From dbd522842d668d590dd415cc99045a9b1f05aeae Mon Sep 17 00:00:00 2001 From: Dave Stevenson 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 --- 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 @@ -500,6 +500,14 @@ 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 @@ -123,6 +123,7 @@ 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 +#include +#include +#include +#include + +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 "); +MODULE_DESCRIPTION("PWM GPIO driver");