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From cc09cd9804f681ae3efec1832f2be890d9be467d Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Thu, 14 Oct 2021 11:09:18 +0100
Subject: [PATCH] drivers/gpio: Add a driver that wraps the PWM API as
a GPIO controller
For cases where spare PWM outputs are available, but are desired
to be addressed a standard outputs instead.
Wraps a PWM channel as a new GPIO chip with the one output.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
drivers/gpio/Kconfig | 8 +++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-pwm.c | 144 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 153 insertions(+)
create mode 100644 drivers/gpio/gpio-pwm.c
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -485,6 +485,14 @@ config GPIO_PMIC_EIC_SPRD
help
Say yes here to support Spreadtrum PMIC EIC device.
+config GPIO_PWM
+ tristate "PWM chip GPIO"
+ depends on OF_GPIO
+ depends on PWM
+ help
+ Turn on support for exposing a PWM chip as a GPIO
+ driver.
+
config GPIO_PXA
bool "PXA GPIO support"
depends on ARCH_PXA || ARCH_MMP || COMPILE_TEST
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -122,6 +122,7 @@ obj-$(CONFIG_GPIO_PCI_IDIO_16) += gpio-
obj-$(CONFIG_GPIO_PISOSR) += gpio-pisosr.o
obj-$(CONFIG_GPIO_PL061) += gpio-pl061.o
obj-$(CONFIG_GPIO_PMIC_EIC_SPRD) += gpio-pmic-eic-sprd.o
+obj-$(CONFIG_GPIO_PWM) += gpio-pwm.o
obj-$(CONFIG_GPIO_PXA) += gpio-pxa.o
obj-$(CONFIG_GPIO_RASPBERRYPI_EXP) += gpio-raspberrypi-exp.o
obj-$(CONFIG_GPIO_RC5T583) += gpio-rc5t583.o
--- /dev/null
+++ b/drivers/gpio/gpio-pwm.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * GPIO driver wrapping PWM API
+ *
+ * PWM 0% and PWM 100% are equivalent to digital GPIO
+ * outputs, and there are times where it is useful to use
+ * PWM outputs as straight GPIOs (eg outputs of NXP PCA9685
+ * I2C PWM chip). This driver wraps the PWM API as a GPIO
+ * controller.
+ *
+ * Copyright (C) 2021 Raspberry Pi (Trading) Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+struct pwm_gpio {
+ struct gpio_chip gc;
+ struct pwm_device **pwm;
+};
+
+static int pwm_gpio_get_direction(struct gpio_chip *gc, unsigned int off)
+{
+ return GPIO_LINE_DIRECTION_OUT;
+}
+
+static void pwm_gpio_set(struct gpio_chip *gc, unsigned int off, int val)
+{
+ struct pwm_gpio *pwm_gpio = gpiochip_get_data(gc);
+ struct pwm_state state;
+
+ pwm_get_state(pwm_gpio->pwm[off], &state);
+ state.duty_cycle = val ? state.period : 0;
+ pwm_apply_state(pwm_gpio->pwm[off], &state);
+}
+
+static int pwm_gpio_parse_dt(struct pwm_gpio *pwm_gpio,
+ struct device *dev)
+{
+ struct device_node *node = dev->of_node;
+ struct pwm_state state;
+ int ret = 0, i, num_gpios;
+ const char *pwm_name;
+
+ if (!node)
+ return -ENODEV;
+
+ num_gpios = of_property_count_strings(node, "pwm-names");
+ if (num_gpios <= 0)
+ return 0;
+
+ pwm_gpio->pwm = devm_kzalloc(dev,
+ sizeof(*pwm_gpio->pwm) * num_gpios,
+ GFP_KERNEL);
+ if (!pwm_gpio->pwm)
+ return -ENOMEM;
+
+ for (i = 0; i < num_gpios; i++) {
+ ret = of_property_read_string_index(node, "pwm-names", i,
+ &pwm_name);
+ if (ret) {
+ dev_err(dev, "unable to get pwm device index %d, name %s",
+ i, pwm_name);
+ goto error;
+ }
+
+ pwm_gpio->pwm[i] = devm_pwm_get(dev, pwm_name);
+ if (IS_ERR(pwm_gpio->pwm[i])) {
+ ret = PTR_ERR(pwm_gpio->pwm[i]);
+ if (ret != -EPROBE_DEFER)
+ dev_err(dev, "unable to request PWM\n");
+ goto error;
+ }
+
+ /* Sync up PWM state. */
+ pwm_init_state(pwm_gpio->pwm[i], &state);
+
+ state.duty_cycle = 0;
+ pwm_apply_state(pwm_gpio->pwm[i], &state);
+ }
+
+ pwm_gpio->gc.ngpio = num_gpios;
+
+error:
+ return ret;
+}
+
+static int pwm_gpio_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct pwm_gpio *pwm_gpio;
+ int ret;
+
+ pwm_gpio = devm_kzalloc(dev, sizeof(*pwm_gpio), GFP_KERNEL);
+ if (!pwm_gpio)
+ return -ENOMEM;
+
+ pwm_gpio->gc.parent = dev;
+ pwm_gpio->gc.label = "pwm-gpio";
+ pwm_gpio->gc.owner = THIS_MODULE;
+ pwm_gpio->gc.of_node = dev->of_node;
+ pwm_gpio->gc.base = -1;
+
+ pwm_gpio->gc.get_direction = pwm_gpio_get_direction;
+ pwm_gpio->gc.set = pwm_gpio_set;
+ pwm_gpio->gc.can_sleep = true;
+
+ ret = pwm_gpio_parse_dt(pwm_gpio, dev);
+ if (ret)
+ return ret;
+
+ if (!pwm_gpio->gc.ngpio)
+ return 0;
+
+ return devm_gpiochip_add_data(dev, &pwm_gpio->gc, pwm_gpio);
+}
+
+static int pwm_gpio_remove(struct platform_device *pdev)
+{
+ return 0;
+}
+
+static const struct of_device_id pwm_gpio_of_match[] = {
+ { .compatible = "pwm-gpio" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, pwm_gpio_of_match);
+
+static struct platform_driver pwm_gpio_driver = {
+ .driver = {
+ .name = "pwm-gpio",
+ .of_match_table = of_match_ptr(pwm_gpio_of_match),
+ },
+ .probe = pwm_gpio_probe,
+ .remove = pwm_gpio_remove,
+};
+module_platform_driver(pwm_gpio_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dave Stevenson <dave.stevenson@raspberrypi.com>");
+MODULE_DESCRIPTION("PWM GPIO driver");
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