gpio: gpiolib: Allow GPIO IRQs to lazy disable

With 'commit 461c1a7 ("gpiolib: override irq_enable/disable")' gpiolib
overrides irqchip's irq_enable and irq_disable callbacks. If irq_disable
callback is implemented then genirq takes unlazy path to disable irq.

Underlying irqchip may not want to implement irq_disable callback to lazy
disable irq when client drivers invokes disable_irq(). By overriding
irq_disable callback, gpiolib ends up always unlazy disabling IRQ.

Allow gpiolib to lazy disable IRQs by overriding irq_disable callback only
if irqchip implemented irq_disable. In cases where irq_disable is not
implemented irq_mask is overridden. Similarly override irq_enable callback
only if irqchip implemented irq_enable otherwise irq_unmask is overridden.

Fixes: 461c1a7 ("gpiolib: override irq_enable/disable")
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Link: https://lore.kernel.org/r/1590253873-11556-2-git-send-email-mkshah@codeaurora.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -2471,32 +2471,37 @@ static void gpiochip_irq_relres(struct irq_data *d)
 	gpiochip_relres_irq(gc, d->hwirq);
 }
 
+static void gpiochip_irq_mask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+
+	if (gc->irq.irq_mask)
+		gc->irq.irq_mask(d);
+	gpiochip_disable_irq(gc, d->hwirq);
+}
+
+static void gpiochip_irq_unmask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+
+	gpiochip_enable_irq(gc, d->hwirq);
+	if (gc->irq.irq_unmask)
+		gc->irq.irq_unmask(d);
+}
+
 static void gpiochip_irq_enable(struct irq_data *d)
 {
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
 
 	gpiochip_enable_irq(gc, d->hwirq);
-	if (gc->irq.irq_enable)
-		gc->irq.irq_enable(d);
-	else
-		gc->irq.chip->irq_unmask(d);
+	gc->irq.irq_enable(d);
 }
 
 static void gpiochip_irq_disable(struct irq_data *d)
 {
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
 
-	/*
-	 * Since we override .irq_disable() we need to mimic the
-	 * behaviour of __irq_disable() in irq/chip.c.
-	 * First call .irq_disable() if it exists, else mimic the
-	 * behaviour of mask_irq() which calls .irq_mask() if
-	 * it exists.
-	 */
-	if (gc->irq.irq_disable)
-		gc->irq.irq_disable(d);
-	else if (gc->irq.chip->irq_mask)
-		gc->irq.chip->irq_mask(d);
+	gc->irq.irq_disable(d);
 	gpiochip_disable_irq(gc, d->hwirq);
 }
 
@@ -2521,10 +2526,22 @@ static void gpiochip_set_irq_hooks(struct gpio_chip *gc)
 			  "detected irqchip that is shared with multiple gpiochips: please fix the driver.\n");
 		return;
 	}
-	gc->irq.irq_enable = irqchip->irq_enable;
-	gc->irq.irq_disable = irqchip->irq_disable;
-	irqchip->irq_enable = gpiochip_irq_enable;
-	irqchip->irq_disable = gpiochip_irq_disable;
+
+	if (irqchip->irq_disable) {
+		gc->irq.irq_disable = irqchip->irq_disable;
+		irqchip->irq_disable = gpiochip_irq_disable;
+	} else {
+		gc->irq.irq_mask = irqchip->irq_mask;
+		irqchip->irq_mask = gpiochip_irq_mask;
+	}
+
+	if (irqchip->irq_enable) {
+		gc->irq.irq_enable = irqchip->irq_enable;
+		irqchip->irq_enable = gpiochip_irq_enable;
+	} else {
+		gc->irq.irq_unmask = irqchip->irq_unmask;
+		irqchip->irq_unmask = gpiochip_irq_unmask;
+	}
 }
 
 /**

include/linux/gpio/driver.h

@@ -253,6 +253,19 @@ struct gpio_irq_chip {
 	 * Store old irq_chip irq_disable callback
 	 */
 	void		(*irq_disable)(struct irq_data *data);
+	/**
+	 * @irq_unmask:
+	 *
+	 * Store old irq_chip irq_unmask callback
+	 */
+	void		(*irq_unmask)(struct irq_data *data);
+
+	/**
+	 * @irq_mask:
+	 *
+	 * Store old irq_chip irq_mask callback
+	 */
+	void		(*irq_mask)(struct irq_data *data);
 };
 
 /**