irqsave(&sc->alloc_lock, flags);
        sc->flags &= ~SCF_ENABLED;
        spin_unlock_irqrestore(&sc->alloc_lock, flags);
        wake_up(&sc->halt_wait);
}

#define BLOCK_DWORDS (PIO_BLOCK_SIZE / sizeof(u32))
#define dwords_to_blocks(x) DIV_ROUND_UP(x, BLOCK_DWORDS)

/*
 * The send context buffer "allocator".
 *
 * @sc: the PIO send context we are allocating from
 * @len: length of whole packet - including PBC - in dwords
 * @cb: optional callback to call when the buffer is finished sending
 * @arg: argument for cb
 *
 * Return a pointer to a PIO buffer if successful, NULL if not enough room.
 */
struct pio_buf *sc_buffer_alloc(struct send_context *sc, u32 dw_len,
                                pio_release_cb cb, void *arg)
{
        struct pio_buf *pbuf = NULL;
        unsigned long flags;
        unsigned long avail;
        unsigned long blocks = dwords_to_blocks(dw_len);
        u32 fill_wrap;
        int trycount = 0;
        u32 head, next;

        spin_lock_irqsave(&sc->alloc_lock, flags);
        if (!(sc->flags & SCF_ENABLED)) {
                spin_unlock_irqrestore(&sc->alloc_lock, flags);
                goto done;
        }

retry:
        avail = (unsigned long)sc->credits - (sc->fill - sc->alloc_free);
        if (blocks > avail) {
                /* not enough room */
                if (unlikely(trycount)) { /* already tried to get more room */
                        spin_unlock_irqrestore(&sc->alloc_lock, flags);
                        goto done;
                }
                /* copy from receiver cache line and recalculate */
                sc->alloc_free = READ_ONCE(sc->free);
                avail =
                        (unsigned long)sc->credits -
                        (sc->fill - sc->alloc_free);
                if (blocks > avail) {
                        /* still no room, actively update */
                        sc_release_update(sc);
                        sc->alloc_free = READ_ONCE(sc->free);
                        trycount++;
                        goto retry;
                }
        }

        /* there is enough room */

        preempt_disable();
        this_cpu_inc(*sc->buffers_allocated);

        /* read this once */
        head = sc->sr_head;

        /* "allocate" the buffer */
        sc->fill += blocks;
        fill_wrap = sc->fill_wrap;
        sc->fill_wrap += blocks;
        if (sc->fill_wrap >= sc->credits)
                sc->fill_wrap = sc->fill_wrap - sc->credits;

        /*
         * Fill the parts that the releaser looks at before moving the head.
         * The only necessary piece is the sent_at field.  The credits
         * we have just allocated cannot have been returned yet, so the
         * cb and arg will not be looked at for a "while".  Put them
         * on this side of the memory barrier anyway.
         */
        pbuf = &sc->sr[head].pbuf;
        pbuf->sent_at = sc->fill;
        pbuf->cb = cb;
        pbuf->arg = arg;
        pbuf->sc = sc;  /* could be filled in at sc->sr init time */
        /* make sure this is in memory before updating the head */

        /* calculate next head index, do not store */
        next = head + 1;
        if (next >= sc->sr_size)
                next = 0;
        /*
         * update the head - must be last! - the releaser can look at fields
         * in pbuf once we move the head
         */
        smp_wmb();
        sc->sr_head = next;
        spin_unlock_irqrestore(&sc->alloc_lock, flags);

        /* finish filling in the buffer outside the lock */
        pbuf->start = sc->base_addr + fill_wrap * PIO_BLOCK_SIZE;
        pbuf->end = sc->base_addr + sc->size;
        pbuf->qw_written = 0;
        pbuf->carry_bytes = 0;
        pbuf->carry.val64 = 0;
done:
        return pbuf;
}

/*
 * There are at least two entities that can turn on credit return
 * interrupts and they can overlap.  Avoid problems by implementing
 * a count scheme that is enforced by a lock.  The lock is needed because
 * the count and CSR write must be paired.
 */

/*
 * Start credit return interrupts.  This is managed by a count.  If already
 * on, just increment the count.
 */
void sc_add_credit_return_intr(struct send_context *sc)
{
        unsigned long flags;

        /* lock must surround both the count change and the CSR update */
        spin_lock_irqsave(&sc->credit_ctrl_lock, flags);
        if (sc->credit_intr_count == 0) {
                sc->credit_ctrl |= SC(CREDIT_CTRL_CREDIT_INTR_SMASK);
                write_kctxt_csr(sc->dd, sc->hw_context,
                                SC(CREDIT_CTRL), sc->credit_ctrl);
        }
        sc->credit_intr_count++;
        spin_unlock_irqrestore(&sc->credit_ctrl_lock, flags);
}

/*
 * Stop credit return interrupts.  This is managed by a count.  Decrement the
 * count, if the last user, then turn the credit interrupts off.
 */
void sc_del_credit_return_intr(struct send_context *sc)
{
        unsigned long flags;

        WARN_ON(sc->credit_intr_count == 0);

        /* lock must surround both the count change and the CSR update */
        spin_lock_irqsave(&sc->credit_ctrl_lock, flags);
        sc->credit_intr_count--;
        if (sc->credit_intr_count == 0) {
                sc->credit_ctrl &= ~SC(CREDIT_CTRL_CREDIT_INTR_SMASK);
                write_kctxt_csr(sc->dd, sc->hw_context,
                                SC(CREDIT_CTRL), sc->credit_ctrl);
        }
        spin_unlock_irqrestore(&sc->credit_ctrl_lock, flags);
}

/*
 * The caller must be careful when calling this.  All needint calls
 * must be paired with !needint.
 */
void hfi1_sc_wantpiobuf_intr(struct send_context *sc, u32 needint)
{
        if (needint)
                sc_add_credit_return_intr(sc);
        else
                sc_del_credit_return_intr(sc);
        trace_hfi1_wantpiointr(sc, needint, sc->credit_ctrl);
        if (needint) {
                mmiowb();
                sc_return_credits(sc);
        }
}

/**
 * sc_piobufavail - callback when a PIO buffer is available
 * @sc: the send context
 *
 * This is called from the interrupt handler when a PIO buffer is
 * available after hfi1_verbs_send() returned an error that no buffers were
 * available. Disable the interrupt if there are no more QPs waiting.
 */
static void sc_piobufavail(struct send_context *sc)
{
        struct hfi1_devdata *dd = sc->dd;
        struct hfi1_ibdev *dev = &dd->verbs_dev;
        struct list_head *list;
        struct rvt_qp *qps[PIO_WAIT_BATCH_SIZE];
        struct rvt_qp *qp;
        struct hfi1_qp_priv *priv;
        unsigned long flags;
        uint i, n = 0, max_idx = 0;
        u8 max_starved_cnt = 0;

        if (dd->send_contexts[sc->sw_index].type != SC_KERNEL &&
            dd->send_contexts[sc->sw_index].type != SC_VL15)
                return;
        list = &sc->piowait;
        /*
         * Note: checking that the piowait list is empty and clearing
         * the buffer available interrupt needs to be atomic or we
         * could end up with QPs on the wait list with the interrupt
         * disabled.
         */
        write_seqlock_irqsave(&dev->iowait_lock, flags);
        while (!list_empty(list)) {
                struct iowait *wait;

                if (n == ARRAY_SIZE(qps))
                        break;
                wait = list_first_entry(list, struct iowait, list);
                qp = iowait_to_qp(wait);
                priv = qp->priv;
                list_del_init(&priv->s_iowait.list);
                priv->s_iowait.lock = NULL;
                iowait_starve_find_max(wait, &max_starved_cnt, n, &max_idx);
                /* refcount held until actual wake up */
                qps[n++] = qp;
        }
        /*
         * If there had been waiters and there are more
         * insure that we redo the force to avoid a potential hang.
         */
        if (n) {
                hfi1_sc_wantpiobuf_intr(sc, 0);
                if (!list_empty(list))
                        hfi1_sc_wantpiobuf_intr(sc, 1);
        }
        write_sequnlock_irqrestore(&dev->iowait_lock, flags);

        /* Wake up the most starved one first */
        if (n)
                hfi1_qp_wakeup(qps[max_idx],
                               RVT_S_WAIT_PIO | RVT_S_WAIT_PIO_DRAIN);
        for (i = 0; i < n; i++)
                if (i != max_idx)
                        hfi1_qp_wakeup(qps[i],
                                       RVT_S_WAIT_PIO | RVT_S_WAIT_PIO_DRAIN);
}

/* translate a send credit update to a bit code of reasons */
static inline int fill_code(u64 hw_free)
{
        int code = 0;

        if (hw_free & CR_STATUS_SMASK)
                code |= PRC_STATUS_ERR;
        if (hw_free & CR_CREDIT_RETURN_DUE_TO_PBC_SMASK)
                code |= PRC_PBC;
        if (hw_free & CR_CREDIT_RETURN_DUE_TO_THRESHOLD_SMASK)
                code |= PRC_THRESHOLD;
        if (hw_free & CR_CREDIT_RETURN_DUE_TO_ERR_SMASK)
                code |= PRC_FILL_ERR;
        if (hw_free & CR_CREDIT_RETURN_DUE_TO_FORCE_SMASK)
                code |= PRC_SC_DISABLE;
        return code;
}

/* use the jiffies compare to get the wrap right */
#define sent_before(a, b) time_before(a, b)     /* a < b */

/*
 * The send context buffer "releaser".
 */
void sc_release_update(struct send_context *sc)
{
        struct pio_buf *pbuf;
        u64 hw_free;
        u32 head, tail;
        unsigned long old_free;
        unsigned long free;
        unsigned long extra;
        unsigned long flags;
        int code;

        if (!sc)
                return;

        spin_lock_irqsave(&sc->release_lock, flags);
        /* update free */
        hw_free = le64_to_cpu(*sc->hw_free);            /* volatile read */
        old_free = sc->free;
        extra = (((hw_free & CR_COUNTER_SMASK) >> CR_COUNTER_SHIFT)
                        - (old_free & CR_COUNTER_MASK))
                                & CR_COUNTER_MASK;
        free = old_free + extra;
        trace_hfi1_piofree(sc, extra);

        /* call sent buffer callbacks */
        code = -1;                              /* code not yet set */
        head = READ_ONCE(sc->sr_head);  /* snapshot the head */
        tail = sc->sr_tail;
        while (head != tail) {
                pbuf = &sc->sr[tail].pbuf;

                if (sent_before(free, pbuf->sent_at)) {
                        /* not sent yet */
                        break;
                }
                if (pbuf->cb) {
                        if (code < 0) /* fill in code on first user */
                                code = fill_code(hw_free);
                        (*pbuf->cb)(pbuf->arg, code);
                }

                tail++;
                if (tail >= sc->sr_size)
                        tail = 0;
        }
        sc->sr_tail = tail;
        /* make sure tail is updated before free */
        smp_wmb();
        sc->free = free;
        spin_unlock_irqrestore(&sc->release_lock, flags);
        sc_piobufavail(sc);
}

/*
 * Send context group releaser.  Argument is the send context that caused
 * the interrupt.  Called from the send context interrupt handler.
 *
 * Call release on all contexts in the group.
 *
 * This routine takes the sc_lock without an irqsave because it is only
 * called from an interrupt handler.  Adjust if that changes.
 */
void sc_group_release_update(struct hfi1_devdata *dd, u32 hw_context)
{
        struct send_context *sc;
        u32 sw_index;
        u32 gc, gc_end;

        spin_lock(&dd->sc_lock);
        sw_index = dd->hw_to_sw[hw_context];
        if (unlikely(sw_index >= dd->num_send_contexts)) {
                dd_dev_err(dd, "%s: invalid hw (%u) to sw (%u) mapping\n",
                           __func__, hw_context, sw_index);
                goto done;
        }
        sc = dd->send_contexts[sw_index].sc;
        if (unlikely(!sc))
                goto done;

        gc = group_context(hw_context, sc->group);
        gc_end = gc + group_size(sc->group);
        for (; gc < gc_end; gc++) {
                sw_index = dd->hw_to_sw[gc];
                if (unlikely(sw_index >= dd->num_send_contexts)) {
                        dd_dev_err(dd,
                                   "%s: invalid hw (%u) to sw (%u) mapping\n",
                                   __func__, hw_context, sw_index);
                        continue;
                }
                sc_release_update(dd->send_contexts[sw_index].sc);
        }
done:
        spin_unlock(&dd->sc_lock);
}

/*
 * pio_select_send_context_vl() - select send context
 * @dd: devdata
 * @selector: a spreading factor
 * @vl: this vl
 *
 * This function returns a send context based on the selector and a vl.
 * The mapping fields are protected by RCU
 */
struct send_context *pio_select_send_context_vl(struct hfi1_devdata *dd,
                                                u32 selector, u8 vl)
{
        struct pio_vl_map *m;
        struct pio_map_elem *e;
        struct send_context *rval;

        /*
         * NOTE This should only happen if SC->VL changed after the initial
         * checks on the QP/AH
         * Default will return VL0's send context below
         */
        if (unlikely(vl >= num_vls)) {
                rval = NULL;
                goto done;
        }

        rcu_read_lock();
        m = rcu_dereference(dd->pio_map);
        if (unlikely(!m)) {
                rcu_read_unlock();
                return dd->vld[0].sc;
        }
        e = m->map[vl & m->mask];
        rval = e->ksc[selector & e->mask];
        rcu_read_unlock();

done:
        rval = !rval ? dd->vld[0].sc : rval;
        return rval;
}

/*
 * pio_select_send_context_sc() - select send context
 * @dd: devdata
 * @selector: a spreading factor
 * @sc5: the 5 bit sc
 *
 * This function returns an send context based on the selector and an sc
 */
struct send_context *pio_select_send_context_sc(struct hfi1_devdata *dd,
                                                u32 selector, u8 sc5)
{
        u8 vl = sc_to_vlt(dd, sc5);

        return pio_select_send_context_vl(dd, selector, vl);
}

/*
 * Free the indicated map struct
 */
static void pio_map_free(struct pio_vl_map *m)
{
        int i;

        for (i = 0; m && i < m->actual_vls; i++)
                kfree(m->map[i]);
        kfree(m);
}

/*
 * Handle RCU callback
 */
static void pio_map_rcu_callback(struct rcu_head *list)
{
        struct pio_vl_map *m = container_of(list, struct pio_vl_map, list);

        pio_map_free(m);
}

/*
 * Set credit return threshold for the kernel send context
 */
static void set_threshold(struct hfi1_devdata *dd, int scontext, int i)
{
        u32 thres;

        thres = min(sc_percent_to_threshold(dd->kernel_send_context[scontext],
                                            50),
                    sc_mtu_to_threshold(dd->kernel_send_context[scontext],
                                        dd->vld[i].mtu,
                                        dd->rcd[0]->rcvhdrqentsize));
        sc_set_cr_threshold(dd->kernel_send_context[scontext], thres);
}

/*
 * pio_map_init - called when #vls change
 * @dd: hfi1_devdata
 * @port: port number
 * @num_vls: number of vls
 * @vl_scontexts: per vl send context mapping (optional)
 *
 * This routine changes the mapping based on the number of vls.
 *
 * vl_scontexts is used to specify a non-uniform vl/send context
 * loading. NULL implies auto computing the loading and giving each
 * VL an uniform distribution of send contexts per VL.
 *
 * The auto algorithm computers the sc_per_vl and the number of extra
 * send contexts. Any extra send contexts are added from the last VL
 * on down
 *
 * rcu locking is used here to control access to the mapping fields.
 *
 * If either the num_vls or num_send_contexts are non-power of 2, the
 * array sizes in the struct pio_vl_map and the struct pio_map_elem are
 * rounded up to the next highest power of 2 and the first entry is
 * reused in a round robin fashion.
 *
 * If an error occurs the map change is not done and the mapping is not
 * chaged.
 *
 */
int pio_map_init(struct hfi1_devdata *dd, u8 port, u8 num_vls, u8 *vl_scontexts)
{
        int i, j;
        int extra, sc_per_vl;
        int scontext = 1;
        int num_kernel_send_contexts = 0;
        u8 lvl_scontexts[OPA_MAX_VLS];
        struct pio_vl_map *oldmap, *newmap;

        if (!vl_scontexts) {
                for (i = 0; i < dd->num_send_contexts; i++)
                        if (dd->send_contexts[i].type == SC_KERNEL)
                                num_kernel_send_contexts++;
                /* truncate divide */
                sc_per_vl = num_kernel_send_contexts / num_vls;
                /* extras */
                extra = num_kernel_send_contexts % num_vls;
                vl_scontexts = lvl_scontexts;
                /* add extras from last vl down */
                for (i = num_vls - 1; i >= 0; i--, extra--)
                        vl_scontexts[i] = sc_per_vl + (extra > 0 ? 1 : 0);
        }
        /* build new map */
        newmap = kzalloc(sizeof(*newmap) +
                         roundup_pow_of_two(num_vls) *
                         sizeof(struct pio_map_elem *),
                         GFP_KERNEL);
        if (!newmap)
                goto bail;
        newmap->actual_vls = num_vls;
        newmap->vls = roundup_pow_of_two(num_vls);
        newmap->mask = (1 << ilog2(newmap->vls)) - 1;
        for (i = 0; i < newmap->vls; i++) {
                /* save for wrap around */
                int first_scontext = scontext;

                if (i < newmap->actual_vls) {
                        int sz = roundup_pow_of_two(vl_scontexts[i]);

                        /* only allocate once */
                        newmap->map[i] = kzalloc(sizeof(*newmap->map[i]) +
                                                 sz * sizeof(struct
                                                             send_context *),
                                                 GFP_KERNEL);
                        if (!newmap->map[i])
                                goto bail;
                        newmap->map[i]->mask = (1 << ilog2(sz)) - 1;
                        /*
                         * assign send contexts and
                         * adjust credit return threshold
                         */
                        for (j = 0; j < sz; j++) {
                                if (dd->kernel_send_context[scontext]) {
                                        newmap->map[i]->ksc[j] =
                                        dd->kernel_send_context[scontext];
                                        set_threshold(dd, scontext, i);
                                }
                                if (++scontext >= first_scontext +
                                                  vl_scontexts[i])
                                        /* wrap back to first send context */
                                        scontext = first_scontext;
                        }
                } else {
                        /* just re-use entry without allocating */
                        newmap->map[i] = newmap->map[i % num_vls];
                }
                scontext = first_scontext + vl_scontexts[i];
        }
        /* newmap in hand, save old map */
        spin_lock_irq(&dd->pio_map_lock);
        oldmap = rcu_dereference_protected(dd->pio_map,
                                           lockdep_is_held(&dd->pio_map_lock));

        /* publish newmap */
        rcu_assign_pointer(dd->pio_map, newmap);

        spin_unlock_irq(&dd->pio_map_lock);
        /* success, free any old map after grace period */
        if (oldmap)
                call_rcu(&oldmap->list, pio_map_rcu_callback);
        return 0;
bail:
        /* free any partial allocation */
        pio_map_free(newmap);
        return -ENOMEM;
}

void free_pio_map(struct hfi1_devdata *dd)
{
        /* Free PIO map if allocated */
        if (rcu_access_pointer(dd->pio_map)) {
                spin_lock_irq(&dd->pio_map_lock);
                pio_map_free(rcu_access_pointer(dd->pio_map));
                RCU_INIT_POINTER(dd->pio_map, NULL);
                spin_unlock_irq(&dd->pio_map_lock);
                synchronize_rcu();
        }
        kfree(dd->kernel_send_context);
        dd->kernel_send_context = NULL;
}

int init_pervl_scs(struct hfi1_devdata *dd)
{
        int i;
        u64 mask, all_vl_mask = (u64)0x80ff; /* VLs 0-7, 15 */
        u64 data_vls_mask = (u64)0x00ff; /* VLs 0-7 */
        u32 ctxt;
        struct hfi1_pportdata *ppd = dd->pport;

        dd->vld[15].sc = sc_alloc(dd, SC_VL15,
                                  dd->rcd[0]->rcvhdrqentsize, dd->node);
        if (!dd->vld[15].sc)
                return -ENOMEM;

        hfi1_init_ctxt(dd->vld[15].sc);
        dd->vld[15].mtu = enum_to_mtu(OPA_MTU_2048);

        dd->kernel_send_context = kcalloc_node(dd->num_send_contexts,
                                               sizeof(struct send_context *),
                                               GFP_KERNEL, dd->node);
        if (!dd->kernel_send_context)
                goto freesc15;

        dd->kernel_send_context[0] = dd->vld[15].sc;

        for (i = 0; i < num_vls; i++) {
                /*
                 * Since this function does not deal with a specific
                 * receive context but we need the RcvHdrQ entry size,
                 * use the size from rcd[0]. It is guaranteed to be
                 * valid at this point and will remain the same for all
                 * receive contexts.
                 */
                dd->vld[i].sc = sc_alloc(dd, SC_KERNEL,
                                         dd->rcd[0]->rcvhdrqentsize, dd->node);
                if (!dd->vld[i].sc)
                        goto nomem;
                dd->kernel_send_context[i + 1] = dd->vld[i].sc;
                hfi1_init_ctxt(dd->vld[i].sc);
                /* non VL15 start with the max MTU */
                dd->vld[i].mtu = hfi1_max_mtu;
        }
        for (i = num_vls; i < INIT_SC_PER_VL * num_vls; i++) {
                dd->kernel_send_context[i + 1] =
                sc_alloc(dd, SC_KERNEL, dd->rcd[0]->rcvhdrqentsize, dd->node);
                if (!dd->kernel_send_context[i + 1])
                        goto nomem;
                hfi1_init_ctxt(dd->kernel_send_context[i + 1]);
        }

        sc_enable(dd->vld[15].sc);
        ctxt = dd->vld[15].sc->hw_context;
        mask = all_vl_mask & ~(1LL << 15);
        write_kctxt_csr(dd, ctxt, SC(CHECK_VL), mask);
        dd_dev_info(dd,
                    "Using send context %u(%u) for VL15\n",
                    dd->vld[15].sc->sw_index, ctxt);

        for (i = 0; i < num_vls; i++) {
                sc_enable(dd->vld[i].sc);
                ctxt = dd->vld[i].sc->hw_context;
                mask = all_vl_mask & ~(data_vls_mask);
                write_kctxt_csr(dd, ctxt, SC(CHECK_VL), mask);
        }
        for (i = num_vls; i < INIT_SC_PER_VL * num_vls; i++) {
                sc_enable(dd->kernel_send_context[i + 1]);
                ctxt = dd->kernel_send_context[i + 1]->hw_context;
                mask = all_vl_mask & ~(data_vls_mask);
                write_kctxt_csr(dd, ctxt, SC(CHECK_VL), mask);
        }

        if (pio_map_init(dd, ppd->port - 1, num_vls, NULL))
                goto nomem;
        return 0;

nomem:
        for (i = 0; i < num_vls; i++) {
                sc_free(dd->vld[i].sc);
                dd->vld[i].sc = NULL;
        }

        for (i = num_vls; i < INIT_SC_PER_VL * num_vls; i++)
                sc_free(dd->kernel_send_context[i + 1]);

        kfree(dd->kernel_send_context);
        dd->kernel_send_context = NULL;

freesc15:
        sc_free(dd->vld[15].sc);
        return -ENOMEM;
}

int init_credit_return(struct hfi1_devdata *dd)
{
        int ret;
        int i;

        dd->cr_base = kcalloc(
                node_affinity.num_possible_nodes,
                sizeof(struct credit_return_base),
                GFP_KERNEL);
        if (!dd->cr_base) {
                ret = -ENOMEM;
                goto done;
        }
        for_each_node_with_cpus(i) {
                int bytes = TXE_NUM_CONTEXTS * sizeof(struct credit_return);

                set_dev_node(&dd->pcidev->dev, i);
                dd->cr_base[i].va = dma_zalloc_coherent(
                                        &dd->pcidev->dev,
                                        bytes,
                                        &dd->cr_base[i].dma,
                                        GFP_KERNEL);
                if (!dd->cr_base[i].va) {
                        set_dev_node(&dd->pcidev->dev, dd->node);
                        dd_dev_err(dd,
                                   "Unable to allocate credit return DMA range for NUMA %d\n",
                                   i);
                        ret = -ENOMEM;
                        goto done;
                }
        }
        set_dev_node(&dd->pcidev->dev, dd->node);

        ret = 0;
done:
        return ret;
}

void free_credit_return(struct hfi1_devdata *dd)
{
        int i;

        if (!dd->cr_base)
                return;
        for (i = 0; i < node_affinity.num_possible_nodes; i++) {
                if (dd->cr_base[i].va) {
                        dma_free_coherent(&dd->pcidev->dev,
                                          TXE_NUM_CONTEXTS *
                                          sizeof(struct credit_return),
                                          dd->cr_base[i].va,
                                          dd->cr_base[i].dma);
                }
        }
        kfree(dd->cr_base);
        dd->cr_base = NULL;
}