linux-kernel - [PATCH 5.4 38/54] i2c: imx: Check for I2SR

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Message-Id: <20201210142603.908115809@linuxfoundation.org>
Date:   Thu, 10 Dec 2020 15:27:15 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christian Eggers <ceggers@...i.de>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Wolfram Sang <wsa@...nel.org>
Subject: [PATCH 5.4 38/54] i2c: imx: Check for I2SR_IAL after every byte

From: Christian Eggers <ceggers@...i.de>

commit 1de67a3dee7a279ebe4d892b359fe3696938ec15 upstream.

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@...i.de>
Tested (not extensively) on Vybrid VF500 (Toradex VF50):
Tested-by: Krzysztof Kozlowski <krzk@...nel.org>
Acked-by: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: stable@...r.kernel.org
Signed-off-by: Wolfram Sang <wsa@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/i2c/busses/i2c-imx.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -470,6 +470,16 @@ static int i2c_imx_trx_complete(struct i
 		dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
 		return -ETIMEDOUT;
 	}
+
+	/* check for arbitration lost */
+	if (i2c_imx->i2csr & I2SR_IAL) {
+		dev_dbg(&i2c_imx->adapter.dev, "<%s> Arbitration lost\n", __func__);
+		i2c_imx_clear_irq(i2c_imx, I2SR_IAL);
+
+		i2c_imx->i2csr = 0;
+		return -EAGAIN;
+	}
+
 	dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
 	i2c_imx->i2csr = 0;
 	return 0;