gpio: don't set label from irq helpers

We will soon serialize access to the descriptor label using SRCU. The
write-side of the protection will require calling synchronize_srcu()
which must not be called from atomic context. We have two irq helpers:
gpiochip_lock_as_irq() and gpiochip_unlock_as_irq() that set the label
if the GPIO is not requested but is being used as interrupt. They are
called with a spinlock held from the interrupt subsystem.

They must not do it if we are to use SRCU so instead let's move the
special corner case to a dedicated getter.

Don't actually set the label to "interrupt" in the above case but rather
use the newly added gpiod_get_label() helper to hide the logic that
atomically checks the descriptor flags and returns the address of a
static "interrupt" string.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index c014404c3bed4f0bf087e85eac8ee06f9723ad8b..79717776be84fe30c350a0f7e2d2567b904e7834 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -107,7 +107,14 @@ static bool gpiolib_initialized;
 
 const char *gpiod_get_label(struct gpio_desc *desc)
 {
-       return desc->label;
+       unsigned long flags;
+
+       flags = READ_ONCE(desc->flags);
+       if (test_bit(FLAG_USED_AS_IRQ, &flags) &&
+           !test_bit(FLAG_REQUESTED, &flags))
+               return "interrupt";
+
+       return test_bit(FLAG_REQUESTED, &flags) ? desc->label : NULL;
 }
 
 static inline void desc_set_label(struct gpio_desc *d, const char *label)
@@ -3599,14 +3606,6 @@ int gpiochip_lock_as_irq(struct gpio_chip *gc, unsigned int offset)
        set_bit(FLAG_USED_AS_IRQ, &desc->flags);
        set_bit(FLAG_IRQ_IS_ENABLED, &desc->flags);
 
-       /*
-        * If the consumer has not set up a label (such as when the
-        * IRQ is referenced from .to_irq()) we set up a label here
-        * so it is clear this is used as an interrupt.
-        */
-       if (!desc->label)
-               desc_set_label(desc, "interrupt");
-
        return 0;
 }
 EXPORT_SYMBOL_GPL(gpiochip_lock_as_irq);
@@ -3629,10 +3628,6 @@ void gpiochip_unlock_as_irq(struct gpio_chip *gc, unsigned int offset)
 
        clear_bit(FLAG_USED_AS_IRQ, &desc->flags);
        clear_bit(FLAG_IRQ_IS_ENABLED, &desc->flags);
-
-       /* If we only had this marking, erase it */
-       if (desc->label && !strcmp(desc->label, "interrupt"))
-               desc_set_label(desc, NULL);
 }
 EXPORT_SYMBOL_GPL(gpiochip_unlock_as_irq);