gpio: Add gpio delay driver

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@ew.tq-group.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index a470ec8d617ba8ef92234c4395a3cde43b32191f..d45b55bef2e37889bc49ebe14b1dd9711935bc61 100644 (file)
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1733,6 +1733,14 @@ 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 20036af3acb1db364ebfeb50790b3e76a2c713d6..abb6ead17d834dd3df68506d0d3afbcde91f8b21 100644 (file)
--- 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_ELKHARTLAKE)         += gpio-elkhartlake.o

diff --git a/drivers/gpio/gpio-delay.c b/drivers/gpio/gpio-delay.c
new file mode 100644 (file)
index 0000000..b489b56
--- /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@ew.tq-group.com>
+ */
+
+#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, NULL, 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@ew.tq-group.com>");
+MODULE_DESCRIPTION("GPIO delay driver");