[PATCH v3] gpio: Return EPROBE_DEFER if gc->to_irq is NULL

From: Shreeya Patel
Date: Mon Nov 15 2021 - 17:21:55 EST


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.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=209413

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Shreeya Patel <shreeya.patel@xxxxxxxxxxxxx>

---
Changes in v3
- Fix the error reported by kernel test robot.

Changes in v2
- Add a condition to check for irq chip to avoid bogus error.
---
drivers/gpio/gpiolib.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index abfbf546d159..4d7fb349e837 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3111,6 +3111,16 @@ int gpiod_to_irq(const struct gpio_desc *desc)

return retirq;
}
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+ if (gc->irq.chip) {
+ /*
+ * avoid race condition with other code, which tries to lookup
+ * an IRQ before the irqchip has been properly registered,
+ * i.e. while gpiochip is still being brought up.
+ */
+ return -EPROBE_DEFER;
+ }
+#endif
return -ENXIO;
}
EXPORT_SYMBOL_GPL(gpiod_to_irq);
--
2.30.2