Re: [Patch v1 2/4] dma: tegra: Adding Tegra GPC DMA controller driver

Dmitry Osipenko
2020-07-20T15:12:26Z

Hello, Rajesh!

20.07.2020 09:34, Rajesh Gumasta пишет:
> v4 changes: Removed pending dma desc list and other unused
> data structures
>
> v3 changes: Removed free list for dma_desc and sg

What is this? Isn't it a v1 patch?

You shouldn't include any changelogs into commit message.

In general you may put changelogs under --- below (after commit message)
or have it in a cover-letter.

> Adding GPC DMA controller driver for Tegra186 and Tegra194. The driver
> supports dma transfers between memory to memory, IO to memory and
> memory to IO.
>
> Signed-off-by: Pavan Kunapuli <pkunapuli@nvidia.com>
> Signed-off-by: Rajesh Gumasta <rgumasta@nvidia.com>
> ---
> drivers/dma/Kconfig | 12 +
> drivers/dma/Makefile | 1 +
> drivers/dma/tegra-gpc-dma.c | 1512 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 1525 insertions(+)
> create mode 100644 drivers/dma/tegra-gpc-dma.c
>
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index e9ed916..be4c395 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -639,6 +639,18 @@ config TEGRA210_ADMA
> peripheral and vice versa. It does not support memory to
> memory data transfer.
>
> +config TEGRA_GPC_DMA
> + tristate "NVIDIA Tegra GPC DMA support"
> + depends on ARCH_TEGRA_186_SOC || ARCH_TEGRA_194_SOC || COMPILE_TEST
> + select DMA_ENGINE
> + help
> + Support for the NVIDIA Tegra186 and Tegra194 GPC DMA controller
> + driver. The DMA controller is having multiple DMA channel which
> + can be configured for different peripherals like UART, SPI, etc
> + which are on APB bus.
> + This DMA controller transfers data from memory to peripheral fifo
> + or vice versa. It also supports memory to memory data transfer.
> +
> config TIMB_DMA
> tristate "Timberdale FPGA DMA support"
> depends on MFD_TIMBERDALE || COMPILE_TEST
> diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
> index e60f813..43e3a6e 100644
> --- a/drivers/dma/Makefile
> +++ b/drivers/dma/Makefile
> @@ -76,6 +76,7 @@ obj-$(CONFIG_S3C24XX_DMAC) += s3c24xx-dma.o
> obj-$(CONFIG_TXX9_DMAC) += txx9dmac.o
> obj-$(CONFIG_TEGRA20_APB_DMA) += tegra20-apb-dma.o
> obj-$(CONFIG_TEGRA210_ADMA) += tegra210-adma.o
> +obj-$(CONFIG_TEGRA_GPC_DMA) += tegra-gpc-dma.o
> obj-$(CONFIG_TIMB_DMA) += timb_dma.o
> obj-$(CONFIG_UNIPHIER_MDMAC) += uniphier-mdmac.o
> obj-$(CONFIG_UNIPHIER_XDMAC) += uniphier-xdmac.o
> diff --git a/drivers/dma/tegra-gpc-dma.c b/drivers/dma/tegra-gpc-dma.c
> new file mode 100644
> index 0000000..92b7219
> --- /dev/null
> +++ b/drivers/dma/tegra-gpc-dma.c
> @@ -0,0 +1,1512 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * DMA driver for Nvidia's Tegra186 and Tegra194 GPC DMA controller.
> + *
> + * Copyright (c) 2014-2020, NVIDIA CORPORATION. All rights reserved.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/delay.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +#include <linux/version.h>
> +#include <dt-bindings/memory/tegra186-mc.h>
> +#include "virt-dma.h"
> +
> +/* CSR register */
> +#define TEGRA_GPCDMA_CHAN_CSR 0x00
> +#define TEGRA_GPCDMA_CSR_ENB BIT(31)
> +#define TEGRA_GPCDMA_CSR_IE_EOC BIT(30)
> +#define TEGRA_GPCDMA_CSR_ONCE BIT(27)
> +#define TEGRA_GPCDMA_CSR_FC_MODE_NO_MMIO (0 << 24)
> +#define TEGRA_GPCDMA_CSR_FC_MODE_ONE_MMIO (1 << 24)
> +#define TEGRA_GPCDMA_CSR_FC_MODE_TWO_MMIO (2 << 24)
> +#define TEGRA_GPCDMA_CSR_FC_MODE_FOUR_MMIO (3 << 24)
> +#define TEGRA_GPCDMA_CSR_DMA_IO2MEM_NO_FC (0 << 21)
> +#define TEGRA_GPCDMA_CSR_DMA_IO2MEM_FC (1 << 21)
> +#define TEGRA_GPCDMA_CSR_DMA_MEM2IO_NO_FC (2 << 21)
> +#define TEGRA_GPCDMA_CSR_DMA_MEM2IO_FC (3 << 21)
> +#define TEGRA_GPCDMA_CSR_DMA_MEM2MEM (4 << 21)
> +#define TEGRA_GPCDMA_CSR_DMA_FIXED_PAT (6 << 21)
> +#define TEGRA_GPCDMA_CSR_REQ_SEL_SHIFT 16
> +#define TEGRA_GPCDMA_CSR_REQ_SEL_MASK 0x1F
> +#define TEGRA_GPCDMA_CSR_REQ_SEL_UNUSED 0x4
> +#define TEGRA_GPCDMA_CSR_IRQ_MASK BIT(15)
> +#define TEGRA_GPCDMA_CSR_WEIGHT_SHIFT 10
> +
> +/* STATUS register */
> +#define TEGRA_GPCDMA_CHAN_STATUS 0x004
> +#define TEGRA_GPCDMA_STATUS_BUSY BIT(31)
> +#define TEGRA_GPCDMA_STATUS_ISE_EOC BIT(30)
> +#define TEGRA_GPCDMA_STATUS_PING_PONG BIT(28)
> +#define TEGRA_GPCDMA_STATUS_DMA_ACTIVITY BIT(27)
> +#define TEGRA_GPCDMA_STATUS_CHANNEL_PAUSE BIT(26)
> +#define TEGRA_GPCDMA_STATUS_CHANNEL_RX BIT(25)
> +#define TEGRA_GPCDMA_STATUS_CHANNEL_TX BIT(24)
> +#define TEGRA_GPCDMA_STATUS_IRQ_INTR_STA BIT(23)
> +#define TEGRA_GPCDMA_STATUS_IRQ_STA BIT(21)
> +#define TEGRA_GPCDMA_STATUS_IRQ_TRIG_STA BIT(20)
> +
> +#define TEGRA_GPCDMA_CHAN_CSRE 0x008
> +#define TEGRA_GPCDMA_CHAN_CSRE_PAUSE BIT(31)
> +
> +/* Source address */
> +#define TEGRA_GPCDMA_CHAN_SRC_PTR 0x00C
> +
> +/* Destination address */
> +#define TEGRA_GPCDMA_CHAN_DST_PTR 0x010
> +
> +/* High address pointer */
> +#define TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR 0x014
> +#define TEGRA_GPCDMA_HIGH_ADDR_SCR_PTR_SHIFT 0
> +#define TEGRA_GPCDMA_HIGH_ADDR_SCR_PTR_MASK 0xFF
> +#define TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_SHIFT 16
> +#define TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_MASK 0xFF
> +
> +/* MC sequence register */
> +#define TEGRA_GPCDMA_CHAN_MCSEQ 0x18
> +#define TEGRA_GPCDMA_MCSEQ_DATA_SWAP BIT(31)
> +#define TEGRA_GPCDMA_MCSEQ_REQ_COUNT_SHIFT 25
> +#define TEGRA_GPCDMA_MCSEQ_BURST_2 (0 << 23)
> +#define TEGRA_GPCDMA_MCSEQ_BURST_16 (3 << 23)
> +#define TEGRA_GPCDMA_MCSEQ_WRAP1_SHIFT 20
> +#define TEGRA_GPCDMA_MCSEQ_WRAP0_SHIFT 17
> +#define TEGRA_GPCDMA_MCSEQ_WRAP_NONE 0
> +#define TEGRA_GPCDMA_MCSEQ_MC_PROT_SHIFT 14
> +#define TEGRA_GPCDMA_MCSEQ_STREAM_ID1_SHIFT 7
> +#define TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT 0
> +#define TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK 0x7F
> +
> +/* MMIO sequence register */
> +#define TEGRA_GPCDMA_CHAN_MMIOSEQ 0x01c
> +#define TEGRA_GPCDMA_MMIOSEQ_DBL_BUF BIT(31)
> +#define TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_8 (0 << 28)
> +#define TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_16 (1 << 28)
> +#define TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_32 (2 << 28)
> +#define TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_64 (3 << 28)
> +#define TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_128 (4 << 28)
> +#define TEGRA_GPCDMA_MMIOSEQ_DATA_SWAP BIT(27)
> +#define TEGRA_GPCDMA_MMIOSEQ_BURST_1 (0 << 23)
> +#define TEGRA_GPCDMA_MMIOSEQ_BURST_2 (1 << 23)
> +#define TEGRA_GPCDMA_MMIOSEQ_BURST_4 (3 << 23)
> +#define TEGRA_GPCDMA_MMIOSEQ_BURST_8 (7 << 23)
> +#define TEGRA_GPCDMA_MMIOSEQ_BURST_16 (15 << 23)
> +#define TEGRA_GPCDMA_MMIOSEQ_MASTER_ID_SHIFT 19
> +#define TEGRA_GPCDMA_MMIOSEQ_WRAP_WORD_SHIFT 16
> +#define TEGRA_GPCDMA_MMIOSEQ_MMIO_PROT_SHIFT 7
> +
> +/* Channel WCOUNT */
> +#define TEGRA_GPCDMA_CHAN_WCOUNT 0x20
> +
> +/* Transfer count */
> +#define TEGRA_GPCDMA_CHAN_XFER_COUNT 0x24
> +
> +/* DMA byte count status */
> +#define TEGRA_GPCDMA_CHAN_DMA_BYTE_STATUS 0x28
> +
> +/* Error Status Register */
> +#define TEGRA_GPCDMA_CHAN_ERR_STATUS 0x30
> +#define TEGRA_GPCDMA_CHAN_ERR_TYPE_SHIFT (8)
> +#define TEGRA_GPCDMA_CHAN_ERR_TYPE_MASK (0xF)
> +#define TEGRA_GPCDMA_CHAN_ERR_TYPE(err) ( \
> + ((err) >> TEGRA_GPCDMA_CHAN_ERR_TYPE_SHIFT) & \
> + TEGRA_GPCDMA_CHAN_ERR_TYPE_MASK)
> +#define TEGRA_DMA_BM_FIFO_FULL_ERR (0xF)
> +#define TEGRA_DMA_PERIPH_FIFO_FULL_ERR (0xE)
> +#define TEGRA_DMA_PERIPH_ID_ERR (0xD)
> +#define TEGRA_DMA_STREAM_ID_ERR (0xC)
> +#define TEGRA_DMA_MC_SLAVE_ERR (0xB)
> +#define TEGRA_DMA_MMIO_SLAVE_ERR (0xA)
> +
> +/* Fixed Pattern */
> +#define TEGRA_GPCDMA_CHAN_FIXED_PATTERN 0x34
> +
> +#define TEGRA_GPCDMA_CHAN_TZ 0x38
> +#define TEGRA_GPCDMA_CHAN_TZ_MMIO_PROT_1 BIT(0)
> +#define TEGRA_GPCDMA_CHAN_TZ_MC_PROT_1 BIT(1)
> +
> +#define TEGRA_GPCDMA_CHAN_SPARE 0x3c
> +#define TEGRA_GPCDMA_CHAN_SPARE_EN_LEGACY_FC BIT(16)
> +
> +/*
> + * If any burst is in flight and DMA paused then this is the time to complete
> + * on-flight burst and update DMA status register.
> + */
> +#define TEGRA_GPCDMA_BURST_COMPLETE_TIME 20
> +#define TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT 100
> +
> +/* Channel base address offset from GPCDMA base address */
> +#define TEGRA_GPCDMA_CHANNEL_BASE_ADD_OFFSET 0x10000
> +
> +struct tegra_dma;
> +
> +/*
> + * tegra_dma_chip_data Tegra chip specific DMA data
> + * @nr_channels: Number of channels available in the controller.
> + * @channel_reg_size: Channel register size.
> + * @max_dma_count: Maximum DMA transfer count supported by DMA controller.
> + * @hw_support_pause: DMA HW engine support pause of the channel.
> + */
> +struct tegra_dma_chip_data {
> + int nr_channels;
> + int channel_reg_size;
> + int max_dma_count;
> + bool hw_support_pause;
> +};
> +
> +/* DMA channel registers */
> +struct tegra_dma_channel_regs {
> + unsigned long csr;
> + unsigned long src_ptr;
> + unsigned long dst_ptr;
> + unsigned long high_addr_ptr;
> + unsigned long mc_seq;
> + unsigned long mmio_seq;
> + unsigned long wcount;
> + unsigned long fixed_pattern;
> +};
> +
> +/*
> + * tegra_dma_sg_req: Dma request details to configure hardware. This
> + * contains the details for one transfer to configure DMA hw.
> + * The client's request for data transfer can be broken into multiple
> + * sub-transfer as per requester details and hw support.
> + * This sub transfer get added in the list of transfer and point to Tegra
> + * DMA descriptor which manages the transfer details.
> + */
> +struct tegra_dma_sg_req {
> + struct tegra_dma_channel_regs ch_regs;
> + int req_len;
> + bool configured;
> + bool skipped;
> + bool last_sg;
> + bool half_done;
> + struct list_head node;
> + struct tegra_dma_desc *dma_desc;
> +};
> +
> +/*
> + * tegra_dma_desc: Tegra DMA descriptors which manages the client requests.
> + * This descriptor keep track of transfer status, callbacks and request
> + * counts etc.
> + */
> +struct tegra_dma_desc {
> + struct virt_dma_desc vd;
> + int bytes_requested;
> + int bytes_transferred;
> + struct tegra_dma_channel *tdc;
> +};
> +
> +struct tegra_dma_channel;
> +
> +typedef void (*dma_isr_handler)(struct tegra_dma_channel *tdc,
> + bool to_terminate);
> +
> +/* tegra_dma_channel: Channel specific information */

What about to use proper kernel-doc style formatting?

> +struct tegra_dma_channel {
> + struct virt_dma_chan vc;
> + struct tegra_dma_desc *dma_desc;
> + struct tegra_dma_desc *pending_dma_desc;
> + char name[30];
> + bool config_init;
> + int id;
> + int irq;
> + unsigned long chan_base_offset;
> + raw_spinlock_t lock;
> + bool busy;
> + bool is_pending;
> + struct tegra_dma *tdma;
> +
> + /* List for managing pending sg requests */
> + struct list_head pending_sg_req;
> +
> + /* ISR handler and tasklet for bottom half of isr handling */
> + dma_isr_handler isr_handler;
> +
> + /* Channel-slave specific configuration */
> + int slave_id;
> + struct dma_slave_config dma_sconfig;
> + struct tegra_dma_channel_regs channel_reg;
> +};
> +
> +/* tegra_dma: Tegra DMA specific information */
> +struct tegra_dma {
> + struct dma_device dma_dev;
> + struct device *dev;
> + void __iomem *base_addr;
> + const struct tegra_dma_chip_data *chip_data;
> + struct reset_control *rst;
> + /* Last member of the structure */
> + struct tegra_dma_channel channels[0];
> +};
> +
> +static inline void tdc_write(struct tegra_dma_channel *tdc,
> + u32 reg, u32 val)
> +{
> + writel(val, tdc->tdma->base_addr + tdc->chan_base_offset + reg);

writel_relaxed()

> +}
> +
> +static inline u32 tdc_read(struct tegra_dma_channel *tdc, u32 reg)
> +{
> + return readl(tdc->tdma->base_addr + tdc->chan_base_offset + reg);

readl_relaxed()

> +}
> +
> +static inline struct tegra_dma_channel *to_tegra_dma_chan(struct dma_chan *dc)
> +{
> + return container_of(dc, struct tegra_dma_channel, vc.chan);
> +}
> +
> +static inline struct tegra_dma_desc *vd_to_tegra_dma_desc(
> + struct virt_dma_desc *vd)
> +{
> + return container_of(vd, struct tegra_dma_desc, vd);
> +}
> +
> +static inline struct device *tdc2dev(struct tegra_dma_channel *tdc)
> +{
> + return tdc->vc.chan.device->dev;
> +}
> +
> +static void tegra_dma_dump_chan_regs(struct tegra_dma_channel *tdc)
> +{
> + pr_info("DMA Channel %d name %s register dump:\n",
> + tdc->id, tdc->name);
> + pr_info("CSR %x STA %x CSRE %x SRC %x DST %x\n",
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSR),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSRE),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_DST_PTR)
> + );
> + pr_info("MCSEQ %x IOSEQ %x WCNT %x XFER %x BSTA %x\n",
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_WCOUNT),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT),
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_DMA_BYTE_STATUS)
> + );
> + pr_info("DMA ERR_STA %x\n",
> + tdc_read(tdc, TEGRA_GPCDMA_CHAN_ERR_STATUS));
> +}
> +
> +static void tegra_dma_desc_free(struct virt_dma_desc *vd)
> +{
> + struct tegra_dma_desc *dma_desc = vd_to_tegra_dma_desc(vd);
> + unsigned long flags;
> +
> + if (!dma_desc)
> + return;
> + raw_spin_lock_irqsave(&dma_desc->tdc->lock, flags);
> + kfree(dma_desc);

> + raw_spin_unlock_irqrestore(&dma_desc->tdc->lock, flags);
> + dma_desc->tdc = NULL;

use-after-free

> +}
> +
> +static int tegra_dma_slave_config(struct dma_chan *dc,
> + struct dma_slave_config *sconfig)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> +
> + if (!list_empty(&tdc->pending_sg_req)) {
> + dev_err(tdc2dev(tdc), "Configuration not allowed\n");
> + return -EBUSY;
> + }
> +
> + memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig));
> + if (tdc->slave_id == -1)
> + tdc->slave_id = sconfig->slave_id;
> + tdc->config_init = true;
> + return 0;
> +}
> +
> +static int tegra_dma_pause(struct tegra_dma_channel *tdc)
> +{
> + int timeout = TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT;
> +
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSRE, TEGRA_GPCDMA_CHAN_CSRE_PAUSE);
> +
> + /* Wait until busy bit is de-asserted */
> + do {
> + if (!(tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS) &
> + TEGRA_GPCDMA_STATUS_BUSY))
> + break;
> + udelay(TEGRA_GPCDMA_BURST_COMPLETE_TIME);
> + timeout -= TEGRA_GPCDMA_BURST_COMPLETE_TIME;
> + } while (timeout);

readl_relaxed_poll_timeout_atomic()

> + if (!timeout) {
> + dev_err(tdc2dev(tdc), "DMA pause timed out\n");
> + return -ETIMEDOUT;
> + }
> +
> + return 0;
> +}
> +
> +static void tegra_dma_stop(struct tegra_dma_channel *tdc)
> +{
> + u32 csr;
> + u32 status;

u32 csr, status;

> + /* Disable interrupts */
> + csr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSR);
> + csr &= ~TEGRA_GPCDMA_CSR_IE_EOC;
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR, csr);
> +
> + /* Disable DMA */
> + csr &= ~TEGRA_GPCDMA_CSR_ENB;
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR, csr);

Couldn't these CSR writes be merged?

> + /* Clear interrupt status if it is there */
> + status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> + if (status & TEGRA_GPCDMA_STATUS_ISE_EOC) {
> + dev_dbg(tdc2dev(tdc), "%s():clearing interrupt\n", __func__);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_STATUS, status);
> + }
> + tdc->busy = false;
> +}
> +
> +static void tegra_dma_start(struct tegra_dma_channel *tdc,
> + struct tegra_dma_sg_req *sg_req)
> +{
> + struct tegra_dma_channel_regs *ch_regs = &sg_req->ch_regs;
> +
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_WCOUNT, ch_regs->wcount);
> +
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR, 0);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR, ch_regs->src_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_DST_PTR, ch_regs->dst_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR, ch_regs->high_addr_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_FIXED_PATTERN, ch_regs->fixed_pattern);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ, ch_regs->mmio_seq);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MCSEQ, ch_regs->mc_seq);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSRE, 0);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR, ch_regs->csr);
> +
> + /* Start DMA */
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR,
> + ch_regs->csr | TEGRA_GPCDMA_CSR_ENB);
> +}
> +
> +static void tdc_start_head_req(struct tegra_dma_channel *tdc)
> +{
> + struct tegra_dma_sg_req *sg_req;
> + struct virt_dma_desc *vdesc;
> +
> + if (list_empty(&tdc->pending_sg_req))
> + return;
> +
> + if (tdc->is_pending)
> + return;
> +
> + vdesc = vchan_next_desc(&tdc->vc);
> + if (!vdesc)
> + return;
> + list_del(&vdesc->node);
> + tdc->dma_desc = vd_to_tegra_dma_desc(vdesc);
> + tdc->is_pending = true;
> + tdc->dma_desc->tdc = tdc;
> + sg_req = list_first_entry(&tdc->pending_sg_req,
> + typeof(*sg_req), node);
> + tegra_dma_start(tdc, sg_req);
> + sg_req->configured = true;
> + sg_req->skipped = false;
> + tdc->busy = true;
> +}
> +
> +static void tegra_dma_abort_all(struct tegra_dma_channel *tdc)
> +{
> + struct tegra_dma_sg_req *sgreq;
> +
> + while (!list_empty(&tdc->pending_sg_req)) {
> + sgreq = list_first_entry(&tdc->pending_sg_req,
> + typeof(*sgreq), node);
> + list_del(&sgreq->node);
> + kfree(sgreq);
> + }
> + tdc->isr_handler = NULL;
> +}
> +
> +static void handle_once_dma_done(struct tegra_dma_channel *tdc,
> + bool to_terminate)
> +{
> + struct tegra_dma_sg_req *sgreq;
> + struct tegra_dma_desc *dma_desc;
> +
> + tdc->busy = false;
> + sgreq = list_first_entry(&tdc->pending_sg_req, typeof(*sgreq), node);
> + dma_desc = sgreq->dma_desc;
> + dma_desc->bytes_transferred += sgreq->req_len;
> +
> + if (sgreq->last_sg) {
> + vchan_cookie_complete(&tdc->dma_desc->vd);
> + tdc->is_pending = false;
> + tdc->dma_desc = NULL;
> + }
> + list_del(&sgreq->node);
> + kfree(sgreq);
> +
> + if (to_terminate || list_empty(&tdc->pending_sg_req))
> + return;
> +
> + tdc_start_head_req(tdc);
> +}
> +
> +static void tegra_dma_chan_decode_error(struct tegra_dma_channel *tdc,
> + unsigned int err_status)
> +{
> + switch (TEGRA_GPCDMA_CHAN_ERR_TYPE(err_status)) {
> + case TEGRA_DMA_BM_FIFO_FULL_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d bm fifo full\n", tdc->id);
> + break;
> +
> + case TEGRA_DMA_PERIPH_FIFO_FULL_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d peripheral fifo full\n", tdc->id);
> + break;
> +
> + case TEGRA_DMA_PERIPH_ID_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d illegal peripheral id\n", tdc->id);
> + break;
> +
> + case TEGRA_DMA_STREAM_ID_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d illegal stream id\n", tdc->id);
> + break;
> +
> + case TEGRA_DMA_MC_SLAVE_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d mc slave error\n", tdc->id);
> + break;
> +
> + case TEGRA_DMA_MMIO_SLAVE_ERR:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d mmio slave error\n", tdc->id);
> + break;
> +
> + default:
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d security violation %x\n", tdc->id,
> + err_status);
> + }
> +}
> +
> +static irqreturn_t tegra_dma_isr(int irq, void *dev_id)
> +{
> + struct tegra_dma_channel *tdc = dev_id;
> + unsigned long status;
> + unsigned long flags;
> + unsigned int err_status;
> +
> + raw_spin_lock_irqsave(&tdc->lock, flags);

There is no need to save-restore interrupt context in ISR because
interrupt is disabled.

> + status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> + err_status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_ERR_STATUS);
> +
> + if (err_status) {
> + tegra_dma_chan_decode_error(tdc, err_status);
> + tegra_dma_dump_chan_regs(tdc);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_ERR_STATUS, 0xFFFFFFFF);
> + }
> +
> + if (status & TEGRA_GPCDMA_STATUS_ISE_EOC) {
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_STATUS,
> + TEGRA_GPCDMA_STATUS_ISE_EOC);
> + if (tdc->isr_handler)
> + tdc->isr_handler(tdc, false);
> + else {
> + dev_err(tdc->tdma->dev,
> + "GPCDMA CH%d: status %lx ISR handler absent!\n",
> + tdc->id, status);
> + tegra_dma_dump_chan_regs(tdc);
> + }
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return IRQ_HANDLED;
> + }
> +
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return IRQ_NONE;
> +}
> +
> +static void tegra_dma_issue_pending(struct dma_chan *dc)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + unsigned long flags;
> +
> + raw_spin_lock_irqsave(&tdc->lock, flags);
> + if (list_empty(&tdc->pending_sg_req)) {
> + dev_err(tdc2dev(tdc), "No DMA request\n");
> + goto end;
> + }
> +
> + if (!tdc->busy)
> + if (vchan_issue_pending(&tdc->vc))
> + tdc_start_head_req(tdc);
> +
> +end:
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> +}
> +
> +static void tegra_dma_reset_client(struct tegra_dma_channel *tdc)
> +{
> + uint32_t csr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSR);
> +
> + csr &= ~(TEGRA_GPCDMA_CSR_REQ_SEL_MASK <<
> + TEGRA_GPCDMA_CSR_REQ_SEL_SHIFT);
> + csr |= (TEGRA_GPCDMA_CSR_REQ_SEL_UNUSED
> + << TEGRA_GPCDMA_CSR_REQ_SEL_SHIFT);

Use FIELD_GET and FIELD_PREP macros. Same for all other similar
occurences in the code.

> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR, csr);
> +}
> +
> +static int tegra_dma_terminate_all(struct dma_chan *dc)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct tegra_dma_sg_req *sgreq;
> + unsigned long flags;
> + unsigned long status, burst_time;
> + unsigned long wcount = 0;
> + bool was_busy;
> + int err;
> +
> + raw_spin_lock_irqsave(&tdc->lock, flags);
> + if (list_empty(&tdc->pending_sg_req)) {
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return 0;
> + }
> +
> + if (!tdc->busy)
> + goto skip_dma_stop;
> +
> + if (tdc->tdma->chip_data->hw_support_pause) {
> + err = tegra_dma_pause(tdc);
> + if (err) {
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return err;
> + }
> + } else {
> + /* Before Reading DMA status to figure out number
> + * of bytes transferred by DMA channel:
> + * Change the client associated with the DMA channel
> + * to stop DMA engine from starting any more bursts for
> + * the given client and wait for in flight bursts to complete
> + */
> + tegra_dma_reset_client(tdc);
> +
> + /* Wait for in flight data transfer to finish */
> + udelay(TEGRA_GPCDMA_BURST_COMPLETE_TIME);
> +
> + /* If TX/RX path is still active wait till it becomes
> + * inactive
> + */
> + burst_time = 0;
> + while (burst_time < TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT) {
> + status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> + if (status & (TEGRA_GPCDMA_STATUS_CHANNEL_TX |
> + TEGRA_GPCDMA_STATUS_CHANNEL_RX)) {
> + udelay(5);
> + burst_time += 5;
> + } else
> + break;

Wrong coding style, please use 'scripts/checkpatch.pl --strict ...' and
fix all the reported problems.

> + }

readx_poll_timeout_atomic()?

> + if (burst_time >= TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT) {
> + pr_err("Timeout waiting for DMA burst completion!\n");
> + tegra_dma_dump_chan_regs(tdc);
> + }
> + }
> +
> + status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> + wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT);
> + if (status & TEGRA_GPCDMA_STATUS_ISE_EOC) {
> + dev_dbg(tdc2dev(tdc), "%s():handling isr\n", __func__);
> + tdc->isr_handler(tdc, true);
> + status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> + wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT);
> + }
> +
> + was_busy = tdc->busy;
> + tegra_dma_stop(tdc);
> +
> + if (!list_empty(&tdc->pending_sg_req) && was_busy) {
> + sgreq = list_first_entry(&tdc->pending_sg_req,
> + typeof(*sgreq), node);
> + sgreq->dma_desc->bytes_transferred +=
> + sgreq->req_len - (wcount * 4);
> + }
> +
> +skip_dma_stop:
> + tegra_dma_abort_all(tdc);
> + vchan_free_chan_resources(&tdc->vc);
> + if (tdc->is_pending) {
> + tdc->pending_dma_desc = tdc->dma_desc;
> + tdc->is_pending = false;
> + tdc->dma_desc = NULL;
> + }
> +
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return 0;
> +}
> +
> +static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
> + dma_cookie_t cookie, struct dma_tx_state *txstate)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct tegra_dma_desc *dma_desc;
> + struct tegra_dma_sg_req *sg_req;
> + enum dma_status ret;
> + unsigned long flags;
> + unsigned int residual;
> +
> + raw_spin_lock_irqsave(&tdc->lock, flags);
> +
> + ret = dma_cookie_status(dc, cookie, txstate);
> + if (ret == DMA_COMPLETE) {
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return ret;
> + }
> +
> + /* Check on pending dma desc*/
> + if(tdc->pending_dma_desc) {
> + dma_desc = tdc->pending_dma_desc;
> + tdc->pending_dma_desc = NULL;

So any tegra_dma_tx_status() invocation kills the tdc->pending_dma_desc?
This doesn't look right.

> + if (dma_desc->vd.tx.cookie == cookie) {
> + residual = dma_desc->bytes_requested -
> + (dma_desc->bytes_transferred %
> + dma_desc->bytes_requested);
> + dma_set_residue(txstate, residual);
> + kfree(dma_desc);
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return ret;
> + }
> + }
> +
> + /* Check in pending list */
> + list_for_each_entry(sg_req, &tdc->pending_sg_req, node) {
> + dma_desc = sg_req->dma_desc;
> + if (dma_desc->vd.tx.cookie == cookie) {
> + residual = dma_desc->bytes_requested -
> + (dma_desc->bytes_transferred %
> + dma_desc->bytes_requested);
> + dma_set_residue(txstate, residual);
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return ret;
> + }
> + }

What about to support DMA_RESIDUE_GRANULARITY_BURST? See tegra20-apb-dma
for an example.

> + dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie);
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> + return ret;
> +}
> +
> +static inline int get_bus_width(struct tegra_dma_channel *tdc,
> + enum dma_slave_buswidth slave_bw)
> +{
> + switch (slave_bw) {
> + case DMA_SLAVE_BUSWIDTH_1_BYTE:
> + return TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_8;
> + case DMA_SLAVE_BUSWIDTH_2_BYTES:
> + return TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_16;
> + case DMA_SLAVE_BUSWIDTH_4_BYTES:
> + return TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_32;
> + case DMA_SLAVE_BUSWIDTH_8_BYTES:
> + return TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_64;
> + default:
> + dev_warn(tdc2dev(tdc),
> + "slave bw is not supported, using 32bits\n");
> + return TEGRA_GPCDMA_MMIOSEQ_BUS_WIDTH_32;
> + }
> +}
> +
> +static inline int get_burst_size(struct tegra_dma_channel *tdc,
> + u32 burst_size, enum dma_slave_buswidth slave_bw, int len)
> +{
> + int burst_byte;
> + int burst_mmio_width;
> +
> + /*
> + * burst_size from client is in terms of the bus_width.
> + * convert that into words.
> + */
> + burst_byte = burst_size * slave_bw;
> + burst_mmio_width = burst_byte / 4;
> +
> + /* If burst size is 0 then calculate the burst size based on length */
> + if (!burst_mmio_width) {
> + if (len & 0xF)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_1;
> + else if ((len >> 3) & 0x1)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_2;
> + else if ((len >> 4) & 0x1)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_4;
> + else if ((len >> 5) & 0x1)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_8;
> + else
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_16;
> + }
> + if (burst_mmio_width < 2)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_1;
> + else if (burst_mmio_width < 4)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_2;
> + else if (burst_mmio_width < 8)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_4;
> + else if (burst_mmio_width < 16)
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_8;
> + else
> + return TEGRA_GPCDMA_MMIOSEQ_BURST_16;
> +}
> +
> +static int get_transfer_param(struct tegra_dma_channel *tdc,
> + enum dma_transfer_direction direction, unsigned long *apb_addr,
> + unsigned long *mmio_seq, unsigned long *csr, unsigned int *burst_size,
> + enum dma_slave_buswidth *slave_bw)
> +{
> +
> + switch (direction) {
> + case DMA_MEM_TO_DEV:
> + *apb_addr = tdc->dma_sconfig.dst_addr;
> + *mmio_seq = get_bus_width(tdc, tdc->dma_sconfig.dst_addr_width);
> + *burst_size = tdc->dma_sconfig.dst_maxburst;
> + *slave_bw = tdc->dma_sconfig.dst_addr_width;
> + *csr = TEGRA_GPCDMA_CSR_DMA_MEM2IO_FC;
> + return 0;
> +
> + case DMA_DEV_TO_MEM:
> + *apb_addr = tdc->dma_sconfig.src_addr;
> + *mmio_seq = get_bus_width(tdc, tdc->dma_sconfig.src_addr_width);
> + *burst_size = tdc->dma_sconfig.src_maxburst;
> + *slave_bw = tdc->dma_sconfig.src_addr_width;
> + *csr = TEGRA_GPCDMA_CSR_DMA_IO2MEM_FC;
> + return 0;
> + case DMA_MEM_TO_MEM:
> + *burst_size = tdc->dma_sconfig.src_addr_width;
> + *csr = TEGRA_GPCDMA_CSR_DMA_MEM2MEM;
> + return 0;
> + default:
> + dev_err(tdc2dev(tdc), "Dma direction is not supported\n");
> + return -EINVAL;
> + }
> + return -EINVAL;
> +}
> +
> +static struct dma_async_tx_descriptor *tegra_dma_prep_dma_memset(
> + struct dma_chan *dc, dma_addr_t dest, int value, size_t len,
> + unsigned long flags)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct tegra_dma_desc *dma_desc;
> + struct list_head req_list;
> + struct tegra_dma_sg_req *sg_req = NULL;
> + unsigned long csr, mc_seq;
> +
> + INIT_LIST_HEAD(&req_list);
> + /* Set dma mode to fixed pattern */
> + csr = TEGRA_GPCDMA_CSR_DMA_FIXED_PAT;
> + /* Enable once or continuous mode */
> + csr |= TEGRA_GPCDMA_CSR_ONCE;
> + /* Enable IRQ mask */
> + csr |= TEGRA_GPCDMA_CSR_IRQ_MASK;
> + /* Enable the dma interrupt */
> + if (flags & DMA_PREP_INTERRUPT)
> + csr |= TEGRA_GPCDMA_CSR_IE_EOC;
> + /* Configure default priority weight for the channel */
> + csr |= (1 << TEGRA_GPCDMA_CSR_WEIGHT_SHIFT);
> +
> + mc_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
> + /* retain stream-id and clean rest */
> + mc_seq &= (TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT);
> +
> + /* Set the address wrapping */
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP0_SHIFT;
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP1_SHIFT;
> +
> + /* Program outstanding MC requests */
> + mc_seq |= (1 << TEGRA_GPCDMA_MCSEQ_REQ_COUNT_SHIFT);
> + /* Set burst size */
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_BURST_16;
> +
> + dma_desc = kzalloc(sizeof(struct tegra_dma_desc), GFP_NOWAIT);
> + if (!dma_desc) {
> + dev_err(tdc2dev(tdc), "Dma descriptors not available\n");
> + return NULL;
> + }
> + dma_desc->bytes_requested = 0;
> + dma_desc->bytes_transferred = 0;
> +
> + if ((len & 3) || (dest & 3) ||
> + (len > tdc->tdma->chip_data->max_dma_count)) {
> + dev_err(tdc2dev(tdc),
> + "Dma length/memory address is not supported\n");
> + kfree(dma_desc);
> + return NULL;
> + }
> +
> + sg_req = kzalloc(sizeof(struct tegra_dma_sg_req), GFP_NOWAIT);
> + if (!sg_req) {
> + dev_err(tdc2dev(tdc), "Dma sg-req not available\n");
> + kfree(dma_desc);
> + return NULL;
> + }
> +
> + dma_desc->bytes_requested += len;
> + sg_req->ch_regs.src_ptr = 0;
> + sg_req->ch_regs.dst_ptr = dest;
> + sg_req->ch_regs.high_addr_ptr = ((dest >> 32) &
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_MASK) <<
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_SHIFT;
> + sg_req->ch_regs.fixed_pattern = value;
> + /* Word count reg takes value as (N +1) words */
> + sg_req->ch_regs.wcount = ((len - 4) >> 2);
> + sg_req->ch_regs.csr = csr;
> + sg_req->ch_regs.mmio_seq = 0;
> + sg_req->ch_regs.mc_seq = mc_seq;
> + sg_req->configured = false;
> + sg_req->skipped = false;
> + sg_req->last_sg = false;
> + sg_req->dma_desc = dma_desc;
> + sg_req->req_len = len;
> + sg_req->last_sg = true;
> +
> + list_add_tail(&sg_req->node, &tdc->pending_sg_req);
> +
> + if (!tdc->isr_handler)
> + tdc->isr_handler = handle_once_dma_done;
> +
> + tdc->pending_dma_desc = NULL;
> +
> + return vchan_tx_prep(&tdc->vc, &dma_desc->vd, flags);
> +}
> +
> +static struct dma_async_tx_descriptor *tegra_dma_prep_dma_memcpy(
> + struct dma_chan *dc, dma_addr_t dest, dma_addr_t src, size_t len,
> + unsigned long flags)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct tegra_dma_desc *dma_desc;
> + struct list_head req_list;
> + struct tegra_dma_sg_req *sg_req = NULL;
> + unsigned long csr, mc_seq;
> +
> + INIT_LIST_HEAD(&req_list);
> + /* Set dma mode to memory to memory transfer */
> + csr = TEGRA_GPCDMA_CSR_DMA_MEM2MEM;
> + /* Enable once or continuous mode */
> + csr |= TEGRA_GPCDMA_CSR_ONCE;
> + /* Enable IRQ mask */
> + csr |= TEGRA_GPCDMA_CSR_IRQ_MASK;
> + /* Enable the dma interrupt */
> + if (flags & DMA_PREP_INTERRUPT)
> + csr |= TEGRA_GPCDMA_CSR_IE_EOC;
> + /* Configure default priority weight for the channel */
> + csr |= (1 << TEGRA_GPCDMA_CSR_WEIGHT_SHIFT);
> +
> + mc_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
> + /* retain stream-id and clean rest */
> + mc_seq &= ((TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT) |
> + (TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID1_SHIFT));
> +
> + /* Set the address wrapping */
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP0_SHIFT;
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP1_SHIFT;
> +
> + /* Program outstanding MC requests */
> + mc_seq |= (1 << TEGRA_GPCDMA_MCSEQ_REQ_COUNT_SHIFT);
> + /* Set burst size */
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_BURST_16;
> +
> + dma_desc = kzalloc(sizeof(struct tegra_dma_desc), GFP_NOWAIT);
> + if (!dma_desc) {
> + dev_err(tdc2dev(tdc), "Dma descriptors not available\n");
> + return NULL;
> + }
> +
> + dma_desc->bytes_requested = 0;
> + dma_desc->bytes_transferred = 0;
> +
> + if ((len & 3) || (src & 3) || (dest & 3) ||
> + (len > tdc->tdma->chip_data->max_dma_count)) {
> + dev_err(tdc2dev(tdc),
> + "Dma length/memory address is not supported\n");
> + kfree(dma_desc);
> + return NULL;
> + }
> +
> + sg_req = kzalloc(sizeof(struct tegra_dma_sg_req), GFP_NOWAIT);
> + if (!sg_req) {
> + dev_err(tdc2dev(tdc), "Dma sg-req not available\n");
> + kfree(dma_desc);
> + return NULL;
> + }
> +
> + dma_desc->bytes_requested += len;
> + sg_req->ch_regs.src_ptr = src;
> + sg_req->ch_regs.dst_ptr = dest;
> + sg_req->ch_regs.high_addr_ptr = (src >> 32) &
> + TEGRA_GPCDMA_HIGH_ADDR_SCR_PTR_MASK;
> + sg_req->ch_regs.high_addr_ptr |= ((dest >> 32) &
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_MASK) <<
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_SHIFT;
> + /* Word count reg takes value as (N +1) words */
> + sg_req->ch_regs.wcount = ((len - 4) >> 2);
> + sg_req->ch_regs.csr = csr;
> + sg_req->ch_regs.mmio_seq = 0;
> + sg_req->ch_regs.mc_seq = mc_seq;
> + sg_req->configured = false;
> + sg_req->skipped = false;
> + sg_req->last_sg = false;
> + sg_req->dma_desc = dma_desc;
> + sg_req->req_len = len;
> + sg_req->last_sg = true;
> +
> + list_add_tail(&sg_req->node, &tdc->pending_sg_req);
> +
> + if (!tdc->isr_handler)
> + tdc->isr_handler = handle_once_dma_done;
> +
> + tdc->pending_dma_desc = NULL;
> +
> + return vchan_tx_prep(&tdc->vc, &dma_desc->vd, flags);
> +}
> +
> +static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
> + struct dma_chan *dc, struct scatterlist *sgl, unsigned int sg_len,
> + enum dma_transfer_direction direction, unsigned long flags,
> + void *context)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct tegra_dma_desc *dma_desc;
> + unsigned int i;
> + struct scatterlist *sg;
> + unsigned long csr, mc_seq, apb_ptr = 0, mmio_seq = 0;
> + struct list_head req_list;
> + struct tegra_dma_sg_req *sg_req = NULL;
> + u32 burst_size;
> + enum dma_slave_buswidth slave_bw = 0;

Please don't iunitialize varaibles where it's not necessary. Same for
all other occurences in the code.

> + int ret;

You could make these definitions to look nicer, and thus easier to read,
by changing the order like this:

struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
unsigned long csr, mc_seq, apb_ptr = 0, mmio_seq = 0;
struct tegra_dma_sg_req *sg_req = NULL;
enum dma_slave_buswidth slave_bw;
struct tegra_dma_desc *dma_desc;
struct list_head req_list;
struct scatterlist *sg;
u32 burst_size;
unsigned int i;
int ret;

Same for all other similar occurences in the code.

> + if (!tdc->config_init) {
> + dev_err(tdc2dev(tdc), "dma channel is not configured\n");
> + return NULL;
> + }
> + if (sg_len < 1) {
> + dev_err(tdc2dev(tdc), "Invalid segment length %d\n", sg_len);
> + return NULL;
> + }
> +
> + ret = get_transfer_param(tdc, direction, &apb_ptr, &mmio_seq, &csr,
> + &burst_size, &slave_bw);
> + if (ret < 0)
> + return NULL;
> +
> + INIT_LIST_HEAD(&req_list);
> +
> + /* Enable once or continuous mode */
> + csr |= TEGRA_GPCDMA_CSR_ONCE;
> + /* Program the slave id in requestor select */
> + csr |= tdc->slave_id << TEGRA_GPCDMA_CSR_REQ_SEL_SHIFT;
> + /* Enable IRQ mask */
> + csr |= TEGRA_GPCDMA_CSR_IRQ_MASK;
> + /* Configure default priority weight for the channel*/
> + csr |= (1 << TEGRA_GPCDMA_CSR_WEIGHT_SHIFT);
> +
> + /* Enable the dma interrupt */
> + if (flags & DMA_PREP_INTERRUPT)
> + csr |= TEGRA_GPCDMA_CSR_IE_EOC;
> +
> + mc_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
> + /* retain stream-id and clean rest */
> + mc_seq &= (TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT);
> +
> + /* Set the address wrapping on both MC and MMIO side */
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP0_SHIFT;
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_WRAP_NONE <<
> + TEGRA_GPCDMA_MCSEQ_WRAP1_SHIFT;
> + mmio_seq |= (1 << TEGRA_GPCDMA_MMIOSEQ_WRAP_WORD_SHIFT);
> +
> + /* Program 2 MC outstanding requests by default. */
> + mc_seq |= (1 << TEGRA_GPCDMA_MCSEQ_REQ_COUNT_SHIFT);
> +
> + /* Setting MC burst size depending on MMIO burst size */
> + if (burst_size == 64)
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_BURST_16;
> + else
> + mc_seq |= TEGRA_GPCDMA_MCSEQ_BURST_2;
> +
> + dma_desc = kzalloc(sizeof(struct tegra_dma_desc), GFP_NOWAIT);
> + if (!dma_desc) {
> + dev_err(tdc2dev(tdc), "Dma descriptors not available\n");
> + return NULL;
> + }
> +
> + dma_desc->bytes_requested = 0;
> + dma_desc->bytes_transferred = 0;
> +
> + /* Make transfer requests */
> + for_each_sg(sgl, sg, sg_len, i) {
> + u32 len;
> + dma_addr_t mem;
> +
> + mem = sg_dma_address(sg);
> + len = sg_dma_len(sg);
> +
> + if ((len & 3) || (mem & 3) ||
> + (len > tdc->tdma->chip_data->max_dma_count)) {
> + dev_err(tdc2dev(tdc),
> + "Dma length/memory address is not supported\n");
> + kfree(dma_desc);
> + return NULL;
> + }
> +
> + sg_req = kzalloc(sizeof(struct tegra_dma_sg_req), GFP_NOWAIT);
> + if (!sg_req) {
> + dev_err(tdc2dev(tdc), "Dma sg-req not available\n");
> + kfree(dma_desc);
> + goto sg_alloc_error;
> + }
> +
> + mmio_seq |= get_burst_size(tdc, burst_size, slave_bw, len);
> + dma_desc->bytes_requested += len;
> +
> + if (direction == DMA_MEM_TO_DEV) {
> + sg_req->ch_regs.src_ptr = mem;
> + sg_req->ch_regs.dst_ptr = apb_ptr;
> + sg_req->ch_regs.high_addr_ptr = (mem >> 32) &
> + TEGRA_GPCDMA_HIGH_ADDR_SCR_PTR_MASK;
> + } else if (direction == DMA_DEV_TO_MEM) {
> + sg_req->ch_regs.src_ptr = apb_ptr;
> + sg_req->ch_regs.dst_ptr = mem;
> + sg_req->ch_regs.high_addr_ptr = ((mem >> 32) &
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_MASK) <<
> + TEGRA_GPCDMA_HIGH_ADDR_DST_PTR_SHIFT;
> + }
> +
> + /*
> + * Word count register takes input in words. Writing a value
> + * of N into word count register means a req of (N+1) words.
> + */
> + sg_req->ch_regs.wcount = ((len - 4) >> 2);
> + sg_req->ch_regs.csr = csr;
> + sg_req->ch_regs.mmio_seq = mmio_seq;
> + sg_req->ch_regs.mc_seq = mc_seq;
> + sg_req->configured = false;
> + sg_req->skipped = false;
> + sg_req->last_sg = false;
> + sg_req->dma_desc = dma_desc;
> + sg_req->req_len = len;
> + list_add_tail(&sg_req->node, &tdc->pending_sg_req);
> + }
> + sg_req->last_sg = true;
> +
> + /*
> + * Make sure that mode should not be conflicting with currently
> + * configured mode.
> + */
> + if (!tdc->isr_handler)
> + tdc->isr_handler = handle_once_dma_done;
> +
> + tdc->pending_dma_desc = NULL;
> +
> + return vchan_tx_prep(&tdc->vc, &dma_desc->vd, flags);
> +
> +sg_alloc_error:
> + while (!list_empty(&tdc->pending_sg_req)) {
> + sg_req = list_first_entry(&tdc->pending_sg_req,
> + typeof(*sg_req), node);
> + list_del(&sg_req->node);
> + kfree(sg_req);
> + }
> + return NULL;
> +}
> +
> +static int tegra_dma_alloc_chan_resources(struct dma_chan *dc)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> +
> + dma_cookie_init(&tdc->vc.chan);
> + tdc->config_init = false;
> + return 0;
> +}
> +
> +static void tegra_dma_free_chan_resources(struct dma_chan *dc)
> +{
> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> + struct list_head sg_req_list;
> + unsigned long flags;
> +
> + INIT_LIST_HEAD(&sg_req_list);
> +
> + dev_dbg(tdc2dev(tdc), "Freeing channel %d\n", tdc->id);
> +
> + if (tdc->busy)
> + tegra_dma_terminate_all(dc);
> +
> + tasklet_kill(&tdc->vc.task);
> + raw_spin_lock_irqsave(&tdc->lock, flags);
> + tdc->pending_dma_desc = NULL;
> + list_splice_init(&tdc->pending_sg_req, &sg_req_list);
> + tdc->config_init = false;
> + tdc->isr_handler = NULL;
> + tdc->slave_id = -1;
> + raw_spin_unlock_irqrestore(&tdc->lock, flags);
> +}
> +
> +static struct dma_chan *tegra_dma_of_xlate(struct of_phandle_args *dma_spec,
> + struct of_dma *ofdma)
> +{
> + struct tegra_dma *tdma = ofdma->of_dma_data;
> + struct dma_chan *chan;
> + struct tegra_dma_channel *tdc;
> +
> + chan = dma_get_any_slave_channel(&tdma->dma_dev);
> + if (!chan)
> + return NULL;
> +
> + tdc = to_tegra_dma_chan(chan);
> + tdc->slave_id = dma_spec->args[0];
> +
> + return chan;
> +}
> +
> +static const struct tegra_dma_chip_data tegra186_dma_chip_data = {
> + .nr_channels = 32,
> + .channel_reg_size = 0x10000,
> + .max_dma_count = 1024UL * 1024UL * 1024UL,
> + .hw_support_pause = false,
> +};
> +
> +static const struct tegra_dma_chip_data tegra194_dma_chip_data = {
> + .nr_channels = 32,
> + .channel_reg_size = 0x10000,

SZ_64K

Same for tegra186 above.

> + .max_dma_count = 1024UL * 1024UL * 1024UL,

SZ_1G

Same for tegra186 above.

> + .hw_support_pause = true,
> +};
> +
> +static const struct of_device_id tegra_dma_of_match[] = {
> + {
> + .compatible = "nvidia,tegra186-gpcdma",
> + .data = &tegra186_dma_chip_data,
> + }, {
> + .compatible = "nvidia,tegra194-gpcdma",
> + .data = &tegra194_dma_chip_data,
> + }, {
> + },
> +};
> +MODULE_DEVICE_TABLE(of, tegra_dma_of_match);
> +
> +static int tegra_dma_program_sid(struct tegra_dma_channel *tdc,
> + int chan, int stream_id)
> +{
> + unsigned int reg_val = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
> +
> + reg_val &= ~(TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT);
> + reg_val &= ~(TEGRA_GPCDMA_MCSEQ_STREAM_ID_MASK <<
> + TEGRA_GPCDMA_MCSEQ_STREAM_ID1_SHIFT);
> +
> + reg_val |= (stream_id << TEGRA_GPCDMA_MCSEQ_STREAM_ID0_SHIFT);
> + reg_val |= (stream_id << TEGRA_GPCDMA_MCSEQ_STREAM_ID1_SHIFT);
> +
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MCSEQ, reg_val);
> + return 0;
> +}
> +
> +static int tegra_dma_probe(struct platform_device *pdev)
> +{
> + struct resource *res;
> + struct tegra_dma *tdma;
> + int ret;

> + int i;

unsigned int

> + const struct tegra_dma_chip_data *cdata = NULL;
> + struct tegra_dma_chip_data *chip_data = NULL;
> + int start_chan_idx = 0;

unsigned int

> + int nr_chans, stream_id;

unsigned int

Same for all similar occurences in the code. Don't use signed types
where sign isn't needed.

> + if (pdev->dev.of_node) {
> + const struct of_device_id *match;
> +
> + match = of_match_device(of_match_ptr(tegra_dma_of_match),
> + &pdev->dev);
> + if (!match) {
> + dev_err(&pdev->dev, "Error: No device match found\n");
> + return -ENODEV;
> + }
> + cdata = match->data;
> +
> + ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> + &nr_chans);
> + if (!ret) {
> + /* Allocate chip data and update number of channels */
> + chip_data =
> + devm_kzalloc(&pdev->dev,
> + sizeof(struct tegra_dma_chip_data),
> + GFP_KERNEL);
> + if (!chip_data) {
> + dev_err(&pdev->dev, "Error: memory allocation failed\n");
> + return -ENOMEM;
> + }
> + memcpy(chip_data, cdata,
> + sizeof(struct tegra_dma_chip_data));
> + chip_data->nr_channels = nr_chans;
> + cdata = chip_data;
> + }
> + ret = of_property_read_u32(pdev->dev.of_node,
> + "nvidia,start-dma-channel-index",
> + &start_chan_idx);
> + if (ret)
> + start_chan_idx = 0;
> +
> + ret = of_property_read_u32(pdev->dev.of_node,
> + "nvidia,stream-id", &stream_id);
> + if (ret)
> + stream_id = TEGRA186_SID_GPCDMA_0;
> +
> + } else {
> + /* If no device tree then fallback to chip data */
> + cdata =
> + (struct tegra_dma_chip_data *)pdev->id_entry->driver_data;
> + stream_id = TEGRA186_SID_GPCDMA_0;
> + }
> +
> + tdma = devm_kzalloc(&pdev->dev, sizeof(*tdma) + cdata->nr_channels *
> + sizeof(struct tegra_dma_channel), GFP_KERNEL);
> + if (!tdma)
> + return -ENOMEM;
> +
> + tdma->dev = &pdev->dev;
> + tdma->chip_data = cdata;
> + platform_set_drvdata(pdev, tdma);
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res) {
> + dev_err(&pdev->dev, "No mem resource for DMA\n");
> + return -EINVAL;
> + }
> +
> + tdma->base_addr = devm_ioremap_resource(&pdev->dev, res);

devm_platform_ioremap_resource()

> + if (IS_ERR(tdma->base_addr))
> + return PTR_ERR(tdma->base_addr);
> +
> + tdma->rst = devm_reset_control_get(&pdev->dev, "gpcdma");
> + if (IS_ERR(tdma->rst)) {
> + dev_err(&pdev->dev, "Missing controller reset\n");
> + return PTR_ERR(tdma->rst);
> + }
> + reset_control_reset(tdma->rst);

Is DMA controller clk permanently enabled?

> + /* no support for pd domain hence removing call to add pd
> + * device tegra_pd_add_device(&pdev->dev);
> + */
> +
> + tdma->dma_dev.dev = &pdev->dev;
> +
> + INIT_LIST_HEAD(&tdma->dma_dev.channels);
> + for (i = 0; i < cdata->nr_channels; i++) {
> + struct tegra_dma_channel *tdc = &tdma->channels[i];
> +
> + tdc->chan_base_offset = TEGRA_GPCDMA_CHANNEL_BASE_ADD_OFFSET +
> + start_chan_idx * cdata->channel_reg_size +
> + i * cdata->channel_reg_size;
> + res = platform_get_resource(pdev, IORESOURCE_IRQ,
> + start_chan_idx + i);
> + if (!res) {
> + ret = -EINVAL;
> + dev_err(&pdev->dev, "No irq resource for chan %d\n", i);
> + goto err_irq;
> + }
> + tdc->irq = res->start;
> + snprintf(tdc->name, sizeof(tdc->name), "gpcdma.%d", i);
> +
> + tdc->tdma = tdma;
> + tdc->id = i;
> + tdc->slave_id = -1;
> +
> + vchan_init(&tdc->vc, &tdma->dma_dev);
> + tdc->vc.desc_free = tegra_dma_desc_free;
> + raw_spin_lock_init(&tdc->lock);
> +
> + INIT_LIST_HEAD(&tdc->pending_sg_req);
> + tdc->pending_dma_desc = NULL;
> +
> + /* program stream-id for this channel */
> + tegra_dma_program_sid(tdc, i, stream_id);
> + }
> +
> + dma_cap_set(DMA_SLAVE, tdma->dma_dev.cap_mask);
> + dma_cap_set(DMA_PRIVATE, tdma->dma_dev.cap_mask);
> + dma_cap_set(DMA_MEMCPY, tdma->dma_dev.cap_mask);
> + dma_cap_set(DMA_MEMSET, tdma->dma_dev.cap_mask);
> +
> + /*
> + * Only word aligned transfers are supported. Set the copy
> + * alignment shift.
> + */
> + tdma->dma_dev.copy_align = 2;
> + tdma->dma_dev.fill_align = 2;
> + tdma->dma_dev.device_alloc_chan_resources =
> + tegra_dma_alloc_chan_resources;
> + tdma->dma_dev.device_free_chan_resources =
> + tegra_dma_free_chan_resources;
> + tdma->dma_dev.device_prep_slave_sg = tegra_dma_prep_slave_sg;
> + tdma->dma_dev.device_prep_dma_memcpy = tegra_dma_prep_dma_memcpy;
> + tdma->dma_dev.device_prep_dma_memset = tegra_dma_prep_dma_memset;
> + tdma->dma_dev.device_config = tegra_dma_slave_config;
> + tdma->dma_dev.device_terminate_all = tegra_dma_terminate_all;
> + tdma->dma_dev.device_tx_status = tegra_dma_tx_status;
> + tdma->dma_dev.device_issue_pending = tegra_dma_issue_pending;

What about .device_synchronize()? See tegra20-apb-dma for an example.

> + /* Register DMA channel interrupt handlers after everything is setup */
> + for (i = 0; i < cdata->nr_channels; i++) {
> + struct tegra_dma_channel *tdc = &tdma->channels[i];
> +
> + ret = devm_request_irq(&pdev->dev, tdc->irq,
> + tegra_dma_isr, 0, tdc->name, tdc);
> + if (ret) {
> + dev_err(&pdev->dev,
> + "request_irq failed with err %d channel %d\n",
> + i, ret);
> + goto err_irq;
> + }
> + }
> +
> + ret = dma_async_device_register(&tdma->dma_dev);
> + if (ret < 0) {
> + dev_err(&pdev->dev,
> + "GPC DMA driver registration failed %d\n", ret);
> + goto err_irq;
> + }
> +
> + ret = of_dma_controller_register(pdev->dev.of_node,
> + tegra_dma_of_xlate, tdma);
> + if (ret < 0) {
> + dev_err(&pdev->dev,
> + "GPC DMA OF registration failed %d\n", ret);
> + goto err_unregister_dma_dev;
> + }
> +
> + dev_info(&pdev->dev, "GPC DMA driver register %d channels\n",
> + cdata->nr_channels);
> + return 0;
> +
> +err_unregister_dma_dev:
> + dma_async_device_unregister(&tdma->dma_dev);
> +err_irq:
> + /* no support for pd domain hence removing call to remove pd
> + * device tegra_pd_remove_device(&pdev->dev);
> + */
> + return ret;
> +}
> +
> +static int tegra_dma_remove(struct platform_device *pdev)
> +{
> + struct tegra_dma *tdma = platform_get_drvdata(pdev);
> +

of_dma_controller_free() ?

> + dma_async_device_unregister(&tdma->dma_dev);
> +
> + /* no support for pd domain hence removing call to remove pd
> + * device tegra_pd_remove_device(&pdev->dev);

What is this? Is it borrowed from downstream kernel driver? Upstream
kernel drivers use generic power domain.

> + */
> + return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int tegra_dma_pm_suspend(struct device *dev)

You could mark functions as __maybe_unused and then ifdef isn't needed.

> +{
> + struct tegra_dma *tdma = dev_get_drvdata(dev);
> + int i;
> +
> + for (i = 0; i < tdma->chip_data->nr_channels; i++) {
> + struct tegra_dma_channel *tdc = &tdma->channels[i];
> + struct tegra_dma_channel_regs *ch_reg = &tdc->channel_reg;
> +
> + ch_reg->csr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSR);
> + ch_reg->src_ptr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR);
> + ch_reg->dst_ptr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_DST_PTR);
> + ch_reg->high_addr_ptr = tdc_read(tdc,
> + TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR);
> + ch_reg->mc_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
> + ch_reg->mmio_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ);
> + ch_reg->wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_WCOUNT);
> + }

Why this context save-restore is needed? All channel shall be stopped on
suspend. I think you should remove it, also see tegra20-apb-dma for an
example.

> + return 0;
> +}
> +
> +static int tegra_dma_pm_resume(struct device *dev)
> +{
> + struct tegra_dma *tdma = dev_get_drvdata(dev);
> + int i;
> +
> + for (i = 0; i < tdma->chip_data->nr_channels; i++) {
> + struct tegra_dma_channel *tdc = &tdma->channels[i];
> + struct tegra_dma_channel_regs *ch_reg = &tdc->channel_reg;
> +
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_WCOUNT, ch_reg->wcount);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_DST_PTR, ch_reg->dst_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR, ch_reg->src_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR,
> + ch_reg->high_addr_ptr);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ, ch_reg->mmio_seq);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MCSEQ, ch_reg->mc_seq);
> + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR,
> + (ch_reg->csr & ~TEGRA_GPCDMA_CSR_ENB));
> + }
> + return 0;
> +}
> +
> +#endif
> +
> +static const struct dev_pm_ops tegra_dma_dev_pm_ops = {
> +#ifdef CONFIG_PM_SLEEP
> + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(tegra_dma_pm_suspend, tegra_dma_pm_resume)
> +#endif
> +};
> +
> +static struct platform_driver tegra_dmac_driver = {
> + .driver = {
> + .name = "tegra-gpcdma",
> + .owner = THIS_MODULE,
> + .pm = &tegra_dma_dev_pm_ops,
> + .of_match_table = tegra_dma_of_match,
> + },
> + .probe = tegra_dma_probe,
> + .remove = tegra_dma_remove,
> +};
> +
> +static int __init tegra_dmac_drvinit(void)
> +{
> + return platform_driver_register(&tegra_dmac_driver);
> +}
> +fs_initcall(tegra_dmac_drvinit);

Why fs_initcall? Use module_platform_driver().

> +static void __exit tegra_dmac_drvexit(void)
> +{
> + platform_driver_unregister(&tegra_dmac_driver);
> +}
> +module_exit(tegra_dmac_drvexit);
> +
> +MODULE_ALIAS("platform:tegra-gpc-dma");
> +MODULE_DESCRIPTION("NVIDIA Tegra GPC DMA Controller driver");
> +MODULE_AUTHOR("Pavan Kunapuli <pkunapuli@nvidia.com>");
> +MODULE_AUTHOR("Rajesh Gumasta <rgumasta@nvidia.com>");
> +MODULE_LICENSE("GPL v2");
>