Message ID | 20180523095623.3347-3-esben.haabendal@gmail.com |
---|---|
State | Superseded |
Headers | show |
Series | i2c: imx: Fix and enable DMA support for LS1021A | expand |
On Wed, May 23, 2018 at 11:56:21AM +0200, Esben Haabendal wrote: > From: Esben Haabendal <eha@deif.com> > > 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. Does this fix the problem or just narrow the race window? Best regards Uwe
Uwe Kleine-König <u.kleine-koenig@pengutronix.de> writes: > On Wed, May 23, 2018 at 11:56:21AM +0200, Esben Haabendal wrote: >> From: Esben Haabendal <eha@deif.com> >> >> 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. > > Does this fix the problem or just narrow the race window? It should fix the problem. /Esben
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 6fca5e64cffb..742b548437af 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -677,9 +677,6 @@ 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; @@ -819,6 +816,11 @@ 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; imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); + if (i2c_imx->dma && msgs->len >= DMA_THRESHOLD && !block_data) { + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); + 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__);