gpio: Add GPIO delay driver

Add a GPIO controller driver that provides configurable delays when
setting GPIO output values. This is useful for hardware that requires
specific timing delays during power sequencing or GPIO state changes.

The driver wraps underlying GPIO controllers and adds programmable
ramp-up and ramp-down delays specified in microseconds through the
device tree. Each GPIO can have independent delay timings.

Device tree binding matches Linux.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/575998efc6ba0e405640789cf8d05f0b633f496e.1770105146.git.michal.simek@amd.com

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 60c5c54688e64be4704c108f9e1d3103b32c54e5..f69919abc05b65f7f2d99eb26c2fd9b35f5ffabb 100644 (file)
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1,3 +1,11 @@
+config GPIO_DELAY
+       bool "GPIO delay driver"
+       depends on DM_GPIO
+       help
+         Enable the GPIO delay driver.
+         This driver allows wrapping another GPIO controller and inserting
+         ramp-up/ramp-down delays on output changes, as described in the
+         Linux gpio-delay binding.
 #
 # GPIO infrastructure and drivers
 #

diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 910478c0c7a9fa3ef5be45e0a0d1bc63643b63de..fec258f59f52d1348424572a07442de01c8ea622 100644 (file)
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_ATMEL_PIO4)      += atmel_pio4.o
 obj-$(CONFIG_BCM6345_GPIO)     += bcm6345_gpio.o
 obj-$(CONFIG_CORTINA_GPIO)      += cortina_gpio.o
 obj-$(CONFIG_FXL6408_GPIO)     += gpio-fxl6408.o
+obj-$(CONFIG_GPIO_DELAY)       += gpio-delay.o
 obj-$(CONFIG_INTEL_GPIO)       += intel_gpio.o
 obj-$(CONFIG_INTEL_ICH6_GPIO)  += intel_ich6_gpio.o
 obj-$(CONFIG_INTEL_BROADWELL_GPIO)     += intel_broadwell_gpio.o

diff --git a/drivers/gpio/gpio-delay.c b/drivers/gpio/gpio-delay.c
new file mode 100644 (file)
index 0000000..9105dee
--- /dev/null
+++ b/drivers/gpio/gpio-delay.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 - 2026, Advanced Micro Devices, Inc.
+ *
+ * Michal Simek <michal.simek@amd.com>
+ */
+
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <dm/devres.h>
+#include <asm/gpio.h>
+#include <linux/delay.h>
+
+struct gpio_delay_desc {
+       struct gpio_desc real_gpio;
+       u32 ramp_up_us;
+       u32 ramp_down_us;
+};
+
+struct gpio_delay_priv {
+       struct gpio_delay_desc *descs;
+};
+
+static int gpio_delay_direction_input(struct udevice *dev, unsigned int offset)
+{
+       return -ENOSYS;
+}
+
+static int gpio_delay_get_value(struct udevice *dev, unsigned int offset)
+{
+       return -ENOSYS;
+}
+
+static int gpio_delay_set_value(struct udevice *dev, unsigned int offset,
+                               int value)
+{
+       struct gpio_delay_priv *priv = dev_get_priv(dev);
+       struct gpio_delay_desc *desc = &priv->descs[offset];
+       u32 wait;
+       int ret;
+
+       dev_dbg(dev, "gpio %d set to %d\n", offset, value);
+
+       ret = dm_gpio_set_value(&desc->real_gpio, value);
+       if (ret) {
+               dev_err(dev, "Failed to set gpio %d, value %d\n", offset, value);
+               return ret;
+       }
+
+       if (value)
+               wait = desc->ramp_up_us;
+       else
+               wait = desc->ramp_down_us;
+
+       udelay(wait);
+
+       dev_dbg(dev, "waited for %d us\n", wait);
+
+       return 0;
+}
+
+static int gpio_delay_direction_output(struct udevice *dev, unsigned int offset,
+                                      int value)
+{
+       return gpio_delay_set_value(dev, offset, value);
+}
+
+static int gpio_delay_xlate(struct udevice *dev, struct gpio_desc *desc,
+                           struct ofnode_phandle_args *args)
+{
+       struct gpio_delay_priv *priv = dev_get_priv(dev);
+
+       if (args->args_count < 3)
+               return -EINVAL;
+
+       if (args->args[0] >= 32)
+               return -EINVAL;
+
+       struct gpio_delay_desc *d = &priv->descs[args->args[0]];
+
+       d->ramp_up_us = args->args[1];
+       d->ramp_down_us = args->args[2];
+
+       dev_dbg(dev, "pin: %d, ramp_up_us: %d, ramp_down_us: %d\n",
+               args->args[0], d->ramp_up_us, d->ramp_down_us);
+
+       return 0;
+}
+
+static const struct dm_gpio_ops gpio_delay_ops = {
+       .direction_output = gpio_delay_direction_output,
+       .direction_input = gpio_delay_direction_input,
+       .get_value = gpio_delay_get_value,
+       .set_value = gpio_delay_set_value,
+       .xlate = gpio_delay_xlate,
+};
+
+static int gpio_delay_probe(struct udevice *dev)
+{
+       struct gpio_delay_priv *priv = dev_get_priv(dev);
+       struct gpio_delay_desc *d;
+       ofnode node = dev_ofnode(dev);
+       int i = 0, ret, ngpio;
+
+       ngpio = gpio_get_list_count(dev, "gpios");
+       if (ngpio < 0)
+               return ngpio;
+
+       dev_dbg(dev, "gpios: %d\n", ngpio);
+
+       priv->descs = devm_kmalloc_array(dev, ngpio, sizeof(*d), GFP_KERNEL);
+       if (!priv->descs)
+               return -ENOMEM;
+
+       /* Request all GPIOs described in the controller node */
+       for (i = 0; i < ngpio; i++) {
+               d = &priv->descs[i];
+               ret = gpio_request_by_name_nodev(node, "gpios", i,
+                                                &d->real_gpio, 0);
+               if (ret)
+                       return ret;
+       }
+
+       return 0;
+}
+
+static const struct udevice_id gpio_delay_ids[] = {
+       { .compatible = "gpio-delay" },
+       { }
+};
+
+U_BOOT_DRIVER(gpio_delay) = {
+       .name = "gpio-delay",
+       .id = UCLASS_GPIO,
+       .of_match = gpio_delay_ids,
+       .ops = &gpio_delay_ops,
+       .priv_auto = sizeof(struct gpio_delay_priv),
+       .probe = gpio_delay_probe,
+};