gpio: aggregator: Set up a parser of delay line parameters

The aggregator mode can also handle properties of the platform,
that do not belong to the GPIO controller itself. One of such
a property is a signal delay line. Set up a parser to support it.

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

@@ -18,6 +18,7 @@
 #include <linux/mutex.h>
 #include <linux/overflow.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
@@ -422,13 +423,67 @@ static int gpio_fwd_to_irq(struct gpio_chip *chip, unsigned int offset)
 	return gpiod_to_irq(fwd->descs[offset]);
 }
 
+/*
+ * The GPIO delay provides a way to configure platform specific delays
+ * for the GPIO ramp-up or ramp-down delays. This can serve the following
+ * purposes:
+ *   - Open-drain output using an RC filter
+ */
+#define FWD_FEATURE_DELAY		BIT(0)
+
+#ifdef CONFIG_OF_GPIO
+static int gpiochip_fwd_delay_of_xlate(struct gpio_chip *chip,
+				       const struct of_phandle_args *gpiospec,
+				       u32 *flags)
+{
+	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+	struct gpiochip_fwd_timing *timings;
+	u32 line;
+
+	if (gpiospec->args_count != chip->of_gpio_n_cells)
+		return -EINVAL;
+
+	line = gpiospec->args[0];
+	if (line >= chip->ngpio)
+		return -EINVAL;
+
+	timings = &fwd->delay_timings[line];
+	timings->ramp_up_us = gpiospec->args[1];
+	timings->ramp_down_us = gpiospec->args[2];
+
+	return line;
+}
+
+static int gpiochip_fwd_setup_delay_line(struct device *dev, struct gpio_chip *chip,
+					 struct gpiochip_fwd *fwd)
+{
+	fwd->delay_timings = devm_kcalloc(dev, chip->ngpio,
+					  sizeof(*fwd->delay_timings),
+					  GFP_KERNEL);
+	if (!fwd->delay_timings)
+		return -ENOMEM;
+
+	chip->of_xlate = gpiochip_fwd_delay_of_xlate;
+	chip->of_gpio_n_cells = 3;
+
+	return 0;
+}
+#else
+static int gpiochip_fwd_setup_delay_line(struct device *dev, struct gpio_chip *chip,
+					 struct gpiochip_fwd *fwd)
+{
+	return 0;
+}
+#endif	/* !CONFIG_OF_GPIO */
+
 /**
  * gpiochip_fwd_create() - Create a new GPIO forwarder
  * @dev: Parent device pointer
  * @ngpios: Number of GPIOs in the forwarder.
  * @descs: Array containing the GPIO descriptors to forward to.
  *         This array must contain @ngpios entries, and must not be deallocated
  *         before the forwarder has been destroyed again.
+ * @features: Bitwise ORed features as defined with FWD_FEATURE_*.
  *
  * This function creates a new gpiochip, which forwards all GPIO operations to
  * the passed GPIO descriptors.
@@ -438,7 +493,8 @@ static int gpio_fwd_to_irq(struct gpio_chip *chip, unsigned int offset)
  */
 static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
 						unsigned int ngpios,
-						struct gpio_desc *descs[])
+						struct gpio_desc *descs[],
+						unsigned long features)
 {
 	const char *label = dev_name(dev);
 	struct gpiochip_fwd *fwd;
@@ -491,6 +547,12 @@ static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
 	else
 		spin_lock_init(&fwd->slock);
 
+	if (features & FWD_FEATURE_DELAY) {
+		error = gpiochip_fwd_setup_delay_line(dev, chip, fwd);
+		if (error)
+			return ERR_PTR(error);
+	}
+
 	error = devm_gpiochip_add_data(dev, chip, fwd);
 	if (error)
 		return ERR_PTR(error);
@@ -508,6 +570,7 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct gpio_desc **descs;
 	struct gpiochip_fwd *fwd;
+	unsigned long features;
 	int i, n;
 
 	n = gpiod_count(dev, NULL);
@@ -524,7 +587,8 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 			return PTR_ERR(descs[i]);
 	}
 
-	fwd = gpiochip_fwd_create(dev, n, descs);
+	features = (uintptr_t)device_get_match_data(dev);
+	fwd = gpiochip_fwd_create(dev, n, descs, features);
 	if (IS_ERR(fwd))
 		return PTR_ERR(fwd);
 
@@ -533,6 +597,10 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 }
 
 static const struct of_device_id gpio_aggregator_dt_ids[] = {
+	{
+		.compatible = "gpio-delay",
+		.data = (void *)FWD_FEATURE_DELAY,
+	},
 	/*
 	 * Add GPIO-operated devices controlled from userspace below,
 	 * or use "driver_override" in sysfs.