[PATCH v2 2/3] i2c: imx: Check for I2SR_IAL after every byte

[Christian Eggers <ceggers@arri.de>]

Arbitration Lost (IAL) can happen after every single byte transfer. If
arbitration is lost, the I2C hardware will autonomously switch from
master mode to slave. If a transfer is not aborted in this state,
consecutive transfers will not be executed by the hardware and will
timeout.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Cc: stable@vger.kernel.org
---
 drivers/i2c/busses/i2c-imx.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 34648df7f1a6..1db1e2f5296e 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -483,6 +483,24 @@ static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx, bool atomic)
 		dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
 		return -ETIMEDOUT;
 	}
+
+	/* check for arbitration lost */
+	if (i2c_imx->i2csr & I2SR_IAL) {
+		unsigned int temp;
+
+		dev_dbg(&i2c_imx->adapter.dev, "<%s> Arbitration lost\n", __func__);
+		/*
+		 * i2sr_clr_opcode is the value to clear all interrupts.
+		 * Here we want to clear only I2SR_IAL, so we write
+		 * ~i2sr_clr_opcode with just the I2SR_IAL bit toggled.
+		 */
+		temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ I2SR_IAL;
+		imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
+
+		i2c_imx->i2csr = 0;
+		return -EAGAIN;
+	}
+
 	dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
 	i2c_imx->i2csr = 0;
 	return 0;
-- 
Christian Eggers
Embedded software developer

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