treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / drivers / hwtracing / intel_th / msu.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Intel(R) Trace Hub Memory Storage Unit
 *
 * Copyright (C) 2014-2015 Intel Corporation.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/sizes.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/workqueue.h>
#include <linux/dma-mapping.h>

#ifdef CONFIG_X86
#include <asm/set_memory.h>
#endif

#include <linux/intel_th.h>
#include "intel_th.h"
#include "msu.h"

#define msc_dev(x) (&(x)->thdev->dev)

/*
 * Lockout state transitions:
 *   READY -> INUSE -+-> LOCKED -+-> READY -> etc.
 *                   \-----------/
 * WIN_READY:   window can be used by HW
 * WIN_INUSE:   window is in use
 * WIN_LOCKED:  window is filled up and is being processed by the buffer
 * handling code
 *
 * All state transitions happen automatically, except for the LOCKED->READY,
 * which needs to be signalled by the buffer code by calling
 * intel_th_msc_window_unlock().
 *
 * When the interrupt handler has to switch to the next window, it checks
 * whether it's READY, and if it is, it performs the switch and tracing
 * continues. If it's LOCKED, it stops the trace.
 */
enum lockout_state {
        WIN_READY = 0,
        WIN_INUSE,
        WIN_LOCKED
};

/**
 * struct msc_window - multiblock mode window descriptor
 * @entry:      window list linkage (msc::win_list)
 * @pgoff:      page offset into the buffer that this window starts at
 * @lockout:    lockout state, see comment below
 * @lo_lock:    lockout state serialization
 * @nr_blocks:  number of blocks (pages) in this window
 * @nr_segs:    number of segments in this window (<= @nr_blocks)
 * @_sgt:       array of block descriptors
 * @sgt:        array of block descriptors
 */
struct msc_window {
        struct list_head        entry;
        unsigned long           pgoff;
        enum lockout_state      lockout;
        spinlock_t              lo_lock;
        unsigned int            nr_blocks;
        unsigned int            nr_segs;
        struct msc              *msc;
        struct sg_table         _sgt;
        struct sg_table         *sgt;
};

/**
 * struct msc_iter - iterator for msc buffer
 * @entry:              msc::iter_list linkage
 * @msc:                pointer to the MSC device
 * @start_win:          oldest window
 * @win:                current window
 * @offset:             current logical offset into the buffer
 * @start_block:        oldest block in the window
 * @block:              block number in the window
 * @block_off:          offset into current block
 * @wrap_count:         block wrapping handling
 * @eof:                end of buffer reached
 */
struct msc_iter {
        struct list_head        entry;
        struct msc              *msc;
        struct msc_window       *start_win;
        struct msc_window       *win;
        unsigned long           offset;
        struct scatterlist      *start_block;
        struct scatterlist      *block;
        unsigned int            block_off;
        unsigned int            wrap_count;
        unsigned int            eof;
};

/**
 * struct msc - MSC device representation
 * @reg_base:           register window base address
 * @thdev:              intel_th_device pointer
 * @mbuf:               MSU buffer, if assigned
 * @mbuf_priv           MSU buffer's private data, if @mbuf
 * @win_list:           list of windows in multiblock mode
 * @single_sgt:         single mode buffer
 * @cur_win:            current window
 * @nr_pages:           total number of pages allocated for this buffer
 * @single_sz:          amount of data in single mode
 * @single_wrap:        single mode wrap occurred
 * @base:               buffer's base pointer
 * @base_addr:          buffer's base address
 * @user_count:         number of users of the buffer
 * @mmap_count:         number of mappings
 * @buf_mutex:          mutex to serialize access to buffer-related bits

 * @enabled:            MSC is enabled
 * @wrap:               wrapping is enabled
 * @mode:               MSC operating mode
 * @burst_len:          write burst length
 * @index:              number of this MSC in the MSU
 */
struct msc {
        void __iomem            *reg_base;
        void __iomem            *msu_base;
        struct intel_th_device  *thdev;

        const struct msu_buffer *mbuf;
        void                    *mbuf_priv;

        struct work_struct      work;
        struct list_head        win_list;
        struct sg_table         single_sgt;
        struct msc_window       *cur_win;
        unsigned long           nr_pages;
        unsigned long           single_sz;
        unsigned int            single_wrap : 1;
        void                    *base;
        dma_addr_t              base_addr;
        u32                     orig_addr;
        u32                     orig_sz;

        /* <0: no buffer, 0: no users, >0: active users */
        atomic_t                user_count;

        atomic_t                mmap_count;
        struct mutex            buf_mutex;

        struct list_head        iter_list;

        /* config */
        unsigned int            enabled : 1,
                                wrap    : 1,
                                do_irq  : 1;
        unsigned int            mode;
        unsigned int            burst_len;
        unsigned int            index;
};

static LIST_HEAD(msu_buffer_list);
static DEFINE_MUTEX(msu_buffer_mutex);

/**
 * struct msu_buffer_entry - internal MSU buffer bookkeeping
 * @entry:      link to msu_buffer_list
 * @mbuf:       MSU buffer object
 * @owner:      module that provides this MSU buffer
 */
struct msu_buffer_entry {
        struct list_head        entry;
        const struct msu_buffer *mbuf;
        struct module           *owner;
};

static struct msu_buffer_entry *__msu_buffer_entry_find(const char *name)
{
        struct msu_buffer_entry *mbe;

        lockdep_assert_held(&msu_buffer_mutex);

        list_for_each_entry(mbe, &msu_buffer_list, entry) {
                if (!strcmp(mbe->mbuf->name, name))
                        return mbe;
        }

        return NULL;
}

static const struct msu_buffer *
msu_buffer_get(const char *name)
{
        struct msu_buffer_entry *mbe;

        mutex_lock(&msu_buffer_mutex);
        mbe = __msu_buffer_entry_find(name);
        if (mbe && !try_module_get(mbe->owner))
                mbe = NULL;
        mutex_unlock(&msu_buffer_mutex);

        return mbe ? mbe->mbuf : NULL;
}

static void msu_buffer_put(const struct msu_buffer *mbuf)
{
        struct msu_buffer_entry *mbe;

        mutex_lock(&msu_buffer_mutex);
        mbe = __msu_buffer_entry_find(mbuf->name);
        if (mbe)
                module_put(mbe->owner);
        mutex_unlock(&msu_buffer_mutex);
}

int intel_th_msu_buffer_register(const struct msu_buffer *mbuf,
                                 struct module *owner)
{
        struct msu_buffer_entry *mbe;
        int ret = 0;

        mbe = kzalloc(sizeof(*mbe), GFP_KERNEL);
        if (!mbe)
                return -ENOMEM;

        mutex_lock(&msu_buffer_mutex);
        if (__msu_buffer_entry_find(mbuf->name)) {
                ret = -EEXIST;
                kfree(mbe);
                goto unlock;
        }

        mbe->mbuf = mbuf;
        mbe->owner = owner;
        list_add_tail(&mbe->entry, &msu_buffer_list);
unlock:
        mutex_unlock(&msu_buffer_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(intel_th_msu_buffer_register);

void intel_th_msu_buffer_unregister(const struct msu_buffer *mbuf)
{
        struct msu_buffer_entry *mbe;

        mutex_lock(&msu_buffer_mutex);
        mbe = __msu_buffer_entry_find(mbuf->name);
        if (mbe) {
                list_del(&mbe->entry);
                kfree(mbe);
        }
        mutex_unlock(&msu_buffer_mutex);
}
EXPORT_SYMBOL_GPL(intel_th_msu_buffer_unregister);

static inline bool msc_block_is_empty(struct msc_block_desc *bdesc)
{
        /* header hasn't been written */
        if (!bdesc->valid_dw)
                return true;

        /* valid_dw includes the header */
        if (!msc_data_sz(bdesc))
                return true;

        return false;
}

static inline struct scatterlist *msc_win_base_sg(struct msc_window *win)
{
        return win->sgt->sgl;
}

static inline struct msc_block_desc *msc_win_base(struct msc_window *win)
{
        return sg_virt(msc_win_base_sg(win));
}

static inline dma_addr_t msc_win_base_dma(struct msc_window *win)
{
        return sg_dma_address(msc_win_base_sg(win));
}

static inline unsigned long
msc_win_base_pfn(struct msc_window *win)
{
        return PFN_DOWN(msc_win_base_dma(win));
}

/**
 * msc_is_last_win() - check if a window is the last one for a given MSC
 * @win:        window
 * Return:      true if @win is the last window in MSC's multiblock buffer
 */
static inline bool msc_is_last_win(struct msc_window *win)
{
        return win->entry.next == &win->msc->win_list;
}

/**
 * msc_next_window() - return next window in the multiblock buffer
 * @win:        current window
 *
 * Return:      window following the current one
 */
static struct msc_window *msc_next_window(struct msc_window *win)
{
        if (msc_is_last_win(win))
                return list_first_entry(&win->msc->win_list, struct msc_window,
                                        entry);

        return list_next_entry(win, entry);
}

static size_t msc_win_total_sz(struct msc_window *win)
{
        struct scatterlist *sg;
        unsigned int blk;
        size_t size = 0;

        for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
                struct msc_block_desc *bdesc = sg_virt(sg);

                if (msc_block_wrapped(bdesc))
                        return (size_t)win->nr_blocks << PAGE_SHIFT;

                size += msc_total_sz(bdesc);
                if (msc_block_last_written(bdesc))
                        break;
        }

        return size;
}

/**
 * msc_find_window() - find a window matching a given sg_table
 * @msc:        MSC device
 * @sgt:        SG table of the window
 * @nonempty:   skip over empty windows
 *
 * Return:      MSC window structure pointer or NULL if the window
 *              could not be found.
 */
static struct msc_window *
msc_find_window(struct msc *msc, struct sg_table *sgt, bool nonempty)
{
        struct msc_window *win;
        unsigned int found = 0;

        if (list_empty(&msc->win_list))
                return NULL;

        /*
         * we might need a radix tree for this, depending on how
         * many windows a typical user would allocate; ideally it's
         * something like 2, in which case we're good
         */
        list_for_each_entry(win, &msc->win_list, entry) {
                if (win->sgt == sgt)
                        found++;

                /* skip the empty ones */
                if (nonempty && msc_block_is_empty(msc_win_base(win)))
                        continue;

                if (found)
                        return win;
        }

        return NULL;
}

/**
 * msc_oldest_window() - locate the window with oldest data
 * @msc:        MSC device
 *
 * This should only be used in multiblock mode. Caller should hold the
 * msc::user_count reference.
 *
 * Return:      the oldest window with valid data
 */
static struct msc_window *msc_oldest_window(struct msc *msc)
{
        struct msc_window *win;

        if (list_empty(&msc->win_list))
                return NULL;

        win = msc_find_window(msc, msc_next_window(msc->cur_win)->sgt, true);
        if (win)
                return win;

        return list_first_entry(&msc->win_list, struct msc_window, entry);
}

/**
 * msc_win_oldest_sg() - locate the oldest block in a given window
 * @win:        window to look at
 *
 * Return:      index of the block with the oldest data
 */
static struct scatterlist *msc_win_oldest_sg(struct msc_window *win)
{
        unsigned int blk;
        struct scatterlist *sg;
        struct msc_block_desc *bdesc = msc_win_base(win);

        /* without wrapping, first block is the oldest */
        if (!msc_block_wrapped(bdesc))
                return msc_win_base_sg(win);

        /*
         * with wrapping, last written block contains both the newest and the
         * oldest data for this window.
         */
        for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
                struct msc_block_desc *bdesc = sg_virt(sg);

                if (msc_block_last_written(bdesc))
                        return sg;
        }

        return msc_win_base_sg(win);
}

static struct msc_block_desc *msc_iter_bdesc(struct msc_iter *iter)
{
        return sg_virt(iter->block);
}

static struct msc_iter *msc_iter_install(struct msc *msc)
{
        struct msc_iter *iter;

        iter = kzalloc(sizeof(*iter), GFP_KERNEL);
        if (!iter)
                return ERR_PTR(-ENOMEM);

        mutex_lock(&msc->buf_mutex);

        /*
         * Reading and tracing are mutually exclusive; if msc is
         * enabled, open() will fail; otherwise existing readers
         * will prevent enabling the msc and the rest of fops don't
         * need to worry about it.
         */
        if (msc->enabled) {
                kfree(iter);
                iter = ERR_PTR(-EBUSY);
                goto unlock;
        }

        iter->msc = msc;

        list_add_tail(&iter->entry, &msc->iter_list);
unlock:
        mutex_unlock(&msc->buf_mutex);

        return iter;
}

static void msc_iter_remove(struct msc_iter *iter, struct msc *msc)
{
        mutex_lock(&msc->buf_mutex);
        list_del(&iter->entry);
        mutex_unlock(&msc->buf_mutex);

        kfree(iter);
}

static void msc_iter_block_start(struct msc_iter *iter)
{
        if (iter->start_block)
                return;

        iter->start_block = msc_win_oldest_sg(iter->win);
        iter->block = iter->start_block;
        iter->wrap_count = 0;

        /*
         * start with the block with oldest data; if data has wrapped
         * in this window, it should be in this block
         */
        if (msc_block_wrapped(msc_iter_bdesc(iter)))
                iter->wrap_count = 2;

}

static int msc_iter_win_start(struct msc_iter *iter, struct msc *msc)
{
        /* already started, nothing to do */
        if (iter->start_win)
                return 0;

        iter->start_win = msc_oldest_window(msc);
        if (!iter->start_win)
                return -EINVAL;

        iter->win = iter->start_win;
        iter->start_block = NULL;

        msc_iter_block_start(iter);

        return 0;
}

static int msc_iter_win_advance(struct msc_iter *iter)
{
        iter->win = msc_next_window(iter->win);
        iter->start_block = NULL;

        if (iter->win == iter->start_win) {
                iter->eof++;
                return 1;
        }

        msc_iter_block_start(iter);

        return 0;
}

static int msc_iter_block_advance(struct msc_iter *iter)
{
        iter->block_off = 0;

        /* wrapping */
        if (iter->wrap_count && iter->block == iter->start_block) {
                iter->wrap_count--;
                if (!iter->wrap_count)
                        /* copied newest data from the wrapped block */
                        return msc_iter_win_advance(iter);
        }

        /* no wrapping, check for last written block */
        if (!iter->wrap_count && msc_block_last_written(msc_iter_bdesc(iter)))
                /* copied newest data for the window */
                return msc_iter_win_advance(iter);

        /* block advance */
        if (sg_is_last(iter->block))
                iter->block = msc_win_base_sg(iter->win);
        else
                iter->block = sg_next(iter->block);

        /* no wrapping, sanity check in case there is no last written block */
        if (!iter->wrap_count && iter->block == iter->start_block)
                return msc_iter_win_advance(iter);

        return 0;
}

/**
 * msc_buffer_iterate() - go through multiblock buffer's data
 * @iter:       iterator structure
 * @size:       amount of data to scan
 * @data:       callback's private data
 * @fn:         iterator callback
 *
 * This will start at the window which will be written to next (containing
 * the oldest data) and work its way to the current window, calling @fn
 * for each chunk of data as it goes.
 *
 * Caller should have msc::user_count reference to make sure the buffer
 * doesn't disappear from under us.
 *
 * Return:      amount of data actually scanned.
 */
static ssize_t
msc_buffer_iterate(struct msc_iter *iter, size_t size, void *data,
                   unsigned long (*fn)(void *, void *, size_t))
{
        struct msc *msc = iter->msc;
        size_t len = size;
        unsigned int advance;

        if (iter->eof)
                return 0;

        /* start with the oldest window */
        if (msc_iter_win_start(iter, msc))
                return 0;

        do {
                unsigned long data_bytes = msc_data_sz(msc_iter_bdesc(iter));
                void *src = (void *)msc_iter_bdesc(iter) + MSC_BDESC;
                size_t tocopy = data_bytes, copied = 0;
                size_t remaining = 0;

                advance = 1;

                /*
                 * If block wrapping happened, we need to visit the last block
                 * twice, because it contains both the oldest and the newest
                 * data in this window.
                 *
                 * First time (wrap_count==2), in the very beginning, to collect
                 * the oldest data, which is in the range
                 * (data_bytes..DATA_IN_PAGE).
                 *
                 * Second time (wrap_count==1), it's just like any other block,
                 * containing data in the range of [MSC_BDESC..data_bytes].
                 */
                if (iter->block == iter->start_block && iter->wrap_count == 2) {
                        tocopy = DATA_IN_PAGE - data_bytes;
                        src += data_bytes;
                }

                if (!tocopy)
                        goto next_block;

                tocopy -= iter->block_off;
                src += iter->block_off;

                if (len < tocopy) {
                        tocopy = len;
                        advance = 0;
                }

                remaining = fn(data, src, tocopy);

                if (remaining)
                        advance = 0;

                copied = tocopy - remaining;
                len -= copied;
                iter->block_off += copied;
                iter->offset += copied;

                if (!advance)
                        break;

next_block:
                if (msc_iter_block_advance(iter))
                        break;

        } while (len);

        return size - len;
}

/**
 * msc_buffer_clear_hw_header() - clear hw header for multiblock
 * @msc:        MSC device
 */
static void msc_buffer_clear_hw_header(struct msc *msc)
{
        struct msc_window *win;
        struct scatterlist *sg;

        list_for_each_entry(win, &msc->win_list, entry) {
                unsigned int blk;
                size_t hw_sz = sizeof(struct msc_block_desc) -
                        offsetof(struct msc_block_desc, hw_tag);

                for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
                        struct msc_block_desc *bdesc = sg_virt(sg);

                        memset(&bdesc->hw_tag, 0, hw_sz);
                }
        }
}

static int intel_th_msu_init(struct msc *msc)
{
        u32 mintctl, msusts;

        if (!msc->do_irq)
                return 0;

        if (!msc->mbuf)
                return 0;

        mintctl = ioread32(msc->msu_base + REG_MSU_MINTCTL);
        mintctl |= msc->index ? M1BLIE : M0BLIE;
        iowrite32(mintctl, msc->msu_base + REG_MSU_MINTCTL);
        if (mintctl != ioread32(msc->msu_base + REG_MSU_MINTCTL)) {
                dev_info(msc_dev(msc), "MINTCTL ignores writes: no usable interrupts\n");
                msc->do_irq = 0;
                return 0;
        }

        msusts = ioread32(msc->msu_base + REG_MSU_MSUSTS);
        iowrite32(msusts, msc->msu_base + REG_MSU_MSUSTS);

        return 0;
}

static void intel_th_msu_deinit(struct msc *msc)
{
        u32 mintctl;

        if (!msc->do_irq)
                return;

        mintctl = ioread32(msc->msu_base + REG_MSU_MINTCTL);
        mintctl &= msc->index ? ~M1BLIE : ~M0BLIE;
        iowrite32(mintctl, msc->msu_base + REG_MSU_MINTCTL);
}

static int msc_win_set_lockout(struct msc_window *win,
                               enum lockout_state expect,
                               enum lockout_state new)
{
        enum lockout_state old;
        unsigned long flags;
        int ret = 0;

        if (!win->msc->mbuf)
                return 0;

        spin_lock_irqsave(&win->lo_lock, flags);
        old = win->lockout;

        if (old != expect) {
                ret = -EINVAL;
                dev_warn_ratelimited(msc_dev(win->msc),
                                     "expected lockout state %d, got %d\n",
                                     expect, old);
                goto unlock;
        }

        win->lockout = new;

        if (old == expect && new == WIN_LOCKED)
                atomic_inc(&win->msc->user_count);
        else if (old == expect && old == WIN_LOCKED)
                atomic_dec(&win->msc->user_count);

unlock:
        spin_unlock_irqrestore(&win->lo_lock, flags);

        if (ret) {
                if (expect == WIN_READY && old == WIN_LOCKED)
                        return -EBUSY;

                /* from intel_th_msc_window_unlock(), don't warn if not locked */
                if (expect == WIN_LOCKED && old == new)
                        return 0;
        }

        return ret;
}
/**
 * msc_configure() - set up MSC hardware
 * @msc:        the MSC device to configure
 *
 * Program storage mode, wrapping, burst length and trace buffer address
 * into a given MSC. Then, enable tracing and set msc::enabled.
 * The latter is serialized on msc::buf_mutex, so make sure to hold it.
 */
static int msc_configure(struct msc *msc)
{
        u32 reg;

        lockdep_assert_held(&msc->buf_mutex);

        if (msc->mode > MSC_MODE_MULTI)
                return -ENOTSUPP;

        if (msc->mode == MSC_MODE_MULTI) {
                if (msc_win_set_lockout(msc->cur_win, WIN_READY, WIN_INUSE))
                        return -EBUSY;

                msc_buffer_clear_hw_header(msc);
        }

        msc->orig_addr = ioread32(msc->reg_base + REG_MSU_MSC0BAR);
        msc->orig_sz   = ioread32(msc->reg_base + REG_MSU_MSC0SIZE);

        reg = msc->base_addr >> PAGE_SHIFT;
        iowrite32(reg, msc->reg_base + REG_MSU_MSC0BAR);

        if (msc->mode == MSC_MODE_SINGLE) {
                reg = msc->nr_pages;
                iowrite32(reg, msc->reg_base + REG_MSU_MSC0SIZE);
        }

        reg = ioread32(msc->reg_base + REG_MSU_MSC0CTL);
        reg &= ~(MSC_MODE | MSC_WRAPEN | MSC_EN | MSC_RD_HDR_OVRD);

        reg |= MSC_EN;
        reg |= msc->mode << __ffs(MSC_MODE);
        reg |= msc->burst_len << __ffs(MSC_LEN);

        if (msc->wrap)
                reg |= MSC_WRAPEN;

        iowrite32(reg, msc->reg_base + REG_MSU_MSC0CTL);

        intel_th_msu_init(msc);

        msc->thdev->output.multiblock = msc->mode == MSC_MODE_MULTI;
        intel_th_trace_enable(msc->thdev);
        msc->enabled = 1;

        if (msc->mbuf && msc->mbuf->activate)
                msc->mbuf->activate(msc->mbuf_priv);

        return 0;
}

/**
 * msc_disable() - disable MSC hardware
 * @msc:        MSC device to disable
 *
 * If @msc is enabled, disable tracing on the switch and then disable MSC
 * storage. Caller must hold msc::buf_mutex.
 */
static void msc_disable(struct msc *msc)
{
        struct msc_window *win = msc->cur_win;
        u32 reg;

        lockdep_assert_held(&msc->buf_mutex);

        if (msc->mode == MSC_MODE_MULTI)
                msc_win_set_lockout(win, WIN_INUSE, WIN_LOCKED);

        if (msc->mbuf && msc->mbuf->deactivate)
                msc->mbuf->deactivate(msc->mbuf_priv);
        intel_th_msu_deinit(msc);
        intel_th_trace_disable(msc->thdev);

        if (msc->mode == MSC_MODE_SINGLE) {
                reg = ioread32(msc->reg_base + REG_MSU_MSC0STS);
                msc->single_wrap = !!(reg & MSCSTS_WRAPSTAT);

                reg = ioread32(msc->reg_base + REG_MSU_MSC0MWP);
                msc->single_sz = reg & ((msc->nr_pages << PAGE_SHIFT) - 1);
                dev_dbg(msc_dev(msc), "MSCnMWP: %08x/%08lx, wrap: %d\n",
                        reg, msc->single_sz, msc->single_wrap);
        }

        reg = ioread32(msc->reg_base + REG_MSU_MSC0CTL);
        reg &= ~MSC_EN;
        iowrite32(reg, msc->reg_base + REG_MSU_MSC0CTL);

        if (msc->mbuf && msc->mbuf->ready)
                msc->mbuf->ready(msc->mbuf_priv, win->sgt,
                                 msc_win_total_sz(win));

        msc->enabled = 0;

        iowrite32(msc->orig_addr, msc->reg_base + REG_MSU_MSC0BAR);
        iowrite32(msc->orig_sz, msc->reg_base + REG_MSU_MSC0SIZE);

        dev_dbg(msc_dev(msc), "MSCnNWSA: %08x\n",
                ioread32(msc->reg_base + REG_MSU_MSC0NWSA));

        reg = ioread32(msc->reg_base + REG_MSU_MSC0STS);
        dev_dbg(msc_dev(msc), "MSCnSTS: %08x\n", reg);

        reg = ioread32(msc->reg_base + REG_MSU_MSUSTS);
        reg &= msc->index ? MSUSTS_MSC1BLAST : MSUSTS_MSC0BLAST;
        iowrite32(reg, msc->reg_base + REG_MSU_MSUSTS);
}

static int intel_th_msc_activate(struct intel_th_device *thdev)
{
        struct msc *msc = dev_get_drvdata(&thdev->dev);
        int ret = -EBUSY;

        if (!atomic_inc_unless_negative(&msc->user_count))
                return -ENODEV;

        mutex_lock(&msc->buf_mutex);

        /* if there are readers, refuse */
        if (list_empty(&msc->iter_list))
                ret = msc_configure(msc);

        mutex_unlock(&msc->buf_mutex);

        if (ret)
                atomic_dec(&msc->user_count);

        return ret;
}

static void intel_th_msc_deactivate(struct intel_th_device *thdev)
{
        struct msc *msc = dev_get_drvdata(&thdev->dev);

        mutex_lock(&msc->buf_mutex);
        if (msc->enabled) {
                msc_disable(msc);
                atomic_dec(&msc->user_count);
        }
        mutex_unlock(&msc->buf_mutex);
}

/**
 * msc_buffer_contig_alloc() - allocate a contiguous buffer for SINGLE mode
 * @msc:        MSC device
 * @size:       allocation size in bytes
 *
 * This modifies msc::base, which requires msc::buf_mutex to serialize, so the
 * caller is expected to hold it.
 *
 * Return:      0 on success, -errno otherwise.
 */
static int msc_buffer_contig_alloc(struct msc *msc, unsigned long size)
{
        unsigned long nr_pages = size >> PAGE_SHIFT;
        unsigned int order = get_order(size);
        struct page *page;
        int ret;

        if (!size)
                return 0;

        ret = sg_alloc_table(&msc->single_sgt, 1, GFP_KERNEL);
        if (ret)
                goto err_out;

        ret = -ENOMEM;
        page = alloc_pages(GFP_KERNEL | __GFP_ZERO | GFP_DMA32, order);
        if (!page)
                goto err_free_sgt;

        split_page(page, order);
        sg_set_buf(msc->single_sgt.sgl, page_address(page), size);

        ret = dma_map_sg(msc_dev(msc)->parent->parent, msc->single_sgt.sgl, 1,
                         DMA_FROM_DEVICE);
        if (ret < 0)
                goto err_free_pages;

        msc->nr_pages = nr_pages;
        msc->base = page_address(page);
        msc->base_addr = sg_dma_address(msc->single_sgt.sgl);

        return 0;

err_free_pages:
        __free_pages(page, order);

err_free_sgt:
        sg_free_table(&msc->single_sgt);

err_out:
        return ret;
}

/**
 * msc_buffer_contig_free() - free a contiguous buffer
 * @msc:        MSC configured in SINGLE mode
 */
static void msc_buffer_contig_free(struct msc *msc)
{
        unsigned long off;

        dma_unmap_sg(msc_dev(msc)->parent->parent, msc->single_sgt.sgl,
                     1, DMA_FROM_DEVICE);
        sg_free_table(&msc->single_sgt);

        for (off = 0; off < msc->nr_pages << PAGE_SHIFT; off += PAGE_SIZE) {
                struct page *page = virt_to_page(msc->base + off);

                page->mapping = NULL;
                __free_page(page);
        }

        msc->nr_pages = 0;
}

/**
 * msc_buffer_contig_get_page() - find a page at a given offset
 * @msc:        MSC configured in SINGLE mode
 * @pgoff:      page offset
 *
 * Return:      page, if @pgoff is within the range, NULL otherwise.
 */
static struct page *msc_buffer_contig_get_page(struct msc *msc,
                                               unsigned long pgoff)
{
        if (pgoff >= msc->nr_pages)
                return NULL;

        return virt_to_page(msc->base + (pgoff << PAGE_SHIFT));
}

static int __msc_buffer_win_alloc(struct msc_window *win,
                                  unsigned int nr_segs)
{
        struct scatterlist *sg_ptr;
        void *block;
        int i, ret;

        ret = sg_alloc_table(win->sgt, nr_segs, GFP_KERNEL);
        if (ret)
                return -ENOMEM;

        for_each_sg(win->sgt->sgl, sg_ptr, nr_segs, i) {
                block = dma_alloc_coherent(msc_dev(win->msc)->parent->parent,
                                          PAGE_SIZE, &sg_dma_address(sg_ptr),
                                          GFP_KERNEL);
                if (!block)
                        goto err_nomem;

                sg_set_buf(sg_ptr, block, PAGE_SIZE);
        }

        return nr_segs;

err_nomem:
        for_each_sg(win->sgt->sgl, sg_ptr, i, ret)
                dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
                                  sg_virt(sg_ptr), sg_dma_address(sg_ptr));

        sg_free_table(win->sgt);

        return -ENOMEM;
}

#ifdef CONFIG_X86
static void msc_buffer_set_uc(struct msc_window *win, unsigned int nr_segs)
{
        struct scatterlist *sg_ptr;
        int i;

        for_each_sg(win->sgt->sgl, sg_ptr, nr_segs, i) {
                /* Set the page as uncached */
                set_memory_uc((unsigned long)sg_virt(sg_ptr),
                              PFN_DOWN(sg_ptr->length));
        }
}

static void msc_buffer_set_wb(struct msc_window *win)
{
        struct scatterlist *sg_ptr;
        int i;

        for_each_sg(win->sgt->sgl, sg_ptr, win->nr_segs, i) {
                /* Reset the page to write-back */
                set_memory_wb((unsigned long)sg_virt(sg_ptr),
                              PFN_DOWN(sg_ptr->length));
        }
}
#else /* !X86 */
static inline void
msc_buffer_set_uc(struct msc_window *win, unsigned int nr_segs) {}
static inline void msc_buffer_set_wb(struct msc_window *win) {}
#endif /* CONFIG_X86 */

/**
 * msc_buffer_win_alloc() - alloc a window for a multiblock mode
 * @msc:        MSC device
 * @nr_blocks:  number of pages in this window
 *
 * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
 * to serialize, so the caller is expected to hold it.
 *
 * Return:      0 on success, -errno otherwise.
 */
static int msc_buffer_win_alloc(struct msc *msc, unsigned int nr_blocks)
{
        struct msc_window *win;
        int ret = -ENOMEM;

        if (!nr_blocks)
                return 0;

        win = kzalloc(sizeof(*win), GFP_KERNEL);
        if (!win)
                return -ENOMEM;

        win->msc = msc;
        win->sgt = &win->_sgt;
        win->lockout = WIN_READY;
        spin_lock_init(&win->lo_lock);

        if (!list_empty(&msc->win_list)) {
                struct msc_window *prev = list_last_entry(&msc->win_list,
                                                          struct msc_window,
                                                          entry);

                win->pgoff = prev->pgoff + prev->nr_blocks;
        }

        if (msc->mbuf && msc->mbuf->alloc_window)
                ret = msc->mbuf->alloc_window(msc->mbuf_priv, &win->sgt,
                                              nr_blocks << PAGE_SHIFT);
        else
                ret = __msc_buffer_win_alloc(win, nr_blocks);

        if (ret <= 0)
                goto err_nomem;

        msc_buffer_set_uc(win, ret);

        win->nr_segs = ret;
        win->nr_blocks = nr_blocks;

        if (list_empty(&msc->win_list)) {
                msc->base = msc_win_base(win);
                msc->base_addr = msc_win_base_dma(win);
                msc->cur_win = win;
        }

        list_add_tail(&win->entry, &msc->win_list);
        msc->nr_pages += nr_blocks;

        return 0;

err_nomem:
        kfree(win);

        return ret;
}

static void __msc_buffer_win_free(struct msc *msc, struct msc_window *win)
{
        struct scatterlist *sg;
        int i;

        for_each_sg(win->sgt->sgl, sg, win->nr_segs, i) {
                struct page *page = sg_page(sg);

                page->mapping = NULL;
                dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
                                  sg_virt(sg), sg_dma_address(sg));
        }
        sg_free_table(win->sgt);
}

/**
 * msc_buffer_win_free() - free a window from MSC's window list
 * @msc:        MSC device
 * @win:        window to free
 *
 * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
 * to serialize, so the caller is expected to hold it.
 */
static void msc_buffer_win_free(struct msc *msc, struct msc_window *win)
{
        msc->nr_pages -= win->nr_blocks;

        list_del(&win->entry);
        if (list_empty(&msc->win_list)) {
                msc->base = NULL;
                msc->base_addr = 0;
        }

        msc_buffer_set_wb(win);

        if (msc->mbuf && msc->mbuf->free_window)
                msc->mbuf->free_window(msc->mbuf_priv, win->sgt);
        else
                __msc_buffer_win_free(msc, win);

        kfree(win);
}

/**
 * msc_buffer_relink() - set up block descriptors for multiblock mode
 * @msc:        MSC device
 *
 * This traverses msc::win_list, which requires msc::buf_mutex to serialize,
 * so the caller is expected to hold it.
 */
static void msc_buffer_relink(struct msc *msc)
{
        struct msc_window *win, *next_win;

        /* call with msc::mutex locked */
        list_for_each_entry(win, &msc->win_list, entry) {
                struct scatterlist *sg;
                unsigned int blk;
                u32 sw_tag = 0;

                /*
                 * Last window's next_win should point to the first window
                 * and MSC_SW_TAG_LASTWIN should be set.
                 */
                if (msc_is_last_win(win)) {
                        sw_tag |= MSC_SW_TAG_LASTWIN;
                        next_win = list_first_entry(&msc->win_list,
                                                    struct msc_window, entry);
                } else {
                        next_win = list_next_entry(win, entry);
                }

                for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
                        struct msc_block_desc *bdesc = sg_virt(sg);

                        memset(bdesc, 0, sizeof(*bdesc));

                        bdesc->next_win = msc_win_base_pfn(next_win);

                        /*
                         * Similarly to last window, last block should point
                         * to the first one.
                         */
                        if (blk == win->nr_segs - 1) {
                                sw_tag |= MSC_SW_TAG_LASTBLK;
                                bdesc->next_blk = msc_win_base_pfn(win);
                        } else {
                                dma_addr_t addr = sg_dma_address(sg_next(sg));

                                bdesc->next_blk = PFN_DOWN(addr);
                        }

                        bdesc->sw_tag = sw_tag;
                        bdesc->block_sz = sg->length / 64;
                }
        }

        /*
         * Make the above writes globally visible before tracing is
         * enabled to make sure hardware sees them coherently.
         */
        wmb();
}

static void msc_buffer_multi_free(struct msc *msc)
{
        struct msc_window *win, *iter;

        list_for_each_entry_safe(win, iter, &msc->win_list, entry)
                msc_buffer_win_free(msc, win);
}

static int msc_buffer_multi_alloc(struct msc *msc, unsigned long *nr_pages,
                                  unsigned int nr_wins)
{
        int ret, i;

        for (i = 0; i < nr_wins; i++) {
                ret = msc_buffer_win_alloc(msc, nr_pages[i]);
                if (ret) {
                        msc_buffer_multi_free(msc);
                        return ret;
                }
        }

        msc_buffer_relink(msc);

        return 0;
}

/**
 * msc_buffer_free() - free buffers for MSC
 * @msc:        MSC device
 *
 * Free MSC's storage buffers.
 *
 * This modifies msc::win_list and msc::base, which requires msc::buf_mutex to
 * serialize, so the caller is expected to hold it.
 */
static void msc_buffer_free(struct msc *msc)
{
        if (msc->mode == MSC_MODE_SINGLE)
                msc_buffer_contig_free(msc);
        else if (msc->mode == MSC_MODE_MULTI)
                msc_buffer_multi_free(msc);
}

/**
 * msc_buffer_alloc() - allocate a buffer for MSC
 * @msc:        MSC device
 * @size:       allocation size in bytes
 *
 * Allocate a storage buffer for MSC, depending on the msc::mode, it will be
 * either done via msc_buffer_contig_alloc() for SINGLE operation mode or
 * msc_buffer_win_alloc() for multiblock operation. The latter allocates one
 * window per invocation, so in multiblock mode this can be called multiple
 * times for the same MSC to allocate multiple windows.
 *
 * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
 * to serialize, so the caller is expected to hold it.
 *
 * Return:      0 on success, -errno otherwise.
 */
static int msc_buffer_alloc(struct msc *msc, unsigned long *nr_pages,
                            unsigned int nr_wins)
{
        int ret;

        /* -1: buffer not allocated */
        if (atomic_read(&msc->user_count) != -1)
                return -EBUSY;

        if (msc->mode == MSC_MODE_SINGLE) {
                if (nr_wins != 1)
                        return -EINVAL;

                ret = msc_buffer_contig_alloc(msc, nr_pages[0] << PAGE_SHIFT);
        } else if (msc->mode == MSC_MODE_MULTI) {
                ret = msc_buffer_multi_alloc(msc, nr_pages, nr_wins);
        } else {
                ret = -ENOTSUPP;
        }

        if (!ret) {
                /* allocation should be visible before the counter goes to 0 */
                smp_mb__before_atomic();

                if (WARN_ON_ONCE(atomic_cmpxchg(&msc->user_count, -1, 0) != -1))
                        return -EINVAL;
        }

        return ret;
}

/**
 * msc_buffer_unlocked_free_unless_used() - free a buffer unless it's in use
 * @msc:        MSC device
 *
 * This will free MSC buffer unless it is in use or there is no allocated
 * buffer.
 * Caller needs to hold msc::buf_mutex.
 *
 * Return:      0 on successful deallocation or if there was no buffer to
 *              deallocate, -EBUSY if there are active users.
 */
static int msc_buffer_unlocked_free_unless_used(struct msc *msc)
{
        int count, ret = 0;

        count = atomic_cmpxchg(&msc->user_count, 0, -1);

        /* > 0: buffer is allocated and has users */
        if (count > 0)
                ret = -EBUSY;
        /* 0: buffer is allocated, no users */
        else if (!count)
                msc_buffer_free(msc);
        /* < 0: no buffer, nothing to do */

        return ret;
}

/**
 * msc_buffer_free_unless_used() - free a buffer unless it's in use
 * @msc:        MSC device
 *
 * This is a locked version of msc_buffer_unlocked_free_unless_used().
 */
static int msc_buffer_free_unless_used(struct msc *msc)
{
        int ret;

        mutex_lock(&msc->buf_mutex);
        ret = msc_buffer_unlocked_free_unless_used(msc);
        mutex_unlock(&msc->buf_mutex);

        return ret;
}

/**
 * msc_buffer_get_page() - get MSC buffer page at a given offset
 * @msc:        MSC device
 * @pgoff:      page offset into the storage buffer
 *
 * This traverses msc::win_list, so holding msc::buf_mutex is expected from
 * the caller.
 *
 * Return:      page if @pgoff corresponds to a valid buffer page or NULL.
 */
static struct page *msc_buffer_get_page(struct msc *msc, unsigned long pgoff)
{
        struct msc_window *win;
        struct scatterlist *sg;
        unsigned int blk;

        if (msc->mode == MSC_MODE_SINGLE)
                return msc_buffer_contig_get_page(msc, pgoff);

        list_for_each_entry(win, &msc->win_list, entry)
                if (pgoff >= win->pgoff && pgoff < win->pgoff + win->nr_blocks)
                        goto found;

        return NULL;

found:
        pgoff -= win->pgoff;

        for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
                struct page *page = sg_page(sg);
                size_t pgsz = PFN_DOWN(sg->length);

                if (pgoff < pgsz)
                        return page + pgoff;

                pgoff -= pgsz;
        }

        return NULL;
}

/**
 * struct msc_win_to_user_struct - data for copy_to_user() callback
 * @buf:        userspace buffer to copy data to
 * @offset:     running offset
 */
struct msc_win_to_user_struct {
        char __user     *buf;
        unsigned long   offset;
};

/**
 * msc_win_to_user() - iterator for msc_buffer_iterate() to copy data to user
 * @data:       callback's private data
 * @src:        source buffer
 * @len:        amount of data to copy from the source buffer
 */
static unsigned long msc_win_to_user(void *data, void *src, size_t len)
{
        struct msc_win_to_user_struct *u = data;
        unsigned long ret;

        ret = copy_to_user(u->buf + u->offset, src, len);
        u->offset += len - ret;

        return ret;
}


/*
 * file operations' callbacks
 */

static int intel_th_msc_open(struct inode *inode, struct file *file)
{
        struct intel_th_device *thdev = file->private_data;
        struct msc *msc = dev_get_drvdata(&thdev->dev);
        struct msc_iter *iter;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        iter = msc_iter_install(msc);
        if (IS_ERR(iter))
                return PTR_ERR(iter);

        file->private_data = iter;

        return nonseekable_open(inode, file);
}

static int intel_th_msc_release(struct inode *inode, struct file *file)
{
        struct msc_iter *iter = file->private_data;
        struct msc *msc = iter->msc;

        msc_iter_remove(iter, msc);

        return 0;
}

static ssize_t
msc_single_to_user(struct msc *msc, char __user *buf, loff_t off, size_t len)
{
        unsigned long size = msc->nr_pages << PAGE_SHIFT, rem = len;
        unsigned long start = off, tocopy = 0;

        if (msc->single_wrap) {
                start += msc->single_sz;
                if (start < size) {
                        tocopy = min(rem, size - start);
                        if (copy_to_user(buf, msc->base + start, tocopy))
                                return -EFAULT;

                        buf += tocopy;
                        rem -= tocopy;
                        start += tocopy;
                }

                start &= size - 1;
                if (rem) {
                        tocopy = min(rem, msc->single_sz - start);
                        if (copy_to_user(buf, msc->base + start, tocopy))
                                return -EFAULT;

                        rem -= tocopy;
                }

                return len - rem;
        }

        if (copy_to_user(buf, msc->base + start, rem))
                return -EFAULT;

        return len;
}

static ssize_t intel_th_msc_read(struct file *file, char __user *buf,
                                 size_t len, loff_t *ppos)
{
        struct msc_iter *iter = file->private_data;
        struct msc *msc = iter->msc;
        size_t size;
        loff_t off = *ppos;
        ssize_t ret = 0;

        if (!atomic_inc_unless_negative(&msc->user_count))
                return 0;

        if (msc->mode == MSC_MODE_SINGLE && !msc->single_wrap)
                size = msc->single_sz;
        else
                size = msc->nr_pages << PAGE_SHIFT;

        if (!size)
                goto put_count;

        if (off >= size)
                goto put_count;

        if (off + len >= size)
                len = size - off;

        if (msc->mode == MSC_MODE_SINGLE) {
                ret = msc_single_to_user(msc, buf, off, len);
                if (ret >= 0)
                        *ppos += ret;
        } else if (msc->mode == MSC_MODE_MULTI) {
                struct msc_win_to_user_struct u = {
                        .buf    = buf,
                        .offset = 0,
                };

                ret = msc_buffer_iterate(iter, len, &u, msc_win_to_user);
                if (ret >= 0)
                        *ppos = iter->offset;
        } else {
                ret = -ENOTSUPP;
        }

put_count:
        atomic_dec(&msc->user_count);

        return ret;
}

/*
 * vm operations callbacks (vm_ops)
 */

static void msc_mmap_open(struct vm_area_struct *vma)
{
        struct msc_iter *iter = vma->vm_file->private_data;
        struct msc *msc = iter->msc;

        atomic_inc(&msc->mmap_count);
}

static void msc_mmap_close(struct vm_area_struct *vma)
{
        struct msc_iter *iter = vma->vm_file->private_data;
        struct msc *msc = iter->msc;
        unsigned long pg;

        if (!atomic_dec_and_mutex_lock(&msc->mmap_count, &msc->buf_mutex))
                return;

        /* drop page _refcounts */
        for (pg = 0; pg < msc->nr_pages; pg++) {
                struct page *page = msc_buffer_get_page(msc, pg);

                if (WARN_ON_ONCE(!page))
                        continue;

                if (page->mapping)
                        page->mapping = NULL;
        }

        /* last mapping -- drop user_count */
        atomic_dec(&msc->user_count);
        mutex_unlock(&msc->buf_mutex);
}

static vm_fault_t msc_mmap_fault(struct vm_fault *vmf)
{
        struct msc_iter *iter = vmf->vma->vm_file->private_data;
        struct msc *msc = iter->msc;

        vmf->page = msc_buffer_get_page(msc, vmf->pgoff);
        if (!vmf->page)
                return VM_FAULT_SIGBUS;

        get_page(vmf->page);
        vmf->page->mapping = vmf->vma->vm_file->f_mapping;
        vmf->page->index = vmf->pgoff;

        return 0;
}

static const struct vm_operations_struct msc_mmap_ops = {
        .open   = msc_mmap_open,
        .close  = msc_mmap_close,
        .fault  = msc_mmap_fault,
};

static int intel_th_msc_mmap(struct file *file, struct vm_area_struct *vma)
{
        unsigned long size = vma->vm_end - vma->vm_start;
        struct msc_iter *iter = vma->vm_file->private_data;
        struct msc *msc = iter->msc;
        int ret = -EINVAL;

        if (!size || offset_in_page(size))
                return -EINVAL;

        if (vma->vm_pgoff)
                return -EINVAL;

        /* grab user_count once per mmap; drop in msc_mmap_close() */
        if (!atomic_inc_unless_negative(&msc->user_count))
                return -EINVAL;

        if (msc->mode != MSC_MODE_SINGLE &&
            msc->mode != MSC_MODE_MULTI)
                goto out;

        if (size >> PAGE_SHIFT != msc->nr_pages)
                goto out;

        atomic_set(&msc->mmap_count, 1);
        ret = 0;

out:
        if (ret)
                atomic_dec(&msc->user_count);

        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
        vma->vm_flags |= VM_DONTEXPAND | VM_DONTCOPY;
        vma->vm_ops = &msc_mmap_ops;
        return ret;
}

static const struct file_operations intel_th_msc_fops = {
        .open           = intel_th_msc_open,
        .release        = intel_th_msc_release,
        .read           = intel_th_msc_read,
        .mmap           = intel_th_msc_mmap,
        .llseek         = no_llseek,
        .owner          = THIS_MODULE,
};

static void intel_th_msc_wait_empty(struct intel_th_device *thdev)
{
        struct msc *msc = dev_get_drvdata(&thdev->dev);
        unsigned long count;
        u32 reg;

        for (reg = 0, count = MSC_PLE_WAITLOOP_DEPTH;
             count && !(reg & MSCSTS_PLE); count--) {
                reg = __raw_readl(msc->reg_base + REG_MSU_MSC0STS);
                cpu_relax();
        }

        if (!count)
                dev_dbg(msc_dev(msc), "timeout waiting for MSC0 PLE\n");
}

static int intel_th_msc_init(struct msc *msc)
{
        atomic_set(&msc->user_count, -1);

        msc->mode = MSC_MODE_MULTI;
        mutex_init(&msc->buf_mutex);
        INIT_LIST_HEAD(&msc->win_list);
        INIT_LIST_HEAD(&msc->iter_list);

        msc->burst_len =
                (ioread32(msc->reg_base + REG_MSU_MSC0CTL) & MSC_LEN) >>
                __ffs(MSC_LEN);

        return 0;
}

static int msc_win_switch(struct msc *msc)
{
        struct msc_window *first;

        if (list_empty(&msc->win_list))
                return -EINVAL;

        first = list_first_entry(&msc->win_list, struct msc_window, entry);

        if (msc_is_last_win(msc->cur_win))
                msc->cur_win = first;
        else
                msc->cur_win = list_next_entry(msc->cur_win, entry);

        msc->base = msc_win_base(msc->cur_win);
        msc->base_addr = msc_win_base_dma(msc->cur_win);

        intel_th_trace_switch(msc->thdev);

        return 0;
}

/**
 * intel_th_msc_window_unlock - put the window back in rotation
 * @dev:        MSC device to which this relates
 * @sgt:        buffer's sg_table for the window, does nothing if NULL
 */
void intel_th_msc_window_unlock(struct device *dev, struct sg_table *sgt)
{
        struct msc *msc = dev_get_drvdata(dev);
        struct msc_window *win;

        if (!sgt)
                return;

        win = msc_find_window(msc, sgt, false);
        if (!win)
                return;

        msc_win_set_lockout(win, WIN_LOCKED, WIN_READY);
}
EXPORT_SYMBOL_GPL(intel_th_msc_window_unlock);

static void msc_work(struct work_struct *work)
{
        struct msc *msc = container_of(work, struct msc, work);

        intel_th_msc_deactivate(msc->thdev);
}

static irqreturn_t intel_th_msc_interrupt(struct intel_th_device *thdev)
{
        struct msc *msc = dev_get_drvdata(&thdev->dev);
        u32 msusts = ioread32(msc->msu_base + REG_MSU_MSUSTS);
        u32 mask = msc->index ? MSUSTS_MSC1BLAST : MSUSTS_MSC0BLAST;
        struct msc_window *win, *next_win;

        if (!msc->do_irq || !msc->mbuf)
                return IRQ_NONE;

        msusts &= mask;

        if (!msusts)
                return msc->enabled ? IRQ_HANDLED : IRQ_NONE;

        iowrite32(msusts, msc->msu_base + REG_MSU_MSUSTS);

        if (!msc->enabled)
                return IRQ_NONE;

        /* grab the window before we do the switch */
        win = msc->cur_win;
        if (!win)
                return IRQ_HANDLED;
        next_win = msc_next_window(win);
        if (!next_win)
                return IRQ_HANDLED;

        /* next window: if READY, proceed, if LOCKED, stop the trace */
        if (msc_win_set_lockout(next_win, WIN_READY, WIN_INUSE)) {
                schedule_work(&msc->work);
                return IRQ_HANDLED;
        }

        /* current window: INUSE -> LOCKED */
        msc_win_set_lockout(win, WIN_INUSE, WIN_LOCKED);

        msc_win_switch(msc);

        if (msc->mbuf && msc->mbuf->ready)
                msc->mbuf->ready(msc->mbuf_priv, win->sgt,
                                 msc_win_total_sz(win));

        return IRQ_HANDLED;
}

static const char * const msc_mode[] = {
        [MSC_MODE_SINGLE]       = "single",
        [MSC_MODE_MULTI]        = "multi",
        [MSC_MODE_EXI]          = "ExI",
        [MSC_MODE_DEBUG]        = "debug",
};

static ssize_t
wrap_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct msc *msc = dev_get_drvdata(dev);

        return scnprintf(buf, PAGE_SIZE, "%d\n", msc->wrap);
}

static ssize_t
wrap_store(struct device *dev, struct device_attribute *attr, const char *buf,
           size_t size)
{
        struct msc *msc = dev_get_drvdata(dev);
        unsigned long val;
        int ret;

        ret = kstrtoul(buf, 10, &val);
        if (ret)
                return ret;

        msc->wrap = !!val;

        return size;
}

static DEVICE_ATTR_RW(wrap);

static void msc_buffer_unassign(struct msc *msc)
{
        lockdep_assert_held(&msc->buf_mutex);

        if (!msc->mbuf)
                return;

        msc->mbuf->unassign(msc->mbuf_priv);
        msu_buffer_put(msc->mbuf);
        msc->mbuf_priv = NULL;
        msc->mbuf = NULL;
}

static ssize_t
mode_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct msc *msc = dev_get_drvdata(dev);
        const char *mode = msc_mode[msc->mode];
        ssize_t ret;

        mutex_lock(&msc->buf_mutex);
        if (msc->mbuf)
                mode = msc->mbuf->name;
        ret = scnprintf(buf, PAGE_SIZE, "%s\n", mode);
        mutex_unlock(&msc->buf_mutex);

        return ret;
}

static ssize_t
mode_store(struct device *dev, struct device_attribute *attr, const char *buf,
           size_t size)
{
        const struct msu_buffer *mbuf = NULL;
        struct msc *msc = dev_get_drvdata(dev);
        size_t len = size;
        char *cp, *mode;
        int i, ret;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        cp = memchr(buf, '\n', len);
        if (cp)
                len = cp - buf;

        mode = kstrndup(buf, len, GFP_KERNEL);
        if (!mode)
                return -ENOMEM;

        i = match_string(msc_mode, ARRAY_SIZE(msc_mode), mode);
        if (i >= 0) {
                kfree(mode);
                goto found;
        }

        /* Buffer sinks only work with a usable IRQ */
        if (!msc->do_irq) {
                kfree(mode);
                return -EINVAL;
        }

        mbuf = msu_buffer_get(mode);
        kfree(mode);
        if (mbuf)
                goto found;

        return -EINVAL;

found:
        mutex_lock(&msc->buf_mutex);
        ret = 0;

        /* Same buffer: do nothing */
        if (mbuf && mbuf == msc->mbuf) {
                /* put the extra reference we just got */
                msu_buffer_put(mbuf);
                goto unlock;
        }

        ret = msc_buffer_unlocked_free_unless_used(msc);
        if (ret)
                goto unlock;

        if (mbuf) {
                void *mbuf_priv = mbuf->assign(dev, &i);

                if (!mbuf_priv) {
                        ret = -ENOMEM;
                        goto unlock;
                }

                msc_buffer_unassign(msc);
                msc->mbuf_priv = mbuf_priv;
                msc->mbuf = mbuf;
        } else {
                msc_buffer_unassign(msc);
        }

        msc->mode = i;

unlock:
        if (ret && mbuf)
                msu_buffer_put(mbuf);
        mutex_unlock(&msc->buf_mutex);

        return ret ? ret : size;
}

static DEVICE_ATTR_RW(mode);

static ssize_t
nr_pages_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct msc *msc = dev_get_drvdata(dev);
        struct msc_window *win;
        size_t count = 0;

        mutex_lock(&msc->buf_mutex);

        if (msc->mode == MSC_MODE_SINGLE)
                count = scnprintf(buf, PAGE_SIZE, "%ld\n", msc->nr_pages);
        else if (msc->mode == MSC_MODE_MULTI) {
                list_for_each_entry(win, &msc->win_list, entry) {
                        count += scnprintf(buf + count, PAGE_SIZE - count,
                                           "%d%c", win->nr_blocks,
                                           msc_is_last_win(win) ? '\n' : ',');
                }
        } else {
                count = scnprintf(buf, PAGE_SIZE, "unsupported\n");
        }

        mutex_unlock(&msc->buf_mutex);

        return count;
}

static ssize_t
nr_pages_store(struct device *dev, struct device_attribute *attr,
               const char *buf, size_t size)
{
        struct msc *msc = dev_get_drvdata(dev);
        unsigned long val, *win = NULL, *rewin;
        size_t len = size;
        const char *p = buf;
        char *end, *s;
        int ret, nr_wins = 0;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        ret = msc_buffer_free_unless_used(msc);
        if (ret)
                return ret;

        /* scan the comma-separated list of allocation sizes */
        end = memchr(buf, '\n', len);
        if (end)
                len = end - buf;

        do {
                end = memchr(p, ',', len);
                s = kstrndup(p, end ? end - p : len, GFP_KERNEL);
                if (!s) {
                        ret = -ENOMEM;
                        goto free_win;
                }

                ret = kstrtoul(s, 10, &val);
                kfree(s);

                if (ret || !val)
                        goto free_win;

                if (nr_wins && msc->mode == MSC_MODE_SINGLE) {
                        ret = -EINVAL;
                        goto free_win;
                }

                nr_wins++;
                rewin = krealloc(win, sizeof(*win) * nr_wins, GFP_KERNEL);
                if (!rewin) {
                        kfree(win);
                        return -ENOMEM;
                }

                win = rewin;
                win[nr_wins - 1] = val;

                if (!end)
                        break;

                /* consume the number and the following comma, hence +1 */
                len -= end - p + 1;
                p = end + 1;
        } while (len);

        mutex_lock(&msc->buf_mutex);
        ret = msc_buffer_alloc(msc, win, nr_wins);
        mutex_unlock(&msc->buf_mutex);

free_win:
        kfree(win);

        return ret ? ret : size;
}

static DEVICE_ATTR_RW(nr_pages);

static ssize_t
win_switch_store(struct device *dev, struct device_attribute *attr,
                 const char *buf, size_t size)
{
        struct msc *msc = dev_get_drvdata(dev);
        unsigned long val;
        int ret;

        ret = kstrtoul(buf, 10, &val);
        if (ret)
                return ret;

        if (val != 1)
                return -EINVAL;

        ret = -EINVAL;
        mutex_lock(&msc->buf_mutex);
        /*
         * Window switch can only happen in the "multi" mode.
         * If a external buffer is engaged, they have the full
         * control over window switching.
         */
        if (msc->mode == MSC_MODE_MULTI && !msc->mbuf)
                ret = msc_win_switch(msc);
        mutex_unlock(&msc->buf_mutex);

        return ret ? ret : size;
}

static DEVICE_ATTR_WO(win_switch);

static struct attribute *msc_output_attrs[] = {
        &dev_attr_wrap.attr,
        &dev_attr_mode.attr,
        &dev_attr_nr_pages.attr,
        &dev_attr_win_switch.attr,
        NULL,
};

static struct attribute_group msc_output_group = {
        .attrs  = msc_output_attrs,
};

static int intel_th_msc_probe(struct intel_th_device *thdev)
{
        struct device *dev = &thdev->dev;
        struct resource *res;
        struct msc *msc;
        void __iomem *base;
        int err;

        res = intel_th_device_get_resource(thdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

        base = devm_ioremap(dev, res->start, resource_size(res));
        if (!base)
                return -ENOMEM;

        msc = devm_kzalloc(dev, sizeof(*msc), GFP_KERNEL);
        if (!msc)
                return -ENOMEM;

        res = intel_th_device_get_resource(thdev, IORESOURCE_IRQ, 1);
        if (!res)
                msc->do_irq = 1;

        msc->index = thdev->id;

        msc->thdev = thdev;
        msc->reg_base = base + msc->index * 0x100;
        msc->msu_base = base;

        INIT_WORK(&msc->work, msc_work);
        err = intel_th_msc_init(msc);
        if (err)
                return err;

        dev_set_drvdata(dev, msc);

        return 0;
}

static void intel_th_msc_remove(struct intel_th_device *thdev)
{
        struct msc *msc = dev_get_drvdata(&thdev->dev);
        int ret;

        intel_th_msc_deactivate(thdev);

        /*
         * Buffers should not be used at this point except if the
         * output character device is still open and the parent
         * device gets detached from its bus, which is a FIXME.
         */
        ret = msc_buffer_free_unless_used(msc);
        WARN_ON_ONCE(ret);
}

static struct intel_th_driver intel_th_msc_driver = {
        .probe  = intel_th_msc_probe,
        .remove = intel_th_msc_remove,
        .irq            = intel_th_msc_interrupt,
        .wait_empty     = intel_th_msc_wait_empty,
        .activate       = intel_th_msc_activate,
        .deactivate     = intel_th_msc_deactivate,
        .fops   = &intel_th_msc_fops,
        .attr_group     = &msc_output_group,
        .driver = {
                .name   = "msc",
                .owner  = THIS_MODULE,
        },
};

module_driver(intel_th_msc_driver,
              intel_th_driver_register,
              intel_th_driver_unregister);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Intel(R) Trace Hub Memory Storage Unit driver");
MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");