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SubjectRe: [PATCH V3 3/3] i2c: tegra: Add DMA Support
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Date
26.01.2019 6:57, Sowjanya Komatineni пишет:
> This patch adds DMA support for Tegra I2C.
>
> Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
> transfer size of the max FIFO depth and DMA mode is used for
> transfer size higher than max FIFO depth to save CPU overhead.
>
> PIO mode needs full intervention of CPU to fill or empty FIFO's
> and also need to service multiple data requests interrupt for the
> same transaction adding overhead on CPU for large transfers.
>
> DMA mode is helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>
> ---
> [V3] : Updated without additional buffer allocation.
> [V2] : Updated based on V1 review feedback along with code cleanup for
> proper implementation of DMA.
>
> drivers/i2c/busses/i2c-tegra.c | 341 ++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 316 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 3dcbc9960d9d..452358a77400 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -8,6 +8,9 @@
>
> #include <linux/clk.h>
> #include <linux/delay.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dmapool.h>
> +#include <linux/dma-mapping.h>
> #include <linux/err.h>
> #include <linux/i2c.h>
> #include <linux/init.h>
> @@ -45,6 +48,8 @@
> #define I2C_FIFO_CONTROL_RX_FLUSH BIT(0)
> #define I2C_FIFO_CONTROL_TX_TRIG_SHIFT 5
> #define I2C_FIFO_CONTROL_RX_TRIG_SHIFT 2
> +#define I2C_FIFO_CONTROL_TX_TRIG(x) (((x) - 1) << 5)
> +#define I2C_FIFO_CONTROL_RX_TRIG(x) (((x) - 1) << 2)
> #define I2C_FIFO_STATUS 0x060
> #define I2C_FIFO_STATUS_TX_MASK 0xF0
> #define I2C_FIFO_STATUS_TX_SHIFT 4
> @@ -119,6 +124,16 @@
> /* Packet header size in bytes */
> #define I2C_PACKET_HEADER_SIZE 12
>
> +#define DATA_DMA_DIR_TX (1 << 0)
> +#define DATA_DMA_DIR_RX (1 << 1)
> +
> +/*
> + * Upto I2C_PIO_MODE_MAX_LEN bytes, controller will use PIO mode,
> + * above this, controller will use DMA to fill FIFO.
> + * MAX PIO len is 20 bytes excluding packet header.
> + */
> +#define I2C_PIO_MODE_MAX_LEN 20
> +
> /*
> * msg_end_type: The bus control which need to be send at end of transfer.
> * @MSG_END_STOP: Send stop pulse at end of transfer.
> @@ -179,6 +194,7 @@ struct tegra_i2c_hw_feature {
> * @fast_clk: clock reference for fast clock of I2C controller
> * @rst: reset control for the I2C controller
> * @base: ioremapped registers cookie
> + * @phys_addr: Physical address of I2C base address to use for DMA configuration
> * @cont_id: I2C controller ID, used for packet header
> * @irq: IRQ number of transfer complete interrupt
> * @irq_disabled: used to track whether or not the interrupt is enabled
> @@ -192,6 +208,14 @@ struct tegra_i2c_hw_feature {
> * @clk_divisor_non_hs_mode: clock divider for non-high-speed modes
> * @is_multimaster_mode: track if I2C controller is in multi-master mode
> * @xfer_lock: lock to serialize transfer submission and processing
> + * @has_dma: indicated if controller supports DMA

AFAIK, all Terga's support DMA. Let's change to "@has_dma: can utilize DMA" for clarity.

> + * @tx_dma_chan: DMA transmit channel
> + * @rx_dma_chan: DMA receive channel
> + * @dma_phys: handle to DMA resources
> + * @dma_buf: pointer to allocated DMA buffer
> + * @dma_buf_size: DMA buffer size
> + * @is_curr_dma_xfer: indicates active DMA transfer
> + * @dma_complete: DMA completion notifier
> */
> struct tegra_i2c_dev {
> struct device *dev;
> @@ -201,6 +225,7 @@ struct tegra_i2c_dev {
> struct clk *fast_clk;
> struct reset_control *rst;
> void __iomem *base;
> + phys_addr_t phys_addr;
> int cont_id;
> int irq;
> bool irq_disabled;
> @@ -214,8 +239,18 @@ struct tegra_i2c_dev {
> u16 clk_divisor_non_hs_mode;
> bool is_multimaster_mode;
> spinlock_t xfer_lock;
> + bool has_dma;
> + struct dma_chan *tx_dma_chan;
> + struct dma_chan *rx_dma_chan;
> + dma_addr_t dma_phys;
> + u32 *dma_buf;
> + unsigned int dma_buf_size;
> + bool is_curr_dma_xfer;
> + struct completion dma_complete;
> };
>
> +static struct dma_chan *chan;
> +
> static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
> unsigned long reg)
> {
> @@ -282,6 +317,75 @@ static void tegra_i2c_unmask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
> i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
> }
>
> +static void tegra_i2c_dma_complete(void *args)
> +{
> + struct tegra_i2c_dev *i2c_dev = args;
> +
> + complete(&i2c_dev->dma_complete);
> +}
> +
> +static int tegra_i2c_dma_submit(struct tegra_i2c_dev *i2c_dev, size_t len)
> +{
> + struct dma_async_tx_descriptor *dma_desc;
> + enum dma_transfer_direction dir;
> +
> + dev_dbg(i2c_dev->dev, "Starting DMA for length: %zu\n", len);
> + reinit_completion(&i2c_dev->dma_complete);
> + dir = i2c_dev->msg_read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> + dma_desc = dmaengine_prep_slave_single(chan, i2c_dev->dma_phys,
> + len, dir, DMA_PREP_INTERRUPT |
> + DMA_CTRL_ACK);
> + if (!dma_desc) {
> + dev_err(i2c_dev->dev, "Failed to get DMA descriptor\n");
> + return -EIO;
> + }
> +
> + dma_desc->callback = tegra_i2c_dma_complete;
> + dma_desc->callback_param = i2c_dev;
> + dmaengine_submit(dma_desc);
> + dma_async_issue_pending(chan);
> + return 0;
> +}
> +
> +static int tegra_i2c_init_dma_param(struct tegra_i2c_dev *i2c_dev,
> + bool dma_to_memory)
> +{
> + struct dma_chan *dma_chan;
> + u32 *dma_buf;
> + dma_addr_t dma_phys;
> + int ret;
> + const char *chan_name = dma_to_memory ? "rx" : "tx";
> +
> + dma_chan = dma_request_slave_channel_reason(i2c_dev->dev, chan_name);
> + if (IS_ERR(dma_chan))
> + return PTR_ERR(dma_chan);
> +
> + dma_buf = dma_alloc_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> + &dma_phys, GFP_KERNEL);
> +
> + if (!dma_buf) {
> + dev_err(i2c_dev->dev, "Failed to allocate the DMA buffer\n");
> + ret = -ENOMEM;
> + goto scrub;
> + }
> +
> + if (dma_to_memory)
> + i2c_dev->rx_dma_chan = dma_chan;
> + else
> + i2c_dev->tx_dma_chan = dma_chan;
> +
> + i2c_dev->dma_buf = dma_buf;
> + i2c_dev->dma_phys = dma_phys;
> +
> + return 0;
> +
> +scrub:
> + dma_free_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> + dma_buf, dma_phys);

Will dma_free_coherent() handle NULL ptr which will happen when dma_buf allocation fails for the RX init'ing?

> + dma_release_channel(dma_chan);
> + return ret;
> +}
> +
> static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
> {
> unsigned long timeout = jiffies + HZ;
> @@ -641,25 +745,45 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> goto err;
> }
>
> - if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> - if (i2c_dev->msg_buf_remaining)
> - tegra_i2c_empty_rx_fifo(i2c_dev);
> - else
> - BUG();
> - }
> + if (!i2c_dev->is_curr_dma_xfer) {
> + if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> + if (i2c_dev->msg_buf_remaining)
> + tegra_i2c_empty_rx_fifo(i2c_dev);
> + else
> + BUG();
> + }
>
> - if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> - if (i2c_dev->msg_buf_remaining)
> - tegra_i2c_fill_tx_fifo(i2c_dev);
> - else
> - tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
> + if (!i2c_dev->msg_read &&
> + (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> + if (i2c_dev->msg_buf_remaining)
> + tegra_i2c_fill_tx_fifo(i2c_dev);
> + else
> + tegra_i2c_mask_irq(i2c_dev,
> + I2C_INT_TX_FIFO_DATA_REQ);
> + }
> }
>
> i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> if (i2c_dev->is_dvc)
> dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>
> - if (status & I2C_INT_PACKET_XFER_COMPLETE) {
> + if (status & I2C_INT_ALL_PACKETS_XFER_COMPLETE) {
> + /*
> + * During message read XFER_COMPLETE interrupt is triggered prior to
> + * DMA complete notification and during message write XFER_COMPLETE
> + * interrupt is triggered after DMA complete notification.
> + * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer.
> + * so forcing msg_buf_remaining to 0.
> + */
> + if (i2c_dev->is_curr_dma_xfer)
> + i2c_dev->msg_buf_remaining = 0;
> + status |= I2C_INT_PACKET_XFER_COMPLETE;
> + i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> + if (!i2c_dev->msg_buf_remaining)
> + complete(&i2c_dev->msg_complete);
> + } else if (status & I2C_INT_PACKET_XFER_COMPLETE) {
> + if (i2c_dev->is_curr_dma_xfer)
> + i2c_dev->msg_buf_remaining = 0;
> BUG_ON(i2c_dev->msg_buf_remaining);
> complete(&i2c_dev->msg_complete);
> }
> @@ -668,17 +792,68 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
> /* An error occurred, mask all interrupts */
> tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
> I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
> - I2C_INT_RX_FIFO_DATA_REQ);
> + I2C_INT_RX_FIFO_DATA_REQ | I2C_INT_ALL_PACKETS_XFER_COMPLETE);
> i2c_writel(i2c_dev, status, I2C_INT_STATUS);
> if (i2c_dev->is_dvc)
> dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>
> + if (i2c_dev->is_curr_dma_xfer) {
> + dmaengine_terminate_all(chan);
> + complete(&i2c_dev->dma_complete);
> + }
> +
> complete(&i2c_dev->msg_complete);
> done:
> spin_unlock(&i2c_dev->xfer_lock);
> return IRQ_HANDLED;
> }
>
> +static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
> + size_t len, int direction)
> +{
> + u32 val, reg;
> + u8 dma_burst = 0;
> + struct dma_slave_config dma_sconfig;
> +
> + if (i2c_dev->hw->has_mst_fifo)
> + reg = I2C_MST_FIFO_CONTROL;
> + else
> + reg = I2C_FIFO_CONTROL;
> + val = i2c_readl(i2c_dev, reg);
> +
> + if (len & 0xF)
> + dma_burst = 1;
> + else if (len & 0x10)
> + dma_burst = 4;
> + else
> + dma_burst = 8;

I'm still wondering whether dma_burst < 8 negatively affects transfer efficiency. Could you please clarify?

> +
> + if (direction == DATA_DMA_DIR_TX) {
> + if (i2c_dev->hw->has_mst_fifo)
> + val |= I2C_MST_FIFO_CONTROL_TX_TRIG(dma_burst);
> + else
> + val |= I2C_FIFO_CONTROL_TX_TRIG(dma_burst);
> + } else {
> + if (i2c_dev->hw->has_mst_fifo)
> + val |= I2C_MST_FIFO_CONTROL_RX_TRIG(dma_burst);
> + else
> + val |= I2C_FIFO_CONTROL_RX_TRIG(dma_burst);
> + }
> + i2c_writel(i2c_dev, val, reg);
> +
> + if (direction == DATA_DMA_DIR_TX) {
> + dma_sconfig.dst_addr = i2c_dev->phys_addr + I2C_TX_FIFO;
> + dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.dst_maxburst = dma_burst;
> + } else {
> + dma_sconfig.src_addr = i2c_dev->phys_addr + I2C_RX_FIFO;
> + dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.src_maxburst = dma_burst;
> + }
> +
> + dmaengine_slave_config(chan, &dma_sconfig);
> +}
> +
> static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> struct i2c_msg *msg, enum msg_end_type end_state)
> {
> @@ -688,6 +863,9 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> unsigned long flags;
> u16 xfer_time = 100;
> size_t xfer_size = 0;
> + u32 *buffer = 0;
> + int ret = 0;
> + bool dma = false;
>
> if (msg->flags & I2C_M_RD)
> xfer_size = ALIGN(msg->len, BYTES_PER_FIFO_WORD);
> @@ -698,6 +876,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> xfer_time += DIV_ROUND_CLOSEST((xfer_size * 9) * 1000,
> i2c_dev->bus_clk_rate);
>
> + dma = ((xfer_size > I2C_PIO_MODE_MAX_LEN) &&
> + i2c_dev->tx_dma_chan && i2c_dev->rx_dma_chan);

There is no need to allocate resources for DMA until dma==true, let's postpone channels requesting and dma_buf allocation until they are really needed.

Please factor out DMA resorces allocation into something like this:

int tegra_i2c_init_dma_resorces(struct tegra_i2c_dev *i2c_dev)
{
struct dma_chan *dma_rx, *dma_tx;
dma_addr_t dma_phys;
u32 *dma_buf;
int err;

if (i2c_dev->dma_buf)
return 0;

if (!i2c_dev->has_dma)
return -EINVAL;

dma_rx = dma_request_slave_channel_reason(i2c_dev->dev, "rx");
if (IS_ERR(dma_rx))
return PTR_ERR(dma_rx);

dma_tx = dma_request_slave_channel_reason(i2c_dev->dev, "tx");
if (IS_ERR(dma_tx)) {
err = PTR_ERR(dma_tx);
goto err_release_rx;
}

dma_buf = dma_alloc_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
&dma_phys, GFP_KERNEL | __GFP_NOWARN);
if (!dma_buf) {
dev_err(i2c_dev->dev, "Failed to allocate the DMA buffer\n");
err = -ENOMEM;
goto err_release_tx;
}

i2c_dev->dma_buf = dma_buf;
i2c_dev->dma_phys = dma_phys;
i2c_dev->rx_dma_chan = dma_rx;
i2c_dev->tx_dma_chan = dma_tx;

err_release_tx:
dma_release_channel(dma_tx);
err_release_rx:
dma_release_channel(dma_rx);

return err;
}

...

and then:

dma = (xfer_size > I2C_PIO_MODE_MAX_LEN);
if (dma) {
err = tegra_i2c_init_dma_resorces(i2c_dev);
if (err)
dma = false;
}

> +
> + i2c_dev->is_curr_dma_xfer = dma;
> +
> tegra_i2c_flush_fifos(i2c_dev);
>
> i2c_dev->msg_buf = msg->buf;
> @@ -711,14 +894,50 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
> tegra_i2c_unmask_irq(i2c_dev, int_mask);
>
> + if (dma) {
> + if (i2c_dev->msg_read) {
> + chan = i2c_dev->rx_dma_chan;
> + tegra_i2c_config_fifo_trig(i2c_dev, xfer_size,
> + DATA_DMA_DIR_RX);
> + /* make the dma buffer to read by dma */
> + dma_sync_single_for_device(i2c_dev->dev,
> + i2c_dev->dma_phys,
> + i2c_dev->dma_buf_size,

Why not use the size of transfer for the syncing?

> + DMA_FROM_DEVICE);
> + ret = tegra_i2c_dma_submit(i2c_dev, xfer_size);
> + if (ret < 0) {
> + dev_err(i2c_dev->dev,
> + "Starting RX DMA failed, err %d\n",
> + ret);
> + goto exit;
> + }
> + } else {
> + chan = i2c_dev->tx_dma_chan;
> + tegra_i2c_config_fifo_trig(i2c_dev, xfer_size,
> + DATA_DMA_DIR_TX);
> + /* Make the dma buffer to read by cpu */
> + dma_sync_single_for_cpu(i2c_dev->dev,
> + i2c_dev->dma_phys,
> + i2c_dev->dma_buf_size,> + DMA_TO_DEVICE);
> + buffer = (u32 *)i2c_dev->dma_buf;
> + }
> + }
> +
> packet_header = (0 << PACKET_HEADER0_HEADER_SIZE_SHIFT) |
> PACKET_HEADER0_PROTOCOL_I2C |
> (i2c_dev->cont_id << PACKET_HEADER0_CONT_ID_SHIFT) |
> (1 << PACKET_HEADER0_PACKET_ID_SHIFT);
> - i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> + if (dma && !i2c_dev->msg_read)
> + *buffer++ = packet_header;
> + else
> + i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
>
> packet_header = msg->len - 1;
> - i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> + if (dma && !i2c_dev->msg_read)
> + *buffer++ = packet_header;
> + else
> + i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
>
> packet_header = I2C_HEADER_IE_ENABLE;
> if (end_state == MSG_END_CONTINUE)
> @@ -735,29 +954,85 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
> packet_header |= I2C_HEADER_CONT_ON_NAK;
> if (msg->flags & I2C_M_RD)
> packet_header |= I2C_HEADER_READ;
> - i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> -
> - if (!(msg->flags & I2C_M_RD))
> - tegra_i2c_fill_tx_fifo(i2c_dev);
> -
> + if (dma && !i2c_dev->msg_read)
> + *buffer++ = packet_header;
> + else
> + i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> +
> + if (!i2c_dev->msg_read) {
> + if (dma) {
> + memcpy(buffer, msg->buf, msg->len);
> + /* make the dma buffer to read by dma */
> + dma_sync_single_for_device(i2c_dev->dev,
> + i2c_dev->dma_phys,
> + i2c_dev->dma_buf_size,
> + DMA_TO_DEVICE);
> + ret = tegra_i2c_dma_submit(i2c_dev, xfer_size);
> + if (ret < 0) {
> + dev_err(i2c_dev->dev,
> + "Starting TX DMA failed, err %d\n",
> + ret);
> + goto exit;
> + }
> + } else {
> + tegra_i2c_fill_tx_fifo(i2c_dev);
> + }
> + }
> if (i2c_dev->hw->has_per_pkt_xfer_complete_irq)
> int_mask |= I2C_INT_PACKET_XFER_COMPLETE;
> - if (msg->flags & I2C_M_RD)
> - int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
> - else if (i2c_dev->msg_buf_remaining)
> - int_mask |= I2C_INT_TX_FIFO_DATA_REQ;
> + if (dma) {
> + int_mask |= I2C_INT_ALL_PACKETS_XFER_COMPLETE;
> + } else {
> + if (msg->flags & I2C_M_RD)
> + int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
> + else if (i2c_dev->msg_buf_remaining)
> + int_mask |= I2C_INT_TX_FIFO_DATA_REQ;
> + }
>
> tegra_i2c_unmask_irq(i2c_dev, int_mask);
> - spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags);
> dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n",
> i2c_readl(i2c_dev, I2C_INT_MASK));
>
> +exit:
> + spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags);
> + if (ret)
> + return ret;
> +
> + if (dma) {
> + time_left = wait_for_completion_timeout(
> + &i2c_dev->dma_complete,
> + TEGRA_I2C_TIMEOUT(xfer_time));
> +
> + if (time_left == 0) {
> + dev_err(i2c_dev->dev, "DMA transfer timeout\n");
> + dmaengine_terminate_all(chan);
> + tegra_i2c_init(i2c_dev);
> + return -ETIMEDOUT;
> + }
> +
> + if (i2c_dev->msg_read) {
> + if (likely(i2c_dev->msg_err == I2C_ERR_NONE)) {
> + dma_sync_single_for_cpu(i2c_dev->dev,
> + i2c_dev->dma_phys,
> + i2c_dev->dma_buf_size,
> + DMA_FROM_DEVICE);
> +
> + memcpy(i2c_dev->msg_buf, i2c_dev->dma_buf,
> + msg->len);
> + }
> + }
> + }
> +
> time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> TEGRA_I2C_TIMEOUT(xfer_time));
> tegra_i2c_mask_irq(i2c_dev, int_mask);
>
> if (time_left == 0) {
> dev_err(i2c_dev->dev, "i2c transfer timed out\n");
> + if (dma) {
> + dmaengine_terminate_all(chan);
> + complete(&i2c_dev->dma_complete);
> + }
>
> tegra_i2c_init(i2c_dev);
> return -ETIMEDOUT;
> @@ -835,6 +1110,8 @@ static void tegra_i2c_parse_dt(struct tegra_i2c_dev *i2c_dev)
>
> i2c_dev->is_multimaster_mode = of_property_read_bool(np,
> "multi-master");
> +
> + i2c_dev->has_dma = of_property_read_bool(np, "dmas");
> }
>
> static const struct i2c_algorithm tegra_i2c_algo = {
> @@ -947,11 +1224,13 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> struct clk *div_clk;
> struct clk *fast_clk;
> void __iomem *base;
> + phys_addr_t phys_addr;
> int irq;
> int ret = 0;
> int clk_multiplier = I2C_CLK_MULTIPLIER_STD_FAST_MODE;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + phys_addr = res->start;
> base = devm_ioremap_resource(&pdev->dev, res);
> if (IS_ERR(base))
> return PTR_ERR(base);
> @@ -974,12 +1253,14 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> return -ENOMEM;
>
> i2c_dev->base = base;
> + i2c_dev->phys_addr = phys_addr;
> i2c_dev->div_clk = div_clk;
> i2c_dev->adapter.algo = &tegra_i2c_algo;
> i2c_dev->adapter.quirks = &tegra_i2c_quirks;
> i2c_dev->irq = irq;
> i2c_dev->cont_id = pdev->id;
> i2c_dev->dev = &pdev->dev;
> + i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_write_len;
>
> i2c_dev->rst = devm_reset_control_get_exclusive(&pdev->dev, "i2c");
> if (IS_ERR(i2c_dev->rst)) {
> @@ -994,6 +1275,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> "nvidia,tegra20-i2c-dvc");
> init_completion(&i2c_dev->msg_complete);
> spin_lock_init(&i2c_dev->xfer_lock);
> + init_completion(&i2c_dev->dma_complete);
>
> if (!i2c_dev->hw->has_single_clk_source) {
> fast_clk = devm_clk_get(&pdev->dev, "fast-clk");
> @@ -1053,6 +1335,15 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> }
> }
>
> + if (i2c_dev->has_dma) {
> + ret = tegra_i2c_init_dma_param(i2c_dev, true);
> + if (ret == -EPROBE_DEFER)
> + goto disable_div_clk;

So now dma_buf has been allocated by initing the RX channel.

> + ret = tegra_i2c_init_dma_param(i2c_dev, false);

And now dma_buf will be allocated second time for the TX?

> + if (ret == -EPROBE_DEFER)
> + goto disable_div_clk;

Where is RX channel releasing when TX init fails?

> + }
No channels / dma_buf releasing in tegra_i2c_remove()?

> +
> ret = tegra_i2c_init(i2c_dev);
> if (ret) {
> dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
>

Please collect performance stats before posting new version of the patch.

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