linux-kernel - [PATCH] i2c: rcar: ensure Gen3+ reset does not disturb local targets

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Message-ID: <20240711083043.8334-2-wsa+renesas@sang-engineering.com>
Date: Thu, 11 Jul 2024 10:30:44 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: linux-renesas-soc@...r.kernel.org
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] i2c: rcar: ensure Gen3+ reset does not disturb local targets

R-Car Gen3+ needs a reset before every controller transfer. That erases
configuration of a potentially in parallel running local target
instance. To avoid this disruption, avoid controller transfers if a
local target is running. Also, disable SMBusHostNotify because it
requires being a controller and local target at the same time.

Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 8f2ede534f30..29cbeda59f3e 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -884,6 +884,10 @@ static int rcar_i2c_do_reset(struct rcar_i2c_priv *priv)
 {
 	int ret;
 
+	/* Don't reset if a slave instance is currently running */
+	if (priv->slave)
+		return -EISCONN;
+
 	ret = reset_control_reset(priv->rstc);
 	if (ret)
 		return ret;
@@ -1176,6 +1180,7 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	if (of_property_read_bool(dev->of_node, "smbus"))
 		priv->flags |= ID_P_HOST_NOTIFY;
 
+	/* R-Car Gen3+ needs a reset before every transfer */
 	if (priv->devtype >= I2C_RCAR_GEN3) {
 		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
 		if (IS_ERR(priv->rstc)) {
@@ -1186,6 +1191,9 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 		ret = reset_control_status(priv->rstc);
 		if (ret < 0)
 			goto out_pm_put;
+
+		/* hard reset disturbs HostNotify local target, so disable it */
+		priv->flags &= ~ID_P_HOST_NOTIFY;
 	}
 
 	ret = platform_get_irq(pdev, 0);
-- 
2.43.0