[PATCH] i2c: rcar: always clear ICSAR to avoid side effects

From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: linux-i2c@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>
Subject: [PATCH] i2c: rcar: always clear ICSAR to avoid side effects
Date: Sat,  4 Jul 2020 15:38:29 +0200	[thread overview]
Message-ID: <20200704133829.7015-1-wsa+renesas@sang-engineering.com> (raw)

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.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 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 5b70047c6589..2c7c4afc15d4 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -874,6 +874,7 @@ 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;
@@ -982,6 +983,8 @@ 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)) {
-- 
2.20.1

