dmaengine: add Qualcomm BAM dma driver

Add the DMA engine driver for the QCOM Bus Access Manager (BAM) DMA controller
found in the MSM 8x74 platforms.

Each BAM DMA device is associated with a specific on-chip peripheral.  Each
channel provides a uni-directional data transfer engine that is capable of
transferring data between the peripheral and system memory (System mode), or
between two peripherals (BAM2BAM).

The initial release of this driver only supports slave transfers between
peripherals and system memory.

Signed-off-by: Andy Gross <agross@codeaurora.org>
Tested-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

3 files changed, 1122 insertions, 0 deletions

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 9bed1a2a67a1..bcdacc73b6a9 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -400,4 +400,13 @@ config DMATEST
 config DMA_ENGINE_RAID
         bool
 
+config QCOM_BAM_DMA
+        tristate "QCOM BAM DMA support"
+        depends on ARCH_QCOM || (COMPILE_TEST && OF && ARM)
+        select DMA_ENGINE
+        select DMA_VIRTUAL_CHANNELS
+        ---help---
+          Enable support for the QCOM BAM DMA controller.  This controller
+          provides DMA capabilities for a variety of on-chip devices.
+
 endif
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index a029d0f4a1be..5150c82c9caf 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -44,3 +44,5 @@ obj-$(CONFIG_DMA_JZ4740) += dma-jz4740.o
 obj-$(CONFIG_TI_CPPI41) += cppi41.o
 obj-$(CONFIG_K3_DMA) += k3dma.o
 obj-$(CONFIG_MOXART_DMA) += moxart-dma.o
+obj-$(CONFIG_FSL_EDMA) += fsl-edma.o
+obj-$(CONFIG_QCOM_BAM_DMA) += qcom_bam_dma.o
diff --git a/drivers/dma/qcom_bam_dma.c b/drivers/dma/qcom_bam_dma.c
new file mode 100644
index 000000000000..82c923146e49
--- /dev/null
+++ b/drivers/dma/qcom_bam_dma.c
@@ -0,0 +1,1111 @@
+/*
+ * 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)
+
+struct bam_async_desc {
+        struct virt_dma_desc vd;
+
+        u32 num_desc;
+        u32 xfer_len;
+        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;
+
+        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 INT on last descriptor */
+        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");