linux-kernel - [PATCH v5 2/3] i2c: imx: Check for I2SR

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Date:   Wed, 7 Oct 2020 10:45:23 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     Oleksij Rempel <linux@...pel-privat.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        "David Laight" <David.Laight@...LAB.COM>
CC:     Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Christian Eggers <ceggers@...i.de>,
        Krzysztof Kozlowski <krzk@...nel.org>, <stable@...r.kernel.org>
Subject: [PATCH v5 2/3] i2c: imx: Check for I2SR_IAL after every byte

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>
Cc: stable@...r.kernel.org
---
 drivers/i2c/busses/i2c-imx.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index cbdcab73a055..63575af41c09 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -490,6 +490,16 @@ 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) {
+		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;
-- 
Christian Eggers
Embedded software developer

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