gpio: aggregator: Support delay for setting up individual GPIOs

In some cases the GPIO may require an additional delay after setting
its value. Add support for that into the GPIO forwarder code.

This will be fully enabled for use in the following changes.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: andy-shev

drivers/gpio/gpio-aggregator.c

@@ -10,6 +10,7 @@
 #include <linux/bitmap.h>
 #include <linux/bitops.h>
 #include <linux/ctype.h>
+#include <linux/delay.h>
 #include <linux/idr.h>
 #include <linux/kernel.h>
 #include <linux/mod_devicetable.h>
@@ -240,13 +241,19 @@ static void __exit gpio_aggregator_remove_all(void)
  *  GPIO Forwarder
  */
 
+struct gpiochip_fwd_timing {
+	u32 ramp_up_us;
+	u32 ramp_down_us;
+};
+
 struct gpiochip_fwd {
 	struct gpio_chip chip;
 	struct gpio_desc **descs;
 	union {
 		struct mutex mlock;	/* protects tmp[] if can_sleep */
 		spinlock_t slock;	/* protects tmp[] if !can_sleep */
 	};
+	struct gpiochip_fwd_timing *delay_timings;
 	unsigned long tmp[];		/* values and descs for multiple ops */
 };
 
@@ -331,6 +338,27 @@ static int gpio_fwd_get_multiple_locked(struct gpio_chip *chip,
 	return error;
 }
 
+static void gpio_fwd_delay(struct gpio_chip *chip, unsigned int offset, int value)
+{
+	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+	const struct gpiochip_fwd_timing *delay_timings;
+	bool is_active_low = gpiod_is_active_low(fwd->descs[offset]);
+	u32 delay_us;
+
+	delay_timings = &fwd->delay_timings[offset];
+	if ((!is_active_low && value) || (is_active_low && !value))
+		delay_us = delay_timings->ramp_up_us;
+	else
+		delay_us = delay_timings->ramp_down_us;
+	if (!delay_us)
+		return;
+
+	if (chip->can_sleep)
+		fsleep(delay_us);
+	else
+		udelay(delay_us);
+}
+
 static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
 {
 	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
@@ -339,6 +367,9 @@ static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
 		gpiod_set_value_cansleep(fwd->descs[offset], value);
 	else
 		gpiod_set_value(fwd->descs[offset], value);
+
+	if (fwd->delay_timings)
+		gpio_fwd_delay(chip, offset, value);
 }
 
 static void gpio_fwd_set_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,