linux-kernel - [RFC PATCH] i2c: at91: Fix pinmux after devm_gpiod

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Message-ID: <20200415070643.23663-1-codrin.ciubotariu@microchip.com>
Date:   Wed, 15 Apr 2020 10:06:43 +0300
From:   Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
To:     <linux-gpio@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <ludovic.desroches@...rochip.com>, <nicolas.ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <kamel.bouhara@...tlin.com>,
        <linux@...linux.org.uk>, <linus.walleij@...aro.org>,
        <alan@...tiron.com>, <wsa@...-dreams.de>,
        Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Subject: [RFC PATCH] i2c: at91: Fix pinmux after devm_gpiod_get() for bus recovery

devm_gpiod_get() usually calls gpio_request_enable() for non-strict pinmux
drivers. These puts the pins in GPIO mode, whithout notifying the pinctrl
driver. At this point, the I2C bus no longer owns the pins. To mux the
pins back to the I2C bus, we use the pinctrl driver to change the state
of the pins to GPIO, before using devm_gpiod_get(). After the pins are
received as GPIOs, we switch theer pinctrl state back to the default
one,

Fixes: d3d3fdcc4c90 ("i2c: at91: implement i2c bus recovery")
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
---
 drivers/i2c/busses/i2c-at91-master.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
index 0aba51a7df32..43d85845c897 100644
--- a/drivers/i2c/busses/i2c-at91-master.c
+++ b/drivers/i2c/busses/i2c-at91-master.c
@@ -845,6 +845,18 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
 							 PINCTRL_STATE_DEFAULT);
 	dev->pinctrl_pins_gpio = pinctrl_lookup_state(dev->pinctrl,
 						      "gpio");
+	if (IS_ERR(dev->pinctrl_pins_default) ||
+	    IS_ERR(dev->pinctrl_pins_gpio)) {
+		dev_info(&pdev->dev, "pinctrl states incomplete for recovery\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * pins will be taken as GPIO, so we might as well inform pinctrl about
+	 * this and move the state to GPIO
+	 */
+	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_gpio);
+
 	rinfo->sda_gpiod = devm_gpiod_get(&pdev->dev, "sda", GPIOD_IN);
 	if (PTR_ERR(rinfo->sda_gpiod) == -EPROBE_DEFER)
 		return -EPROBE_DEFER;
@@ -855,9 +867,7 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
 		return -EPROBE_DEFER;
 
 	if (IS_ERR(rinfo->sda_gpiod) ||
-	    IS_ERR(rinfo->scl_gpiod) ||
-	    IS_ERR(dev->pinctrl_pins_default) ||
-	    IS_ERR(dev->pinctrl_pins_gpio)) {
+	    IS_ERR(rinfo->scl_gpiod)) {
 		dev_info(&pdev->dev, "recovery information incomplete\n");
 		if (!IS_ERR(rinfo->sda_gpiod)) {
 			gpiod_put(rinfo->sda_gpiod);
@@ -870,6 +880,9 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev,
 		return -EINVAL;
 	}
 
+	/* change the state of the pins back to their default state */
+	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);
+
 	dev_info(&pdev->dev, "using scl, sda for recovery\n");
 
 	rinfo->prepare_recovery = at91_prepare_twi_recovery;
-- 
2.20.1