From: Esben Haabendal <[email protected]>
This fixes a race condition, where the DMAEN bit ends up being set after
I2C slave has transmitted a byte following the dummy read. When that
happens, an interrupt is generated instead, and no DMA request is generated
to kickstart the DMA read, and a timeout happens after DMA_TIMEOUT (1 sec).
Fixed by setting the DMAEN bit before the dummy read.
Signed-off-by: Esben Haabendal <[email protected]>
Acked-by: Uwe Kleine-König <[email protected]>
---
drivers/i2c/busses/i2c-imx.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 498c5e891649..ad6adefb64da 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -668,9 +668,6 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
struct imx_i2c_dma *dma = i2c_imx->dma;
struct device *dev = &i2c_imx->adapter.dev;
- temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
- temp |= I2CR_DMAEN;
- imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
dma->chan_using = dma->chan_rx;
dma->dma_transfer_dir = DMA_DEV_TO_MEM;
@@ -783,6 +780,7 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, bo
int i, result;
unsigned int temp;
int block_data = msgs->flags & I2C_M_RECV_LEN;
+ int use_dma = i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data;
dev_dbg(&i2c_imx->adapter.dev,
"<%s> write slave address: addr=0x%x\n",
@@ -809,12 +807,14 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, bo
*/
if ((msgs->len - 1) || block_data)
temp &= ~I2CR_TXAK;
+ if (use_dma)
+ temp |= I2CR_DMAEN;
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);
- if (i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data)
+ if (use_dma)
return i2c_imx_dma_read(i2c_imx, msgs, is_lastmsg);
/* read data */
--
2.18.0
On Thu, Aug 16, 2018 at 10:43:12AM +0200, Esben Haabendal wrote:
> From: Esben Haabendal <[email protected]>
>
> This fixes a race condition, where the DMAEN bit ends up being set after
> I2C slave has transmitted a byte following the dummy read. When that
> happens, an interrupt is generated instead, and no DMA request is generated
> to kickstart the DMA read, and a timeout happens after DMA_TIMEOUT (1 sec).
>
> Fixed by setting the DMAEN bit before the dummy read.
>
> Signed-off-by: Esben Haabendal <[email protected]>
> Acked-by: Uwe Kleine-König <[email protected]>
Applied to for-next and added stable, thanks!