[PATCH/RFC] gpio: rcar: Add Runtime PM handling for interrupts

[Geert Uytterhoeven <geert+renesas@glider.be>]

The R-Car GPIO driver handles Runtime PM for requested GPIOs only.

When using a GPIO purely as an interrupt source, no Runtime PM handling
is done, and the GPIO module's clock may not be enabled.

To fix this:
  - Add .irq_request_resources() and .irq_release_resources() callbacks
    to handle Runtime PM when an interrupt is requested,
  - Runtime-resume the device before writing to the GPIO module's
    registers for disabling/enabling an interrupt, or for configuring
    the interrupt type,
  - Add checks to warn when the GPIO module's registers are accessed
    while the device is runtime-suspended.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This fixes ravb Ethernet on r8a7795/Salvator-X, which was "broken" by
commit d5c3d84657db57bd ("net: phy: Avoid polling PHY with
PHY_IGNORE_INTERRUPTS").

Does it also fix the HDMI interrupt on r8a7791/Koelsch?

Notes:
  1. I assume gpio_rcar_irq_{dis,en}able() may be called from contexts
     where pm_runtime_get_sync() may not be called.
     However, so far I didn't see any reports from the might_sleep_if()
     check in __pm_runtime_resume(),
  2. gpio_rcar_irq_disable() is called from the IRQ core before
     gpio_rcar_irq_set_type().
     Else an alternative solution could be to just runtime-resume the
     device from gpio_rcar_irq_set_type() when an interrupt is setup,
     and never call pm_runtime_put() again. That would cause issues when
     compiling gpio-rcar as a module, though.
---
 drivers/gpio/gpio-rcar.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
index cf41440aff91971e..63b679b3af5d6d16 100644
--- a/drivers/gpio/gpio-rcar.c
+++ b/drivers/gpio/gpio-rcar.c
@@ -59,12 +59,18 @@ struct gpio_rcar_priv {
 
 static inline u32 gpio_rcar_read(struct gpio_rcar_priv *p, int offs)
 {
+	WARN(pm_runtime_suspended(&p->pdev->dev),
+				  "%s: %s is runtime-suspended\n", __func__,
+				  dev_name(&p->pdev->dev));
 	return ioread32(p->base + offs);
 }
 
 static inline void gpio_rcar_write(struct gpio_rcar_priv *p, int offs,
 				   u32 value)
 {
+	WARN(pm_runtime_suspended(&p->pdev->dev),
+				  "%s: %s is runtime-suspended\n", __func__,
+				  dev_name(&p->pdev->dev));
 	iowrite32(value, p->base + offs);
 }
 
@@ -86,7 +92,11 @@ static void gpio_rcar_irq_disable(struct irq_data *d)
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
 	struct gpio_rcar_priv *p = gpiochip_get_data(gc);
 
+	if (pm_runtime_get_sync(&p->pdev->dev) < 0)
+		return;
+
 	gpio_rcar_write(p, INTMSK, ~BIT(irqd_to_hwirq(d)));
+	pm_runtime_put(&p->pdev->dev);
 }
 
 static void gpio_rcar_irq_enable(struct irq_data *d)
@@ -94,7 +104,11 @@ static void gpio_rcar_irq_enable(struct irq_data *d)
 	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
 	struct gpio_rcar_priv *p = gpiochip_get_data(gc);
 
+	if (pm_runtime_get_sync(&p->pdev->dev) < 0)
+		return;
+
 	gpio_rcar_write(p, MSKCLR, BIT(irqd_to_hwirq(d)));
+	pm_runtime_put(&p->pdev->dev);
 }
 
 static void gpio_rcar_config_interrupt_input_mode(struct gpio_rcar_priv *p,
@@ -105,6 +119,9 @@ static void gpio_rcar_config_interrupt_input_mode(struct gpio_rcar_priv *p,
 {
 	unsigned long flags;
 
+	if (pm_runtime_get_sync(&p->pdev->dev) < 0)
+		return;
+
 	/* follow steps in the GPIO documentation for
 	 * "Setting Edge-Sensitive Interrupt Input Mode" and
 	 * "Setting Level-Sensitive Interrupt Input Mode"
@@ -130,6 +147,8 @@ static void gpio_rcar_config_interrupt_input_mode(struct gpio_rcar_priv *p,
 		gpio_rcar_write(p, INTCLR, BIT(hwirq));
 
 	spin_unlock_irqrestore(&p->lock, flags);
+
+	pm_runtime_put(&p->pdev->dev);
 }
 
 static int gpio_rcar_irq_set_type(struct irq_data *d, unsigned int type)
@@ -196,6 +215,27 @@ static int gpio_rcar_irq_set_wake(struct irq_data *d, unsigned int on)
 	return 0;
 }
 
+static int gpio_rcar_irq_request_resources(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_rcar_priv *p = gpiochip_get_data(gc);
+	int error;
+
+	error = pm_runtime_get_sync(&p->pdev->dev);
+	if (error < 0)
+		return error;
+
+	return 0;
+}
+
+static void gpio_rcar_irq_release_resources(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_rcar_priv *p = gpiochip_get_data(gc);
+
+	pm_runtime_put(&p->pdev->dev);
+}
+
 static irqreturn_t gpio_rcar_irq_handler(int irq, void *dev_id)
 {
 	struct gpio_rcar_priv *p = dev_id;
@@ -450,6 +490,8 @@ static int gpio_rcar_probe(struct platform_device *pdev)
 	irq_chip->irq_unmask = gpio_rcar_irq_enable;
 	irq_chip->irq_set_type = gpio_rcar_irq_set_type;
 	irq_chip->irq_set_wake = gpio_rcar_irq_set_wake;
+	irq_chip->irq_request_resources = gpio_rcar_irq_request_resources;
+	irq_chip->irq_release_resources = gpio_rcar_irq_release_resources;
 	irq_chip->flags	= IRQCHIP_SET_TYPE_MASKED | IRQCHIP_MASK_ON_SUSPEND;
 
 	ret = gpiochip_add_data(gpio_chip, p);
-- 
1.9.1