Linux 3.18.139

[linux/fpc-iii.git] / drivers / dma / qcom_bam_dma.c

/*
 * Copyright (c) 2013-2014, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 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.
 *
 */
/*
 * QCOM BAM DMA engine driver
 *
 * QCOM BAM DMA blocks are distributed amongst a number of the on-chip
 * peripherals on the MSM 8x74.  The configuration of the channels are dependent
 * on the way they are hard wired to that specific peripheral.  The peripheral
 * device tree entries specify the configuration of each channel.
 *
 * The DMA controller requires the use of external memory for storage of the
 * hardware descriptors for each channel.  The descriptor FIFO is accessed as a
 * circular buffer and operations are managed according to the offset within the
 * FIFO.  After pipe/channel reset, all of the pipe registers and internal state
 * are back to defaults.
 *
 * During DMA operations, we write descriptors to the FIFO, being careful to
 * handle wrapping and then write the last FIFO offset to that channel's
 * P_EVNT_REG register to kick off the transaction.  The P_SW_OFSTS register
 * indicates the current FIFO offset that is being processed, so there is some
 * indication of where the hardware is currently working.
 */

#include <linux/kernel.h>
#include <linux/io.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_dma.h>
#include <linux/clk.h>
#include <linux/dmaengine.h>

#include "dmaengine.h"
#include "virt-dma.h"

struct bam_desc_hw {
        u32 addr;               /* Buffer physical address */
        u16 size;               /* Buffer size in bytes */
        u16 flags;
};

#define DESC_FLAG_INT BIT(15)
#define DESC_FLAG_EOT BIT(14)
#define DESC_FLAG_EOB BIT(13)
#define DESC_FLAG_NWD BIT(12)

struct bam_async_desc {
        struct virt_dma_desc vd;

        u32 num_desc;
        u32 xfer_len;

        /* transaction flags, EOT|EOB|NWD */
        u16 flags;

        struct bam_desc_hw *curr_desc;

        enum dma_transfer_direction dir;
        size_t length;
        struct bam_desc_hw desc[0];
};

#define BAM_CTRL                        0x0000
#define BAM_REVISION                    0x0004
#define BAM_SW_REVISION                 0x0080
#define BAM_NUM_PIPES                   0x003C
#define BAM_TIMER                       0x0040
#define BAM_TIMER_CTRL                  0x0044
#define BAM_DESC_CNT_TRSHLD             0x0008
#define BAM_IRQ_SRCS                    0x000C
#define BAM_IRQ_SRCS_MSK                0x0010
#define BAM_IRQ_SRCS_UNMASKED           0x0030
#define BAM_IRQ_STTS                    0x0014
#define BAM_IRQ_CLR                     0x0018
#define BAM_IRQ_EN                      0x001C
#define BAM_CNFG_BITS                   0x007C
#define BAM_IRQ_SRCS_EE(ee)             (0x0800 + ((ee) * 0x80))
#define BAM_IRQ_SRCS_MSK_EE(ee)         (0x0804 + ((ee) * 0x80))
#define BAM_P_CTRL(pipe)                (0x1000 + ((pipe) * 0x1000))
#define BAM_P_RST(pipe)                 (0x1004 + ((pipe) * 0x1000))
#define BAM_P_HALT(pipe)                (0x1008 + ((pipe) * 0x1000))
#define BAM_P_IRQ_STTS(pipe)            (0x1010 + ((pipe) * 0x1000))
#define BAM_P_IRQ_CLR(pipe)             (0x1014 + ((pipe) * 0x1000))
#define BAM_P_IRQ_EN(pipe)              (0x1018 + ((pipe) * 0x1000))
#define BAM_P_EVNT_DEST_ADDR(pipe)      (0x182C + ((pipe) * 0x1000))
#define BAM_P_EVNT_REG(pipe)            (0x1818 + ((pipe) * 0x1000))
#define BAM_P_SW_OFSTS(pipe)            (0x1800 + ((pipe) * 0x1000))
#define BAM_P_DATA_FIFO_ADDR(pipe)      (0x1824 + ((pipe) * 0x1000))
#define BAM_P_DESC_FIFO_ADDR(pipe)      (0x181C + ((pipe) * 0x1000))
#define BAM_P_EVNT_TRSHLD(pipe)         (0x1828 + ((pipe) * 0x1000))
#define BAM_P_FIFO_SIZES(pipe)          (0x1820 + ((pipe) * 0x1000))

/* BAM CTRL */
#define BAM_SW_RST                      BIT(0)
#define BAM_EN                          BIT(1)
#define BAM_EN_ACCUM                    BIT(4)
#define BAM_TESTBUS_SEL_SHIFT           5
#define BAM_TESTBUS_SEL_MASK            0x3F
#define BAM_DESC_CACHE_SEL_SHIFT        13
#define BAM_DESC_CACHE_SEL_MASK         0x3
#define BAM_CACHED_DESC_STORE           BIT(15)
#define IBC_DISABLE                     BIT(16)

/* BAM REVISION */
#define REVISION_SHIFT          0
#define REVISION_MASK           0xFF
#define NUM_EES_SHIFT           8
#define NUM_EES_MASK            0xF
#define CE_BUFFER_SIZE          BIT(13)
#define AXI_ACTIVE              BIT(14)
#define USE_VMIDMT              BIT(15)
#define SECURED                 BIT(16)
#define BAM_HAS_NO_BYPASS       BIT(17)
#define HIGH_FREQUENCY_BAM      BIT(18)
#define INACTIV_TMRS_EXST       BIT(19)
#define NUM_INACTIV_TMRS        BIT(20)
#define DESC_CACHE_DEPTH_SHIFT  21
#define DESC_CACHE_DEPTH_1      (0 << DESC_CACHE_DEPTH_SHIFT)
#define DESC_CACHE_DEPTH_2      (1 << DESC_CACHE_DEPTH_SHIFT)
#define DESC_CACHE_DEPTH_3      (2 << DESC_CACHE_DEPTH_SHIFT)
#define DESC_CACHE_DEPTH_4      (3 << DESC_CACHE_DEPTH_SHIFT)
#define CMD_DESC_EN             BIT(23)
#define INACTIV_TMR_BASE_SHIFT  24
#define INACTIV_TMR_BASE_MASK   0xFF

/* BAM NUM PIPES */
#define BAM_NUM_PIPES_SHIFT             0
#define BAM_NUM_PIPES_MASK              0xFF
#define PERIPH_NON_PIPE_GRP_SHIFT       16
#define PERIPH_NON_PIP_GRP_MASK         0xFF
#define BAM_NON_PIPE_GRP_SHIFT          24
#define BAM_NON_PIPE_GRP_MASK           0xFF

/* BAM CNFG BITS */
#define BAM_PIPE_CNFG           BIT(2)
#define BAM_FULL_PIPE           BIT(11)
#define BAM_NO_EXT_P_RST        BIT(12)
#define BAM_IBC_DISABLE         BIT(13)
#define BAM_SB_CLK_REQ          BIT(14)
#define BAM_PSM_CSW_REQ         BIT(15)
#define BAM_PSM_P_RES           BIT(16)
#define BAM_AU_P_RES            BIT(17)
#define BAM_SI_P_RES            BIT(18)
#define BAM_WB_P_RES            BIT(19)
#define BAM_WB_BLK_CSW          BIT(20)
#define BAM_WB_CSW_ACK_IDL      BIT(21)
#define BAM_WB_RETR_SVPNT       BIT(22)
#define BAM_WB_DSC_AVL_P_RST    BIT(23)
#define BAM_REG_P_EN            BIT(24)
#define BAM_PSM_P_HD_DATA       BIT(25)
#define BAM_AU_ACCUMED          BIT(26)
#define BAM_CMD_ENABLE          BIT(27)

#define BAM_CNFG_BITS_DEFAULT   (BAM_PIPE_CNFG |        \
                                 BAM_NO_EXT_P_RST |     \
                                 BAM_IBC_DISABLE |      \
                                 BAM_SB_CLK_REQ |       \
                                 BAM_PSM_CSW_REQ |      \
                                 BAM_PSM_P_RES |        \
                                 BAM_AU_P_RES |         \
                                 BAM_SI_P_RES |         \
                                 BAM_WB_P_RES |         \
                                 BAM_WB_BLK_CSW |       \
                                 BAM_WB_CSW_ACK_IDL |   \
                                 BAM_WB_RETR_SVPNT |    \
                                 BAM_WB_DSC_AVL_P_RST | \
                                 BAM_REG_P_EN |         \
                                 BAM_PSM_P_HD_DATA |    \
                                 BAM_AU_ACCUMED |       \
                                 BAM_CMD_ENABLE)

/* PIPE CTRL */
#define P_EN                    BIT(1)
#define P_DIRECTION             BIT(3)
#define P_SYS_STRM              BIT(4)
#define P_SYS_MODE              BIT(5)
#define P_AUTO_EOB              BIT(6)
#define P_AUTO_EOB_SEL_SHIFT    7
#define P_AUTO_EOB_SEL_512      (0 << P_AUTO_EOB_SEL_SHIFT)
#define P_AUTO_EOB_SEL_256      (1 << P_AUTO_EOB_SEL_SHIFT)
#define P_AUTO_EOB_SEL_128      (2 << P_AUTO_EOB_SEL_SHIFT)
#define P_AUTO_EOB_SEL_64       (3 << P_AUTO_EOB_SEL_SHIFT)
#define P_PREFETCH_LIMIT_SHIFT  9
#define P_PREFETCH_LIMIT_32     (0 << P_PREFETCH_LIMIT_SHIFT)
#define P_PREFETCH_LIMIT_16     (1 << P_PREFETCH_LIMIT_SHIFT)
#define P_PREFETCH_LIMIT_4      (2 << P_PREFETCH_LIMIT_SHIFT)
#define P_WRITE_NWD             BIT(11)
#define P_LOCK_GROUP_SHIFT      16
#define P_LOCK_GROUP_MASK       0x1F

/* BAM_DESC_CNT_TRSHLD */
#define CNT_TRSHLD              0xffff
#define DEFAULT_CNT_THRSHLD     0x4

/* BAM_IRQ_SRCS */
#define BAM_IRQ                 BIT(31)
#define P_IRQ                   0x7fffffff

/* BAM_IRQ_SRCS_MSK */
#define BAM_IRQ_MSK             BAM_IRQ
#define P_IRQ_MSK               P_IRQ

/* BAM_IRQ_STTS */
#define BAM_TIMER_IRQ           BIT(4)
#define BAM_EMPTY_IRQ           BIT(3)
#define BAM_ERROR_IRQ           BIT(2)
#define BAM_HRESP_ERR_IRQ       BIT(1)

/* BAM_IRQ_CLR */
#define BAM_TIMER_CLR           BIT(4)
#define BAM_EMPTY_CLR           BIT(3)
#define BAM_ERROR_CLR           BIT(2)
#define BAM_HRESP_ERR_CLR       BIT(1)

/* BAM_IRQ_EN */
#define BAM_TIMER_EN            BIT(4)
#define BAM_EMPTY_EN            BIT(3)
#define BAM_ERROR_EN            BIT(2)
#define BAM_HRESP_ERR_EN        BIT(1)

/* BAM_P_IRQ_EN */
#define P_PRCSD_DESC_EN         BIT(0)
#define P_TIMER_EN              BIT(1)
#define P_WAKE_EN               BIT(2)
#define P_OUT_OF_DESC_EN        BIT(3)
#define P_ERR_EN                BIT(4)
#define P_TRNSFR_END_EN         BIT(5)
#define P_DEFAULT_IRQS_EN       (P_PRCSD_DESC_EN | P_ERR_EN | P_TRNSFR_END_EN)

/* BAM_P_SW_OFSTS */
#define P_SW_OFSTS_MASK         0xffff

#define BAM_DESC_FIFO_SIZE      SZ_32K
#define MAX_DESCRIPTORS (BAM_DESC_FIFO_SIZE / sizeof(struct bam_desc_hw) - 1)
#define BAM_MAX_DATA_SIZE       (SZ_32K - 8)

struct bam_chan {
        struct virt_dma_chan vc;

        struct bam_device *bdev;

        /* configuration from device tree */
        u32 id;

        struct bam_async_desc *curr_txd;        /* current running dma */

        /* runtime configuration */
        struct dma_slave_config slave;

        /* fifo storage */
        struct bam_desc_hw *fifo_virt;
        dma_addr_t fifo_phys;

        /* fifo markers */
        unsigned short head;            /* start of active descriptor entries */
        unsigned short tail;            /* end of active descriptor entries */

        unsigned int initialized;       /* is the channel hw initialized? */
        unsigned int paused;            /* is the channel paused? */
        unsigned int reconfigure;       /* new slave config? */

        struct list_head node;
};

static inline struct bam_chan *to_bam_chan(struct dma_chan *common)
{
        return container_of(common, struct bam_chan, vc.chan);
}

struct bam_device {
        void __iomem *regs;
        struct device *dev;
        struct dma_device common;
        struct device_dma_parameters dma_parms;
        struct bam_chan *channels;
        u32 num_channels;

        /* execution environment ID, from DT */
        u32 ee;

        struct clk *bamclk;
        int irq;

        /* dma start transaction tasklet */
        struct tasklet_struct task;
};

/**
 * bam_reset_channel - Reset individual BAM DMA channel
 * @bchan: bam channel
 *
 * This function resets a specific BAM channel
 */
static void bam_reset_channel(struct bam_chan *bchan)
{
        struct bam_device *bdev = bchan->bdev;

        lockdep_assert_held(&bchan->vc.lock);

        /* reset channel */
        writel_relaxed(1, bdev->regs + BAM_P_RST(bchan->id));
        writel_relaxed(0, bdev->regs + BAM_P_RST(bchan->id));

        /* don't allow cpu to reorder BAM register accesses done after this */
        wmb();

        /* make sure hw is initialized when channel is used the first time  */
        bchan->initialized = 0;
}

/**
 * bam_chan_init_hw - Initialize channel hardware
 * @bchan: bam channel
 *
 * This function resets and initializes the BAM channel
 */
static void bam_chan_init_hw(struct bam_chan *bchan,
        enum dma_transfer_direction dir)
{
        struct bam_device *bdev = bchan->bdev;
        u32 val;

        /* Reset the channel to clear internal state of the FIFO */
        bam_reset_channel(bchan);

        /*
         * write out 8 byte aligned address.  We have enough space for this
         * because we allocated 1 more descriptor (8 bytes) than we can use
         */
        writel_relaxed(ALIGN(bchan->fifo_phys, sizeof(struct bam_desc_hw)),
                        bdev->regs + BAM_P_DESC_FIFO_ADDR(bchan->id));
        writel_relaxed(BAM_DESC_FIFO_SIZE, bdev->regs +
                        BAM_P_FIFO_SIZES(bchan->id));

        /* enable the per pipe interrupts, enable EOT, ERR, and INT irqs */
        writel_relaxed(P_DEFAULT_IRQS_EN, bdev->regs + BAM_P_IRQ_EN(bchan->id));

        /* unmask the specific pipe and EE combo */
        val = readl_relaxed(bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));
        val |= BIT(bchan->id);
        writel_relaxed(val, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));

        /* don't allow cpu to reorder the channel enable done below */
        wmb();

        /* set fixed direction and mode, then enable channel */
        val = P_EN | P_SYS_MODE;
        if (dir == DMA_DEV_TO_MEM)
                val |= P_DIRECTION;

        writel_relaxed(val, bdev->regs + BAM_P_CTRL(bchan->id));

        bchan->initialized = 1;

        /* init FIFO pointers */
        bchan->head = 0;
        bchan->tail = 0;
}

/**
 * bam_alloc_chan - Allocate channel resources for DMA channel.
 * @chan: specified channel
 *
 * This function allocates the FIFO descriptor memory
 */
static int bam_alloc_chan(struct dma_chan *chan)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        struct bam_device *bdev = bchan->bdev;

        if (bchan->fifo_virt)
                return 0;

        /* allocate FIFO descriptor space, but only if necessary */
        bchan->fifo_virt = dma_alloc_writecombine(bdev->dev, BAM_DESC_FIFO_SIZE,
                                &bchan->fifo_phys, GFP_KERNEL);

        if (!bchan->fifo_virt) {
                dev_err(bdev->dev, "Failed to allocate desc fifo\n");
                return -ENOMEM;
        }

        return 0;
}

/**
 * bam_free_chan - Frees dma resources associated with specific channel
 * @chan: specified channel
 *
 * Free the allocated fifo descriptor memory and channel resources
 *
 */
static void bam_free_chan(struct dma_chan *chan)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        struct bam_device *bdev = bchan->bdev;
        u32 val;
        unsigned long flags;

        vchan_free_chan_resources(to_virt_chan(chan));

        if (bchan->curr_txd) {
                dev_err(bchan->bdev->dev, "Cannot free busy channel\n");
                return;
        }

        spin_lock_irqsave(&bchan->vc.lock, flags);
        bam_reset_channel(bchan);
        spin_unlock_irqrestore(&bchan->vc.lock, flags);

        dma_free_writecombine(bdev->dev, BAM_DESC_FIFO_SIZE, bchan->fifo_virt,
                                bchan->fifo_phys);
        bchan->fifo_virt = NULL;

        /* mask irq for pipe/channel */
        val = readl_relaxed(bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));
        val &= ~BIT(bchan->id);
        writel_relaxed(val, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));

        /* disable irq */
        writel_relaxed(0, bdev->regs + BAM_P_IRQ_EN(bchan->id));
}

/**
 * bam_slave_config - set slave configuration for channel
 * @chan: dma channel
 * @cfg: slave configuration
 *
 * Sets slave configuration for channel
 *
 */
static void bam_slave_config(struct bam_chan *bchan,
                struct dma_slave_config *cfg)
{
        memcpy(&bchan->slave, cfg, sizeof(*cfg));
        bchan->reconfigure = 1;
}

/**
 * bam_prep_slave_sg - Prep slave sg transaction
 *
 * @chan: dma channel
 * @sgl: scatter gather list
 * @sg_len: length of sg
 * @direction: DMA transfer direction
 * @flags: DMA flags
 * @context: transfer context (unused)
 */
static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
        struct scatterlist *sgl, unsigned int sg_len,
        enum dma_transfer_direction direction, unsigned long flags,
        void *context)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        struct bam_device *bdev = bchan->bdev;
        struct bam_async_desc *async_desc;
        struct scatterlist *sg;
        u32 i;
        struct bam_desc_hw *desc;
        unsigned int num_alloc = 0;


        if (!is_slave_direction(direction)) {
                dev_err(bdev->dev, "invalid dma direction\n");
                return NULL;
        }

        /* calculate number of required entries */
        for_each_sg(sgl, sg, sg_len, i)
                num_alloc += DIV_ROUND_UP(sg_dma_len(sg), BAM_MAX_DATA_SIZE);

        /* allocate enough room to accomodate the number of entries */
        async_desc = kzalloc(sizeof(*async_desc) +
                        (num_alloc * sizeof(struct bam_desc_hw)), GFP_NOWAIT);

        if (!async_desc)
                goto err_out;

        if (flags & DMA_PREP_FENCE)
                async_desc->flags |= DESC_FLAG_NWD;

        if (flags & DMA_PREP_INTERRUPT)
                async_desc->flags |= DESC_FLAG_EOT;
        else
                async_desc->flags |= DESC_FLAG_INT;

        async_desc->num_desc = num_alloc;
        async_desc->curr_desc = async_desc->desc;
        async_desc->dir = direction;

        /* fill in temporary descriptors */
        desc = async_desc->desc;
        for_each_sg(sgl, sg, sg_len, i) {
                unsigned int remainder = sg_dma_len(sg);
                unsigned int curr_offset = 0;

                do {
                        desc->addr = sg_dma_address(sg) + curr_offset;

                        if (remainder > BAM_MAX_DATA_SIZE) {
                                desc->size = BAM_MAX_DATA_SIZE;
                                remainder -= BAM_MAX_DATA_SIZE;
                                curr_offset += BAM_MAX_DATA_SIZE;
                        } else {
                                desc->size = remainder;
                                remainder = 0;
                        }

                        async_desc->length += desc->size;
                        desc++;
                } while (remainder > 0);
        }

        return vchan_tx_prep(&bchan->vc, &async_desc->vd, flags);

err_out:
        kfree(async_desc);
        return NULL;
}

/**
 * bam_dma_terminate_all - terminate all transactions on a channel
 * @bchan: bam dma channel
 *
 * Dequeues and frees all transactions
 * No callbacks are done
 *
 */
static void bam_dma_terminate_all(struct bam_chan *bchan)
{
        unsigned long flag;
        LIST_HEAD(head);

        /* remove all transactions, including active transaction */
        spin_lock_irqsave(&bchan->vc.lock, flag);
        if (bchan->curr_txd) {
                list_add(&bchan->curr_txd->vd.node, &bchan->vc.desc_issued);
                bchan->curr_txd = NULL;
        }

        vchan_get_all_descriptors(&bchan->vc, &head);
        spin_unlock_irqrestore(&bchan->vc.lock, flag);

        vchan_dma_desc_free_list(&bchan->vc, &head);
}

/**
 * bam_control - DMA device control
 * @chan: dma channel
 * @cmd: control cmd
 * @arg: cmd argument
 *
 * Perform DMA control command
 *
 */
static int bam_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
        unsigned long arg)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        struct bam_device *bdev = bchan->bdev;
        int ret = 0;
        unsigned long flag;

        switch (cmd) {
        case DMA_PAUSE:
                spin_lock_irqsave(&bchan->vc.lock, flag);
                writel_relaxed(1, bdev->regs + BAM_P_HALT(bchan->id));
                bchan->paused = 1;
                spin_unlock_irqrestore(&bchan->vc.lock, flag);
                break;

        case DMA_RESUME:
                spin_lock_irqsave(&bchan->vc.lock, flag);
                writel_relaxed(0, bdev->regs + BAM_P_HALT(bchan->id));
                bchan->paused = 0;
                spin_unlock_irqrestore(&bchan->vc.lock, flag);
                break;

        case DMA_TERMINATE_ALL:
                bam_dma_terminate_all(bchan);
                break;

        case DMA_SLAVE_CONFIG:
                spin_lock_irqsave(&bchan->vc.lock, flag);
                bam_slave_config(bchan, (struct dma_slave_config *)arg);
                spin_unlock_irqrestore(&bchan->vc.lock, flag);
                break;

        default:
                ret = -ENXIO;
                break;
        }

        return ret;
}

/**
 * process_channel_irqs - processes the channel interrupts
 * @bdev: bam controller
 *
 * This function processes the channel interrupts
 *
 */
static u32 process_channel_irqs(struct bam_device *bdev)
{
        u32 i, srcs, pipe_stts;
        unsigned long flags;
        struct bam_async_desc *async_desc;

        srcs = readl_relaxed(bdev->regs + BAM_IRQ_SRCS_EE(bdev->ee));

        /* return early if no pipe/channel interrupts are present */
        if (!(srcs & P_IRQ))
                return srcs;

        for (i = 0; i < bdev->num_channels; i++) {
                struct bam_chan *bchan = &bdev->channels[i];

                if (!(srcs & BIT(i)))
                        continue;

                /* clear pipe irq */
                pipe_stts = readl_relaxed(bdev->regs +
                        BAM_P_IRQ_STTS(i));

                writel_relaxed(pipe_stts, bdev->regs +
                                BAM_P_IRQ_CLR(i));

                spin_lock_irqsave(&bchan->vc.lock, flags);
                async_desc = bchan->curr_txd;

                if (async_desc) {
                        async_desc->num_desc -= async_desc->xfer_len;
                        async_desc->curr_desc += async_desc->xfer_len;
                        bchan->curr_txd = NULL;

                        /* manage FIFO */
                        bchan->head += async_desc->xfer_len;
                        bchan->head %= MAX_DESCRIPTORS;

                        /*
                         * if complete, process cookie.  Otherwise
                         * push back to front of desc_issued so that
                         * it gets restarted by the tasklet
                         */
                        if (!async_desc->num_desc)
                                vchan_cookie_complete(&async_desc->vd);
                        else
                                list_add(&async_desc->vd.node,
                                        &bchan->vc.desc_issued);
                }

                spin_unlock_irqrestore(&bchan->vc.lock, flags);
        }

        return srcs;
}

/**
 * bam_dma_irq - irq handler for bam controller
 * @irq: IRQ of interrupt
 * @data: callback data
 *
 * IRQ handler for the bam controller
 */
static irqreturn_t bam_dma_irq(int irq, void *data)
{
        struct bam_device *bdev = data;
        u32 clr_mask = 0, srcs = 0;

        srcs |= process_channel_irqs(bdev);

        /* kick off tasklet to start next dma transfer */
        if (srcs & P_IRQ)
                tasklet_schedule(&bdev->task);

        if (srcs & BAM_IRQ)
                clr_mask = readl_relaxed(bdev->regs + BAM_IRQ_STTS);

        /* don't allow reorder of the various accesses to the BAM registers */
        mb();

        writel_relaxed(clr_mask, bdev->regs + BAM_IRQ_CLR);

        return IRQ_HANDLED;
}

/**
 * bam_tx_status - returns status of transaction
 * @chan: dma channel
 * @cookie: transaction cookie
 * @txstate: DMA transaction state
 *
 * Return status of dma transaction
 */
static enum dma_status bam_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
                struct dma_tx_state *txstate)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        struct virt_dma_desc *vd;
        int ret;
        size_t residue = 0;
        unsigned int i;
        unsigned long flags;

        ret = dma_cookie_status(chan, cookie, txstate);
        if (ret == DMA_COMPLETE)
                return ret;

        if (!txstate)
                return bchan->paused ? DMA_PAUSED : ret;

        spin_lock_irqsave(&bchan->vc.lock, flags);
        vd = vchan_find_desc(&bchan->vc, cookie);
        if (vd)
                residue = container_of(vd, struct bam_async_desc, vd)->length;
        else if (bchan->curr_txd && bchan->curr_txd->vd.tx.cookie == cookie)
                for (i = 0; i < bchan->curr_txd->num_desc; i++)
                        residue += bchan->curr_txd->curr_desc[i].size;

        spin_unlock_irqrestore(&bchan->vc.lock, flags);

        dma_set_residue(txstate, residue);

        if (ret == DMA_IN_PROGRESS && bchan->paused)
                ret = DMA_PAUSED;

        return ret;
}

/**
 * bam_apply_new_config
 * @bchan: bam dma channel
 * @dir: DMA direction
 */
static void bam_apply_new_config(struct bam_chan *bchan,
        enum dma_transfer_direction dir)
{
        struct bam_device *bdev = bchan->bdev;
        u32 maxburst;

        if (dir == DMA_DEV_TO_MEM)
                maxburst = bchan->slave.src_maxburst;
        else
                maxburst = bchan->slave.dst_maxburst;

        writel_relaxed(maxburst, bdev->regs + BAM_DESC_CNT_TRSHLD);

        bchan->reconfigure = 0;
}

/**
 * bam_start_dma - start next transaction
 * @bchan - bam dma channel
 */
static void bam_start_dma(struct bam_chan *bchan)
{
        struct virt_dma_desc *vd = vchan_next_desc(&bchan->vc);
        struct bam_device *bdev = bchan->bdev;
        struct bam_async_desc *async_desc;
        struct bam_desc_hw *desc;
        struct bam_desc_hw *fifo = PTR_ALIGN(bchan->fifo_virt,
                                        sizeof(struct bam_desc_hw));

        lockdep_assert_held(&bchan->vc.lock);

        if (!vd)
                return;

        list_del(&vd->node);

        async_desc = container_of(vd, struct bam_async_desc, vd);
        bchan->curr_txd = async_desc;

        /* on first use, initialize the channel hardware */
        if (!bchan->initialized)
                bam_chan_init_hw(bchan, async_desc->dir);

        /* apply new slave config changes, if necessary */
        if (bchan->reconfigure)
                bam_apply_new_config(bchan, async_desc->dir);

        desc = bchan->curr_txd->curr_desc;

        if (async_desc->num_desc > MAX_DESCRIPTORS)
                async_desc->xfer_len = MAX_DESCRIPTORS;
        else
                async_desc->xfer_len = async_desc->num_desc;

        /* set any special flags on the last descriptor */
        if (async_desc->num_desc == async_desc->xfer_len)
                desc[async_desc->xfer_len - 1].flags = async_desc->flags;
        else
                desc[async_desc->xfer_len - 1].flags |= DESC_FLAG_INT;

        if (bchan->tail + async_desc->xfer_len > MAX_DESCRIPTORS) {
                u32 partial = MAX_DESCRIPTORS - bchan->tail;

                memcpy(&fifo[bchan->tail], desc,
                                partial * sizeof(struct bam_desc_hw));
                memcpy(fifo, &desc[partial], (async_desc->xfer_len - partial) *
                                sizeof(struct bam_desc_hw));
        } else {
                memcpy(&fifo[bchan->tail], desc,
                        async_desc->xfer_len * sizeof(struct bam_desc_hw));
        }

        bchan->tail += async_desc->xfer_len;
        bchan->tail %= MAX_DESCRIPTORS;

        /* ensure descriptor writes and dma start not reordered */
        wmb();
        writel_relaxed(bchan->tail * sizeof(struct bam_desc_hw),
                        bdev->regs + BAM_P_EVNT_REG(bchan->id));
}

/**
 * dma_tasklet - DMA IRQ tasklet
 * @data: tasklet argument (bam controller structure)
 *
 * Sets up next DMA operation and then processes all completed transactions
 */
static void dma_tasklet(unsigned long data)
{
        struct bam_device *bdev = (struct bam_device *)data;
        struct bam_chan *bchan;
        unsigned long flags;
        unsigned int i;

        /* go through the channels and kick off transactions */
        for (i = 0; i < bdev->num_channels; i++) {
                bchan = &bdev->channels[i];
                spin_lock_irqsave(&bchan->vc.lock, flags);

                if (!list_empty(&bchan->vc.desc_issued) && !bchan->curr_txd)
                        bam_start_dma(bchan);
                spin_unlock_irqrestore(&bchan->vc.lock, flags);
        }
}

/**
 * bam_issue_pending - starts pending transactions
 * @chan: dma channel
 *
 * Calls tasklet directly which in turn starts any pending transactions
 */
static void bam_issue_pending(struct dma_chan *chan)
{
        struct bam_chan *bchan = to_bam_chan(chan);
        unsigned long flags;

        spin_lock_irqsave(&bchan->vc.lock, flags);

        /* if work pending and idle, start a transaction */
        if (vchan_issue_pending(&bchan->vc) && !bchan->curr_txd)
                bam_start_dma(bchan);

        spin_unlock_irqrestore(&bchan->vc.lock, flags);
}

/**
 * bam_dma_free_desc - free descriptor memory
 * @vd: virtual descriptor
 *
 */
static void bam_dma_free_desc(struct virt_dma_desc *vd)
{
        struct bam_async_desc *async_desc = container_of(vd,
                        struct bam_async_desc, vd);

        kfree(async_desc);
}

static struct dma_chan *bam_dma_xlate(struct of_phandle_args *dma_spec,
                struct of_dma *of)
{
        struct bam_device *bdev = container_of(of->of_dma_data,
                                        struct bam_device, common);
        unsigned int request;

        if (dma_spec->args_count != 1)
                return NULL;

        request = dma_spec->args[0];
        if (request >= bdev->num_channels)
                return NULL;

        return dma_get_slave_channel(&(bdev->channels[request].vc.chan));
}

/**
 * bam_init
 * @bdev: bam device
 *
 * Initialization helper for global bam registers
 */
static int bam_init(struct bam_device *bdev)
{
        u32 val;

        /* read revision and configuration information */
        val = readl_relaxed(bdev->regs + BAM_REVISION) >> NUM_EES_SHIFT;
        val &= NUM_EES_MASK;

        /* check that configured EE is within range */
        if (bdev->ee >= val)
                return -EINVAL;

        val = readl_relaxed(bdev->regs + BAM_NUM_PIPES);
        bdev->num_channels = val & BAM_NUM_PIPES_MASK;

        /* s/w reset bam */
        /* after reset all pipes are disabled and idle */
        val = readl_relaxed(bdev->regs + BAM_CTRL);
        val |= BAM_SW_RST;
        writel_relaxed(val, bdev->regs + BAM_CTRL);
        val &= ~BAM_SW_RST;
        writel_relaxed(val, bdev->regs + BAM_CTRL);

        /* make sure previous stores are visible before enabling BAM */
        wmb();

        /* enable bam */
        val |= BAM_EN;
        writel_relaxed(val, bdev->regs + BAM_CTRL);

        /* set descriptor threshhold, start with 4 bytes */
        writel_relaxed(DEFAULT_CNT_THRSHLD, bdev->regs + BAM_DESC_CNT_TRSHLD);

        /* Enable default set of h/w workarounds, ie all except BAM_FULL_PIPE */
        writel_relaxed(BAM_CNFG_BITS_DEFAULT, bdev->regs + BAM_CNFG_BITS);

        /* enable irqs for errors */
        writel_relaxed(BAM_ERROR_EN | BAM_HRESP_ERR_EN,
                                bdev->regs + BAM_IRQ_EN);

        /* unmask global bam interrupt */
        writel_relaxed(BAM_IRQ_MSK, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));

        return 0;
}

static void bam_channel_init(struct bam_device *bdev, struct bam_chan *bchan,
        u32 index)
{
        bchan->id = index;
        bchan->bdev = bdev;

        vchan_init(&bchan->vc, &bdev->common);
        bchan->vc.desc_free = bam_dma_free_desc;
}

static int bam_dma_probe(struct platform_device *pdev)
{
        struct bam_device *bdev;
        struct resource *iores;
        int ret, i;

        bdev = devm_kzalloc(&pdev->dev, sizeof(*bdev), GFP_KERNEL);
        if (!bdev)
                return -ENOMEM;

        bdev->dev = &pdev->dev;

        iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        bdev->regs = devm_ioremap_resource(&pdev->dev, iores);
        if (IS_ERR(bdev->regs))
                return PTR_ERR(bdev->regs);

        bdev->irq = platform_get_irq(pdev, 0);
        if (bdev->irq < 0)
                return bdev->irq;

        ret = of_property_read_u32(pdev->dev.of_node, "qcom,ee", &bdev->ee);
        if (ret) {
                dev_err(bdev->dev, "Execution environment unspecified\n");
                return ret;
        }

        bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
        if (IS_ERR(bdev->bamclk))
                return PTR_ERR(bdev->bamclk);

        ret = clk_prepare_enable(bdev->bamclk);
        if (ret) {
                dev_err(bdev->dev, "failed to prepare/enable clock\n");
                return ret;
        }

        ret = bam_init(bdev);
        if (ret)
                goto err_disable_clk;

        tasklet_init(&bdev->task, dma_tasklet, (unsigned long)bdev);

        bdev->channels = devm_kcalloc(bdev->dev, bdev->num_channels,
                                sizeof(*bdev->channels), GFP_KERNEL);

        if (!bdev->channels) {
                ret = -ENOMEM;
                goto err_disable_clk;
        }

        /* allocate and initialize channels */
        INIT_LIST_HEAD(&bdev->common.channels);

        for (i = 0; i < bdev->num_channels; i++)
                bam_channel_init(bdev, &bdev->channels[i], i);

        ret = devm_request_irq(bdev->dev, bdev->irq, bam_dma_irq,
                        IRQF_TRIGGER_HIGH, "bam_dma", bdev);
        if (ret)
                goto err_disable_clk;

        /* set max dma segment size */
        bdev->common.dev = bdev->dev;
        bdev->common.dev->dma_parms = &bdev->dma_parms;
        ret = dma_set_max_seg_size(bdev->common.dev, BAM_MAX_DATA_SIZE);
        if (ret) {
                dev_err(bdev->dev, "cannot set maximum segment size\n");
                goto err_disable_clk;
        }

        platform_set_drvdata(pdev, bdev);

        /* set capabilities */
        dma_cap_zero(bdev->common.cap_mask);
        dma_cap_set(DMA_SLAVE, bdev->common.cap_mask);

        /* initialize dmaengine apis */
        bdev->common.device_alloc_chan_resources = bam_alloc_chan;
        bdev->common.device_free_chan_resources = bam_free_chan;
        bdev->common.device_prep_slave_sg = bam_prep_slave_sg;
        bdev->common.device_control = bam_control;
        bdev->common.device_issue_pending = bam_issue_pending;
        bdev->common.device_tx_status = bam_tx_status;
        bdev->common.dev = bdev->dev;

        ret = dma_async_device_register(&bdev->common);
        if (ret) {
                dev_err(bdev->dev, "failed to register dma async device\n");
                goto err_disable_clk;
        }

        ret = of_dma_controller_register(pdev->dev.of_node, bam_dma_xlate,
                                        &bdev->common);
        if (ret)
                goto err_unregister_dma;

        return 0;

err_unregister_dma:
        dma_async_device_unregister(&bdev->common);
err_disable_clk:
        clk_disable_unprepare(bdev->bamclk);
        return ret;
}

static int bam_dma_remove(struct platform_device *pdev)
{
        struct bam_device *bdev = platform_get_drvdata(pdev);
        u32 i;

        of_dma_controller_free(pdev->dev.of_node);
        dma_async_device_unregister(&bdev->common);

        /* mask all interrupts for this execution environment */
        writel_relaxed(0, bdev->regs + BAM_IRQ_SRCS_MSK_EE(bdev->ee));

        devm_free_irq(bdev->dev, bdev->irq, bdev);

        for (i = 0; i < bdev->num_channels; i++) {
                bam_dma_terminate_all(&bdev->channels[i]);
                tasklet_kill(&bdev->channels[i].vc.task);

                dma_free_writecombine(bdev->dev, BAM_DESC_FIFO_SIZE,
                        bdev->channels[i].fifo_virt,
                        bdev->channels[i].fifo_phys);
        }

        tasklet_kill(&bdev->task);

        clk_disable_unprepare(bdev->bamclk);

        return 0;
}

static const struct of_device_id bam_of_match[] = {
        { .compatible = "qcom,bam-v1.4.0", },
        {}
};
MODULE_DEVICE_TABLE(of, bam_of_match);

static struct platform_driver bam_dma_driver = {
        .probe = bam_dma_probe,
        .remove = bam_dma_remove,
        .driver = {
                .name = "bam-dma-engine",
                .owner = THIS_MODULE,
                .of_match_table = bam_of_match,
        },
};

module_platform_driver(bam_dma_driver);

MODULE_AUTHOR("Andy Gross <agross@codeaurora.org>");
MODULE_DESCRIPTION("QCOM BAM DMA engine driver");
MODULE_LICENSE("GPL v2");