linux-kernel - [PATCH 5.7 091/179] i2c: rcar: always clear ICSAR to avoid side effects

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Date:   Mon, 27 Jul 2020 16:04:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Wolfram Sang <wsa@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 091/179] i2c: rcar: always clear ICSAR to avoid side effects

From: Wolfram Sang <wsa+renesas@...g-engineering.com>

[ Upstream commit eb01597158ffb1853a7a7fc2c57d4c844640f75e ]

On R-Car Gen2, we get a timeout when reading from the address set in
ICSAR, even though the slave interface is disabled. Clearing it fixes
this situation. Note that Gen3 is not affected.

To reproduce: bind and undbind an I2C slave on some bus, run
'i2cdetect' on that bus.

Fixes: de20d1857dd6 ("i2c: rcar: add slave support")
Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
Signed-off-by: Wolfram Sang <wsa@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/i2c/busses/i2c-rcar.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 3b5397aa4ca60..50dd98803ca0c 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -868,6 +868,7 @@ static int rcar_unreg_slave(struct i2c_client *slave)
 	/* disable irqs and ensure none is running before clearing ptr */
 	rcar_i2c_write(priv, ICSIER, 0);
 	rcar_i2c_write(priv, ICSCR, 0);
+	rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */
 
 	synchronize_irq(priv->irq);
 	priv->slave = NULL;
@@ -971,6 +972,8 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto out_pm_put;
 
+	rcar_i2c_write(priv, ICSAR, 0); /* Gen2: must be 0 if not using slave */
+
 	if (priv->devtype == I2C_RCAR_GEN3) {
 		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
 		if (!IS_ERR(priv->rstc)) {
-- 
2.25.1