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i2c: imx: Fix race condition in dma read 

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 <eha@deif.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
This commit is contained in:
Esben Haabendal 2018-08-16 10:43:12 +02:00 committed by Wolfram Sang
parent 5c18d12ced
commit bed4ff1ed4
1 changed files with 4 additions and 4 deletions
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8
drivers/i2c/busses/i2c-imx.c
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@ -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 imx_i2c_dma *dma = i2c_imx->dma;
struct device *dev = &i2c_imx->adapter.dev; 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->chan_using = dma->chan_rx;
dma->dma_transfer_dir = DMA_DEV_TO_MEM; dma->dma_transfer_dir = DMA_DEV_TO_MEM;
@ -784,6 +781,7 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, bo
int i, result; int i, result;
unsigned int temp; unsigned int temp;
int block_data = msgs->flags & I2C_M_RECV_LEN; 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, dev_dbg(&i2c_imx->adapter.dev,
"<%s> write slave address: addr=0x%x\n", "<%s> write slave address: addr=0x%x\n",
@ -810,12 +808,14 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs, bo
*/ */
if ((msgs->len - 1) || block_data) if ((msgs->len - 1) || block_data)
temp &= ~I2CR_TXAK; temp &= ~I2CR_TXAK;
if (use_dma)
temp |= I2CR_DMAEN;
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */ imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__); 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); return i2c_imx_dma_read(i2c_imx, msgs, is_lastmsg);
/* read data */ /* read data */