On Thu, Aug 09, 2018 at 02:32:05PM +0200, Esben Haabendal wrote: > From: Esben Haabendal <eha@xxxxxxxx> > > 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@xxxxxxxx> > --- > drivers/i2c/busses/i2c-imx.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > index 498c5e891649..f7bd6c21da27 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; > @@ -809,6 +806,8 @@ 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 (i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data) > + temp |= I2CR_DMAEN; Instead of duplicating the if condition I'd do: int use_dma = i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data; and then simplify the two conditions to just "use_dma". With this changed you can add my Ack. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |
