linux-kernel - [PATCH] gpio: aggregator: Fix calling into sleeping GPIO controllers

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Message-Id: <6a62a531227cd4f20d77d50cdde60c7a18b9f052.1643625325.git.geert+renesas@glider.be>
Date:   Mon, 31 Jan 2022 11:35:53 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Mikko Salomäki <ms@...arespons.se>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] gpio: aggregator: Fix calling into sleeping GPIO controllers

If the parent GPIO controller is a sleeping controller (e.g. a GPIO
controller connected to I2C), getting or setting a GPIO triggers a
might_sleep() warning.  This happens because the GPIO Aggregator takes
the can_sleep flag into account only for its internal locking, not for
calling into the parent GPIO controller.

Fix this by using the gpiod_[gs]et*_cansleep() APIs when calling into a
sleeping GPIO controller.

Reported-by: Mikko Salomäki <ms@...arespons.se>
Fixes: 828546e24280f721 ("gpio: Add GPIO Aggregator")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
I considered splitting the .[gs]et{_multiple}() callbacks for the
sleeping vs. nonsleeping cases, but the code size increase (measured on
ARM) would be substantial:
  +64 bytes for gpio_fwd_[gs]et_cansleep(),
  +296 bytes for gpio_fwd_[gs]et_multiple_cansleep().
---
 drivers/gpio/gpio-aggregator.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
index 869dc952cf45218b..0cb2664085cf8314 100644
--- a/drivers/gpio/gpio-aggregator.c
+++ b/drivers/gpio/gpio-aggregator.c
@@ -278,7 +278,8 @@ static int gpio_fwd_get(struct gpio_chip *chip, unsigned int offset)
 {
 	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
 
-	return gpiod_get_value(fwd->descs[offset]);
+	return chip->can_sleep ? gpiod_get_value_cansleep(fwd->descs[offset])
+			       : gpiod_get_value(fwd->descs[offset]);
 }
 
 static int gpio_fwd_get_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,
@@ -293,7 +294,10 @@ static int gpio_fwd_get_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,
 	for_each_set_bit(i, mask, fwd->chip.ngpio)
 		descs[j++] = fwd->descs[i];
 
-	error = gpiod_get_array_value(j, descs, NULL, values);
+	if (fwd->chip.can_sleep)
+		error = gpiod_get_array_value_cansleep(j, descs, NULL, values);
+	else
+		error = gpiod_get_array_value(j, descs, NULL, values);
 	if (error)
 		return error;
 
@@ -328,7 +332,10 @@ static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
 {
 	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
 
-	gpiod_set_value(fwd->descs[offset], value);
+	if (chip->can_sleep)
+		gpiod_set_value_cansleep(fwd->descs[offset], value);
+	else
+		gpiod_set_value(fwd->descs[offset], value);
 }
 
 static void gpio_fwd_set_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,
@@ -343,7 +350,10 @@ static void gpio_fwd_set_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,
 		descs[j++] = fwd->descs[i];
 	}
 
-	gpiod_set_array_value(j, descs, NULL, values);
+	if (fwd->chip.can_sleep)
+		gpiod_set_array_value_cansleep(j, descs, NULL, values);
+	else
+		gpiod_set_array_value(j, descs, NULL, values);
 }
 
 static void gpio_fwd_set_multiple_locked(struct gpio_chip *chip,
-- 
2.25.1