From: Esben Haabendal <esben.haabendal@gmail.com>
To: linux-i2c@vger.kernel.org
Cc: "Esben Haabendal" <eha@deif.com>,
"Wolfram Sang" <wsa+renesas@sang-engineering.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Lucas Stach" <l.stach@pengutronix.de>,
"Phil Reid" <preid@electromag.com.au>,
"Fabio Estevam" <fabio.estevam@nxp.com>,
"Peter Rosin" <peda@axentia.se>,
linux-kernel@vger.kernel.org
Subject: [PATCH v4 1/3] i2c: imx: Fix race condition in dma read
Date: Thu, 16 Aug 2018 10:43:12 +0200 [thread overview]
Message-ID: <20180816084315.7857-2-esben.haabendal@gmail.com> (raw)
In-Reply-To: <20180816084315.7857-1-esben.haabendal@gmail.com>
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.
Signed-off-by: Esben Haabendal <eha@deif.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
drivers/i2c/busses/i2c-imx.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 498c5e891649..ad6adefb64da 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;
@@ -783,6 +780,7 @@ 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",
@@ -809,12 +807,14 @@ 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 */
--
2.18.0
next parent reply other threads:[~2018-08-16 8:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180816084315.7857-1-esben.haabendal@gmail.com>
2018-08-16 8:43 ` Esben Haabendal [this message]
2018-08-20 9:13 ` [PATCH v4 1/3] i2c: imx: Fix race condition in dma read Wolfram Sang
2018-08-16 8:43 ` [PATCH v4 2/3] i2c: imx: Simplify stopped state tracking Esben Haabendal
2018-08-20 9:14 ` Wolfram Sang
2018-08-20 9:20 ` Esben Haabendal
2018-08-16 8:43 ` [PATCH v4 3/3] arm: dts: ls1021a: Enable I2C DMA support Esben Haabendal
2018-08-16 15:50 ` Uwe Kleine-König
2018-08-20 9:15 ` Wolfram Sang
2018-08-20 9:23 ` Esben Haabendal
2018-08-20 11:14 ` Wolfram Sang
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