i2c: imx: Fix race condition in dma read
commit bed4ff1ed4d8f2ef5007c5c6ae1b29c5677a3632 upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 4d297d5..c418830 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -665,9 +665,6 @@
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;
@@ -780,6 +777,7 @@
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",
@@ -806,12 +804,14 @@
*/
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 */