[PATCH v6 3/3] i2c: imx: Don't generate STOP condition if arbitration has been lost

Christian Eggers
2020-10-09T11:07:33Z

If arbitration is lost, the master automatically changes to slave mode.
I2SR_IBB may or may not be reset by hardware. Raising a STOP condition
by resetting I2CR_MSTA has no effect and will not clear I2SR_IBB.

So calling i2c_imx_bus_busy() is not required and would busy-wait until
timeout.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Tested (not extensively) on Vybrid VF500 (Toradex VF50):
Tested-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: stable@vger.kernel.org # Requires trivial backporting, simple remove
# the 3rd argument from the calls to
# i2c_imx_bus_busy().
---
drivers/i2c/busses/i2c-imx.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 69ce5eea9b5a..e98356f3db84 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -615,6 +615,8 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx, bool atomic)
/* Stop I2C transaction */
dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+ if (!(temp & I2CR_MSTA))
+ i2c_imx->stopped = 1;
temp &= ~(I2CR_MSTA | I2CR_MTX);
if (i2c_imx->dma)
temp &= ~I2CR_DMAEN;
@@ -778,9 +780,12 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
*/
dev_dbg(dev, "<%s> clear MSTA\n", __func__);
temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+ if (!(temp & I2CR_MSTA))
+ i2c_imx->stopped = 1;
temp &= ~(I2CR_MSTA | I2CR_MTX);
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
- i2c_imx_bus_busy(i2c_imx, 0, false);
+ if (!i2c_imx->stopped)
+ i2c_imx_bus_busy(i2c_imx, 0, false);
} else {
/*
* For i2c master receiver repeat restart operation like:
@@ -905,9 +910,12 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
dev_dbg(&i2c_imx->adapter.dev,
"<%s> clear MSTA\n", __func__);
temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+ if (!(temp & I2CR_MSTA))
+ i2c_imx->stopped = 1;
temp &= ~(I2CR_MSTA | I2CR_MTX);
imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
- i2c_imx_bus_busy(i2c_imx, 0, atomic);
+ if (!i2c_imx->stopped)
+ i2c_imx_bus_busy(i2c_imx, 0, atomic);
} else {
/*
* For i2c master receiver repeat restart operation like:
--
Christian Eggers
Embedded software developer

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