linux-kernel - [PATCH] gpio: Return EPROBE_DEFER if gc->to

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Date:   Thu, 14 Oct 2021 16:34:37 +0530
From:   Shreeya Patel <shreeya.patel@...labora.com>
To:     linus.walleij@...aro.org, bgolaszewski@...libre.com, wsa@...nel.org
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org,
        Shreeya Patel <shreeya.patel@...labora.com>
Subject: [PATCH] gpio: Return EPROBE_DEFER if gc->to_irq is NULL

We are racing the registering of .to_irq when probing the
i2c driver. This results in random failure of touchscreen
devices.

Following errors could be seen in dmesg logs when gc->to_irq is NULL

[2.101857] i2c_hid i2c-FTS3528:00: HID over i2c has not been provided an Int IRQ
[2.101953] i2c_hid: probe of i2c-FTS3528:00 failed with error -22

To avoid this situation, defer probing until to_irq is registered.

This issue has been reported many times in past and people have been
using workarounds like changing the pinctrl_amd to built-in instead
of loading it as a module or by adding a softdep for pinctrl_amd into
the config file.

References :-
https://bugzilla.kernel.org/show_bug.cgi?id=209413
https://github.com/Syniurge/i2c-amd-mp2/issues/3

Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
---
 drivers/gpio/gpiolib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 27c07108496d..fc0ba85f4c45 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3084,7 +3084,7 @@ int gpiod_to_irq(const struct gpio_desc *desc)
 
 		return retirq;
 	}
-	return -ENXIO;
+	return -EPROBE_DEFER;
 }
 EXPORT_SYMBOL_GPL(gpiod_to_irq);
 
-- 
2.30.2