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Commit 44745bd1 authored by Esben Haabendal's avatar Esben Haabendal Committed by Greg Kroah-Hartman
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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: default avatarEsben Haabendal <eha@deif.com>
Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 86a3d597

drivers/i2c/busses/i2c-imx.c

+4 −4
Original line number Diff line number Diff line
@@ -665,9 +665,6 @@ 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;
@@ -780,6 +777,7 @@ 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",
@@ -806,12 +804,14 @@ 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 */