This driver implements a GPIO enable/disable delay. It supports a list
of GPIO outputs, which ramp-up/ramp-down delay can be specified at
consumer location.
The main purpose is to address external, passive delays upon line
voltage changes.
Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>
---
drivers/gpio/Kconfig | 8 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-delay.c | 164 ++++++++++++++++++++++++++++++++++++++
3 files changed, 173 insertions(+)
create mode 100644 drivers/gpio/gpio-delay.c
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index ec7cfd4f52b1..8f1dcbe3fd00 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1684,6 +1684,14 @@ config GPIO_AGGREGATOR
industrial control context, to be operated from userspace using
the GPIO chardev interface.
+config GPIO_DELAY
+ tristate "GPIO delay"
+ help
+ Say yes here to enable the GPIO delay, which provides a way to
+ configure platform specific delays for GPIO ramp-up or ramp-down
+ delays. This can serve the following purposes:
+ - Open-drain output using an RC filter
+
config GPIO_LATCH
tristate "GPIO latch driver"
help
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 010587025fc8..56b6cbe35248 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_GPIO_DA9052) += gpio-da9052.o
obj-$(CONFIG_GPIO_DA9055) += gpio-da9055.o
obj-$(CONFIG_GPIO_DAVINCI) += gpio-davinci.o
obj-$(CONFIG_GPIO_DLN2) += gpio-dln2.o
+obj-$(CONFIG_GPIO_DELAY) += gpio-delay.o
obj-$(CONFIG_GPIO_DWAPB) += gpio-dwapb.o
obj-$(CONFIG_GPIO_EIC_SPRD) += gpio-eic-sprd.o
obj-$(CONFIG_GPIO_EM) += gpio-em.o
diff --git a/drivers/gpio/gpio-delay.c b/drivers/gpio/gpio-delay.c
new file mode 100644
index 000000000000..a91d2ea9a8bc
--- /dev/null
+++ b/drivers/gpio/gpio-delay.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2022 TQ-Systems GmbH
+ * Author: Alexander Stein <linux@xxxxxxxxxxxxxxx>
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/delay.h>
+
+#include "gpiolib.h"
+
+struct gpio_delay_timing {
+ unsigned long ramp_up_delay_us;
+ unsigned long ramp_down_delay_us;
+};
+
+struct gpio_delay_priv {
+ struct gpio_chip gc;
+ struct gpio_descs *input_gpio;
+ struct gpio_delay_timing *delay_timings;
+};
+
+static int gpio_delay_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+ return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void gpio_delay_set(struct gpio_chip *gc, unsigned int offset, int val)
+{
+ struct gpio_delay_priv *priv = gpiochip_get_data(gc);
+ struct gpio_desc *gpio_desc = priv->input_gpio->desc[offset];
+ const struct gpio_delay_timing *delay_timings;
+ bool ramp_up;
+
+ gpiod_set_value(gpio_desc, val);
+
+ delay_timings = &priv->delay_timings[offset];
+ ramp_up = (!gpiod_is_active_low(gpio_desc) && val) ||
+ (gpiod_is_active_low(gpio_desc) && !val);
+
+ if (ramp_up && delay_timings->ramp_up_delay_us)
+ udelay(delay_timings->ramp_up_delay_us);
+ if (!ramp_up && delay_timings->ramp_down_delay_us)
+ udelay(delay_timings->ramp_down_delay_us);
+}
+
+static void gpio_delay_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
+{
+ struct gpio_delay_priv *priv = gpiochip_get_data(gc);
+ struct gpio_desc *gpio_desc = priv->input_gpio->desc[offset];
+ const struct gpio_delay_timing *delay_timings;
+ bool ramp_up;
+
+ gpiod_set_value_cansleep(gpio_desc, val);
+
+ delay_timings = &priv->delay_timings[offset];
+ ramp_up = (!gpiod_is_active_low(gpio_desc) && val) ||
+ (gpiod_is_active_low(gpio_desc) && !val);
+
+ if (ramp_up && delay_timings->ramp_up_delay_us)
+ fsleep(delay_timings->ramp_up_delay_us);
+ if (!ramp_up && delay_timings->ramp_down_delay_us)
+ fsleep(delay_timings->ramp_down_delay_us);
+}
+
+static int gpio_delay_of_xlate(struct gpio_chip *gc,
+ const struct of_phandle_args *gpiospec,
+ u32 *flags)
+{
+ struct gpio_delay_priv *priv = gpiochip_get_data(gc);
+ struct gpio_delay_timing *timings;
+ u32 line;
+
+ if (gpiospec->args_count != gc->of_gpio_n_cells)
+ return -EINVAL;
+
+ line = gpiospec->args[0];
+ if (line >= gc->ngpio)
+ return -EINVAL;
+
+ timings = &priv->delay_timings[line];
+ timings->ramp_up_delay_us = gpiospec->args[1];
+ timings->ramp_down_delay_us = gpiospec->args[2];
+
+ return line;
+}
+
+static bool gpio_delay_can_sleep(const struct gpio_delay_priv *priv)
+{
+ int i;
+
+ for (i = 0; i < priv->input_gpio->ndescs; i++)
+ if (gpiod_cansleep(priv->input_gpio->desc[i]))
+ return true;
+
+ return false;
+}
+
+static int gpio_delay_probe(struct platform_device *pdev)
+{
+ struct gpio_delay_priv *priv;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->input_gpio = devm_gpiod_get_array(&pdev->dev, "input", GPIOD_OUT_LOW);
+ if (IS_ERR(priv->input_gpio))
+ return dev_err_probe(&pdev->dev, PTR_ERR(priv->input_gpio),
+ "Failed to get input-gpios");
+
+ priv->delay_timings = devm_kcalloc(&pdev->dev,
+ priv->input_gpio->ndescs,
+ sizeof(*priv->delay_timings),
+ GFP_KERNEL);
+ if (!priv->delay_timings)
+ return -ENOMEM;
+
+ if (gpio_delay_can_sleep(priv)) {
+ priv->gc.can_sleep = true;
+ priv->gc.set = gpio_delay_set_can_sleep;
+ } else {
+ priv->gc.can_sleep = false;
+ priv->gc.set = gpio_delay_set;
+ }
+
+ priv->gc.get_direction = gpio_delay_get_direction;
+ priv->gc.of_xlate = gpio_delay_of_xlate;
+ priv->gc.of_gpio_n_cells = 3;
+ priv->gc.ngpio = priv->input_gpio->ndescs;
+ priv->gc.owner = THIS_MODULE;
+ priv->gc.base = -1;
+ priv->gc.parent = &pdev->dev;
+
+ platform_set_drvdata(pdev, priv);
+
+ return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
+}
+
+static const struct of_device_id gpio_delay_ids[] = {
+ {
+ .compatible = "gpio-delay",
+ },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, gpio_delay_ids);
+
+static struct platform_driver gpio_delay_driver = {
+ .driver = {
+ .name = "gpio-delay",
+ .of_match_table = gpio_delay_ids,
+ },
+ .probe = gpio_delay_probe,
+};
+module_platform_driver(gpio_delay_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("GPIO delay driver");
--
2.34.1
