gpio: rcar: Fine-grained Runtime PM support

Currently gpio modules are runtime-resumed at probe time. This means the
gpio module will be active all the time (except during system suspend,
if not configured as a wake-up source).

While an R-Car Gen2 gpio module retains pins configured for output at
the requested level while put in standby mode, gpio registercannot be
accessed while suspended.  Unfortunately pm_runtime_get_sync() cannot be
called from all contexts where gpio register access is needed. Hence
move the Runtime PM handling from probe/remove time to gpio request/free
time, which is probably the best we can do.

On r8a7791/koelsch, gpio modules 0, 1, 3, and 4 are now suspended during
normal use (gpio2 is used for LEDs and regulators, gpio5 for keys, gpio6
for SD-Card CD & WP, gpio7 for keys and regulators).
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-rcar.c

@@ -251,17 +251,32 @@ static void gpio_rcar_config_general_input_output_mode(struct gpio_chip *chip,
 
 static int gpio_rcar_request(struct gpio_chip *chip, unsigned offset)
 {
-	return pinctrl_request_gpio(chip->base + offset);
+	struct gpio_rcar_priv *p = gpio_to_priv(chip);
+	int error;
+
+	error = pm_runtime_get_sync(&p->pdev->dev);
+	if (error < 0)
+		return error;
+
+	error = pinctrl_request_gpio(chip->base + offset);
+	if (error)
+		pm_runtime_put(&p->pdev->dev);
+
+	return error;
 }
 
 static void gpio_rcar_free(struct gpio_chip *chip, unsigned offset)
 {
+	struct gpio_rcar_priv *p = gpio_to_priv(chip);
+
 	pinctrl_free_gpio(chip->base + offset);
 
 	/* Set the GPIO as an input to ensure that the next GPIO request won't
 	 * drive the GPIO pin as an output.
 	 */
 	gpio_rcar_config_general_input_output_mode(chip, offset, false);
+
+	pm_runtime_put(&p->pdev->dev);
 }
 
 static int gpio_rcar_direction_input(struct gpio_chip *chip, unsigned offset)
@@ -405,7 +420,6 @@ static int gpio_rcar_probe(struct platform_device *pdev)
 	}
 
 	pm_runtime_enable(dev);
-	pm_runtime_get_sync(dev);
 
 	io = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
@@ -487,7 +501,6 @@ static int gpio_rcar_probe(struct platform_device *pdev)
 err1:
 	gpiochip_remove(gpio_chip);
 err0:
-	pm_runtime_put(dev);
 	pm_runtime_disable(dev);
 	return ret;
 }
@@ -498,7 +511,6 @@ static int gpio_rcar_remove(struct platform_device *pdev)
 
 	gpiochip_remove(&p->gpio_chip);
 
-	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	return 0;
 }