linux-kernel - [PATCH] i2c: rk3x: disable and reenable I2C after timeouts to fix stuck low SDA

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Message-Id: <20210826174632.91887-1-t.schramm@manjaro.org>
Date:   Thu, 26 Aug 2021 19:46:32 +0200
From:   Tobias Schramm <t.schramm@...jaro.org>
To:     linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Tobias Schramm <t.schramm@...jaro.org>
Subject: [PATCH] i2c: rk3x: disable and reenable I2C after timeouts to fix stuck low SDA

Previously the SDA line sometimes remained stuck low after timeouts
rendering the I2C bus unusable. Testing has shown that disabling and
reenabling the I2C peripheral after sending the stop condition seems to
unstick SDA reliably.
Disable and reenable the I2C controller on timeout after sending stop
condition to unstick SDA.

Signed-off-by: Tobias Schramm <t.schramm@...jaro.org>
---
 drivers/i2c/busses/i2c-rk3x.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index 819ab4ee517e..fc330cc3686a 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -1108,6 +1108,16 @@ static int rk3x_i2c_xfer_common(struct i2c_adapter *adap,
 			val |= REG_CON_EN | REG_CON_STOP;
 			i2c_writel(i2c, val, REG_CON);
 
+			/*
+			 * Sometimes SDA remains stuck low after timeouts.
+			 * Disable and reenable the I2C peripheral to unstick
+			 * SDA.
+			 */
+			val &= ~REG_CON_EN;
+			i2c_writel(i2c, val, REG_CON);
+			val |= REG_CON_EN;
+			i2c_writel(i2c, val, REG_CON);
+
 			i2c->state = STATE_IDLE;
 
 			ret = -ETIMEDOUT;
-- 
2.31.1