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authorEsben Haabendal <eha@deif.com>2018-08-16 10:43:12 +0200
committerWolfram Sang <wsa@the-dreams.de>2018-08-20 11:13:09 +0200
commitbed4ff1ed4d8f2ef5007c5c6ae1b29c5677a3632 (patch)
tree62e0e8b251ca36d6eadee3df8013e36962b23a37 /drivers/i2c/busses
parent5c18d12ced225fa0ad5a03fb42bbb293815d1342 (diff)
downloadlinux-stericsson-bed4ff1ed4d8f2ef5007c5c6ae1b29c5677a3632.tar.gz
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-K├Ânig <u.kleine-koenig@pengutronix.de> Signed-off-by: Wolfram Sang <wsa@the-dreams.de> Cc: stable@kernel.org
Diffstat (limited to 'drivers/i2c/busses')
-rw-r--r--drivers/i2c/busses/i2c-imx.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 0207e194f84b..eb11ac3d6aba 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;
@@ -784,6 +781,7 @@ 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",
@@ -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)
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 */