From eb01597158ffb1853a7a7fc2c57d4c844640f75e Mon Sep 17 00:00:00 2001
From: Wolfram Sang <wsa+renesas@sang-engineering.com>
Date: Sat, 4 Jul 2020 15:38:29 +0200
Subject: [PATCH] i2c: rcar: always clear ICSAR to avoid side effects
Git-commit: eb01597158ffb1853a7a7fc2c57d4c844640f75e
Patch-mainline: v5.8-rc7
References: git-fixes

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@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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 a45c4bf1ec01..2e3e1bb75013 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;
@@ -969,6 +970,8 @@ 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)) {
-- 
2.16.4