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* [rfc, rft, PATCH v1 1/1] gpio: aggregator: Introduce delay support for individual output pins
@ 2023-06-08 16:21 Andy Shevchenko
  2023-06-08 19:32 ` kernel test robot
                   ` (4 more replies)
  0 siblings, 5 replies; 9+ messages in thread
From: Andy Shevchenko @ 2023-06-08 16:21 UTC (permalink / raw)
  To: Andy Shevchenko, linux-gpio, linux-kernel
  Cc: Geert Uytterhoeven, Linus Walleij, Bartosz Golaszewski,
	Andy Shevchenko, Alexander Stein

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 signal delay line. Intdoduce support of it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---

I don't like the idea of gpio-delay or similar. We have already GPIO
aggregator that incorporates the GPIO proxy / forwarder functionality.

This one is RFC because:
1) just compile tested;
2) has obvious issues with CONFIG_OF_GPIO;
3) contains ~5 patches in a single change for now;
4) requires additional work with blocking sysfs for this;
5) requires some DT bindings work;
6) ...whatever I forgot...

Any comments are appreciated, and tests are esp. welcome!

 drivers/gpio/gpio-aggregator.c | 84 ++++++++++++++++++++++++++++++----
 1 file changed, 74 insertions(+), 10 deletions(-)

diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
index 20a686f12df7..802d123f0188 100644
--- a/drivers/gpio/gpio-aggregator.c
+++ b/drivers/gpio/gpio-aggregator.c
@@ -10,12 +10,14 @@
 #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/module.h>
 #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>
@@ -239,6 +241,11 @@ static void __exit gpio_aggregator_remove_all(void)
  *  GPIO Forwarder
  */
 
+struct gpiochip_fwd_timing {
+	unsigned long ramp_up_us;
+	unsigned long ramp_down_us;
+};
+
 struct gpiochip_fwd {
 	struct gpio_chip chip;
 	struct gpio_desc **descs;
@@ -246,6 +253,7 @@ struct gpiochip_fwd {
 		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 */
 };
 
@@ -333,11 +341,28 @@ static int gpio_fwd_get_multiple_locked(struct gpio_chip *chip,
 static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
 {
 	struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+	const struct gpiochip_fwd_timing *delay_timings;
+	struct gpio_desc *desc = fwd->descs[offset];
+	bool is_active_low = gpiod_is_active_low(desc);
+	bool ramp_up;
 
-	if (chip->can_sleep)
-		gpiod_set_value_cansleep(fwd->descs[offset], value);
-	else
-		gpiod_set_value(fwd->descs[offset], value);
+	delay_timings = &fwd->delay_timings[offset];
+	ramp_up = (!is_active_low && value) || (is_active_low && !value);
+	if (chip->can_sleep) {
+		gpiod_set_value_cansleep(desc, value);
+
+		if (ramp_up && delay_timings->ramp_up_us)
+			fsleep(delay_timings->ramp_up_us);
+		if (!ramp_up && delay_timings->ramp_down_us)
+			fsleep(delay_timings->ramp_down_us);
+	} else {
+		gpiod_set_value(desc, value);
+
+		if (ramp_up && delay_timings->ramp_up_us)
+			udelay(delay_timings->ramp_up_us);
+		if (!ramp_up && delay_timings->ramp_down_us)
+			udelay(delay_timings->ramp_down_us);
+	}
 }
 
 static void gpio_fwd_set_multiple(struct gpiochip_fwd *fwd, unsigned long *mask,
@@ -390,6 +415,28 @@ static int gpio_fwd_to_irq(struct gpio_chip *chip, unsigned int offset)
 	return gpiod_to_irq(fwd->descs[offset]);
 }
 
+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;
+}
+
 /**
  * gpiochip_fwd_create() - Create a new GPIO forwarder
  * @dev: Parent device pointer
@@ -397,6 +444,7 @@ static int gpio_fwd_to_irq(struct gpio_chip *chip, unsigned int offset)
  * @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.
+ * @delay: True if the pins have an external delay line.
  *
  * This function creates a new gpiochip, which forwards all GPIO operations to
  * the passed GPIO descriptors.
@@ -406,7 +454,8 @@ 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[],
+						bool delay)
 {
 	const char *label = dev_name(dev);
 	struct gpiochip_fwd *fwd;
@@ -459,6 +508,17 @@ static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
 	else
 		spin_lock_init(&fwd->slock);
 
+	if (delay) {
+		fwd->delay_timings = devm_kcalloc(dev, ngpios,
+						  sizeof(*fwd->delay_timings),
+						  GFP_KERNEL);
+		if (!fwd->delay_timings)
+			return ERR_PTR(-ENOMEM);
+
+		chip->of_xlate = gpiochip_fwd_delay_of_xlate;
+		chip->of_gpio_n_cells = 3;
+	}
+
 	error = devm_gpiochip_add_data(dev, chip, fwd);
 	if (error)
 		return ERR_PTR(error);
@@ -476,6 +536,7 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct gpio_desc **descs;
 	struct gpiochip_fwd *fwd;
+	bool delay;
 	int i, n;
 
 	n = gpiod_count(dev, NULL);
@@ -492,7 +553,9 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 			return PTR_ERR(descs[i]);
 	}
 
-	fwd = gpiochip_fwd_create(dev, n, descs);
+	delay = fwnode_device_is_compatible(dev_fwnode(dev), "gpio-delay");
+
+	fwd = gpiochip_fwd_create(dev, n, descs, delay);
 	if (IS_ERR(fwd))
 		return PTR_ERR(fwd);
 
@@ -500,23 +563,24 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_OF
 static const struct of_device_id gpio_aggregator_dt_ids[] = {
 	/*
 	 * Add GPIO-operated devices controlled from userspace below,
-	 * or use "driver_override" in sysfs
+	 * or use "driver_override" in sysfs.
 	 */
+	{
+		.compatible = "gpio-delay",
+	},
 	{}
 };
 MODULE_DEVICE_TABLE(of, gpio_aggregator_dt_ids);
-#endif
 
 static struct platform_driver gpio_aggregator_driver = {
 	.probe = gpio_aggregator_probe,
 	.driver = {
 		.name = DRV_NAME,
 		.groups = gpio_aggregator_groups,
-		.of_match_table = of_match_ptr(gpio_aggregator_dt_ids),
+		.of_match_table = gpio_aggregator_dt_ids,
 	},
 };
 
-- 
2.40.0.1.gaa8946217a0b


^ permalink raw reply related	[flat|nested] 9+ messages in thread
end of thread, other threads:[~2023-06-12 17:36 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-06-08 16:21 [rfc, rft, PATCH v1 1/1] gpio: aggregator: Introduce delay support for individual output pins Andy Shevchenko
2023-06-08 19:32 ` kernel test robot
2023-06-08 19:43 ` kernel test robot
2023-06-09  6:40 ` Alexander Stein
2023-06-12 17:30   ` Andy Shevchenko
2023-06-09  7:11 ` Geert Uytterhoeven
2023-06-12 17:32   ` Andy Shevchenko
2023-06-09  7:50 ` Linus Walleij
2023-06-12 17:34   ` Andy Shevchenko

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