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Signed-off-by: Nicola Di Lieto Co-developed-by: Stefan Wahren Signed-off-by: Stefan Wahren Reviewed-by: Linus Walleij Reviewed-by: Krzysztof Kozlowski Reviewed-by: Dhruva Gole Signed-off-by: Linus Walleij Reviewed-by: Linus Walleij for the above patch! --- .../devicetree/bindings/pwm/pwm-gpio.yaml | 42 ++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/Documentation/devicetree/bindings/pwm/pwm-gpio.yaml b/Documentation/devicetree/bindings/pwm/pwm-gpio.yaml new file mode 100644 index 000000000000..1a1281e0fbd7 --- /dev/null +++ b/Documentation/devicetree/bindings/pwm/pwm-gpio.yaml @@ -0,0 +1,42 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/pwm/pwm-gpio.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Generic software PWM for modulating GPIOs + +maintainers: + - Stefan Wahren + +allOf: + - $ref: pwm.yaml# + +properties: + compatible: + const: pwm-gpio + + "#pwm-cells": + const: 3 + + gpios: + description: + GPIO to be modulated + maxItems: 1 + +required: + - compatible + - "#pwm-cells" + - gpios + +additionalProperties: false + +examples: + - | + #include + + pwm { + #pwm-cells = <3>; 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Sun, 02 Jun 2024 13:33:20 -0700 (PDT) Received: from [192.168.1.140] ([85.235.12.238]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-52b98845508sm245859e87.288.2024.06.02.13.33.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Jun 2024 13:33:19 -0700 (PDT) From: Linus Walleij Date: Sun, 02 Jun 2024 22:33:09 +0200 Subject: [PATCH v6 2/2] pwm: Add GPIO PWM driver Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240602-pwm-gpio-v6-2-e8f6ec9cc783@linaro.org> References: <20240602-pwm-gpio-v6-0-e8f6ec9cc783@linaro.org> In-Reply-To: <20240602-pwm-gpio-v6-0-e8f6ec9cc783@linaro.org> To: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , Rob Herring , Krzysztof Kozlowski , Conor Dooley , andy.shevchenko@gmail.com, Philip Howard , Sean Young , Chris Morgan , Stefan Wahren , linux-gpio@vger.kernel.org, linux-pwm@vger.kernel.org, devicetree@vger.kernel.org Cc: Linus Walleij , Vincent Whitchurch X-Mailer: b4 0.13.0 From: Vincent Whitchurch Add a software PWM which toggles a GPIO from a high-resolution timer. This will naturally not be as accurate or as efficient as a hardware PWM, but it is useful in some cases. I have for example used it for evaluating LED brightness handling (via leds-pwm) on a board where the LED was just hooked up to a GPIO, and for a simple verification of the timer frequency on another platform. Since high-resolution timers are used, sleeping GPIO chips are not supported and are rejected in the probe function. Signed-off-by: Vincent Whitchurch Co-developed-by: Stefan Wahren Signed-off-by: Stefan Wahren Co-developed-by: Linus Walleij Signed-off-by: Linus Walleij Reviewed-by: Andy Shevchenko --- Documentation/driver-api/gpio/drivers-on-gpio.rst | 7 +- drivers/pwm/Kconfig | 11 + drivers/pwm/Makefile | 1 + drivers/pwm/pwm-gpio.c | 243 ++++++++++++++++++++++ 4 files changed, 261 insertions(+), 1 deletion(-) diff --git a/Documentation/driver-api/gpio/drivers-on-gpio.rst b/Documentation/driver-api/gpio/drivers-on-gpio.rst index af632d764ac6..95572d2a94ce 100644 --- a/Documentation/driver-api/gpio/drivers-on-gpio.rst +++ b/Documentation/driver-api/gpio/drivers-on-gpio.rst @@ -27,7 +27,12 @@ hardware descriptions such as device tree or ACPI: to the lines for a more permanent solution of this type. - gpio-beeper: drivers/input/misc/gpio-beeper.c is used to provide a beep from - an external speaker connected to a GPIO line. + an external speaker connected to a GPIO line. (If the beep is controlled by + off/on, for an actual PWM waveform, see pwm-gpio below.) + +- pwm-gpio: drivers/pwm/pwm-gpio.c is used to toggle a GPIO with a high + resolution timer producing a PWM waveform on the GPIO line, as well as + Linux high resolution timers can do. - extcon-gpio: drivers/extcon/extcon-gpio.c is used when you need to read an external connector status, such as a headset line for an audio driver or an diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 1dd7921194f5..68ba28d52c4c 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -223,6 +223,17 @@ config PWM_FSL_FTM To compile this driver as a module, choose M here: the module will be called pwm-fsl-ftm. +config PWM_GPIO + tristate "GPIO PWM support" + depends on GPIOLIB + depends on HIGH_RES_TIMERS + help + Generic PWM framework driver for software PWM toggling a GPIO pin + from kernel high-resolution timers. + + To compile this driver as a module, choose M here: the module + will be called pwm-gpio. + config PWM_HIBVT tristate "HiSilicon BVT PWM support" depends on ARCH_HISI || COMPILE_TEST diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 90913519f11a..65d62cc41a8f 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -18,6 +18,7 @@ obj-$(CONFIG_PWM_DWC_CORE) += pwm-dwc-core.o obj-$(CONFIG_PWM_DWC) += pwm-dwc.o obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o +obj-$(CONFIG_PWM_GPIO) += pwm-gpio.o obj-$(CONFIG_PWM_HIBVT) += pwm-hibvt.o obj-$(CONFIG_PWM_IMG) += pwm-img.o obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o diff --git a/drivers/pwm/pwm-gpio.c b/drivers/pwm/pwm-gpio.c new file mode 100644 index 000000000000..32ae9bba87c3 --- /dev/null +++ b/drivers/pwm/pwm-gpio.c @@ -0,0 +1,243 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic software PWM for modulating GPIOs + * + * Copyright (C) 2020 Axis Communications AB + * Copyright (C) 2020 Nicola Di Lieto + * Copyright (C) 2024 Stefan Wahren + * Copyright (C) 2024 Linus Walleij + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +struct pwm_gpio { + struct hrtimer gpio_timer; + struct gpio_desc *gpio; + struct pwm_state state; + struct pwm_state next_state; + + /* Protect internal state between pwm_ops and hrtimer */ + spinlock_t lock; + + bool changing; + bool running; + bool level; +}; + +static void pwm_gpio_round(struct pwm_state *dest, const struct pwm_state *src) +{ + u64 dividend; + u32 remainder; + + *dest = *src; + + /* Round down to hrtimer resolution */ + dividend = dest->period; + remainder = do_div(dividend, hrtimer_resolution); + dest->period -= remainder; + + dividend = dest->duty_cycle; + remainder = do_div(dividend, hrtimer_resolution); + dest->duty_cycle -= remainder; +} + +static u64 pwm_gpio_toggle(struct pwm_gpio *gpwm, bool level) +{ + const struct pwm_state *state = &gpwm->state; + bool invert = state->polarity == PWM_POLARITY_INVERSED; + + gpwm->level = level; + gpiod_set_value(gpwm->gpio, gpwm->level ^ invert); + + if (!state->duty_cycle || state->duty_cycle == state->period) { + gpwm->running = false; + return 0; + } + + gpwm->running = true; + return level ? state->duty_cycle : state->period - state->duty_cycle; +} + +static enum hrtimer_restart pwm_gpio_timer(struct hrtimer *gpio_timer) +{ + struct pwm_gpio *gpwm = container_of(gpio_timer, struct pwm_gpio, + gpio_timer); + u64 next_toggle; + bool new_level; + + guard(spinlock_irqsave)(&gpwm->lock); + + /* Apply new state at end of current period */ + if (!gpwm->level && gpwm->changing) { + gpwm->changing = false; + gpwm->state = gpwm->next_state; + new_level = !!gpwm->state.duty_cycle; + } else { + new_level = !gpwm->level; + } + + next_toggle = pwm_gpio_toggle(gpwm, new_level); + if (next_toggle) + hrtimer_forward(gpio_timer, hrtimer_get_expires(gpio_timer), + ns_to_ktime(next_toggle)); + + return next_toggle ? HRTIMER_RESTART : HRTIMER_NORESTART; +} + +static int pwm_gpio_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip); + bool invert = state->polarity == PWM_POLARITY_INVERSED; + + if (state->duty_cycle && state->duty_cycle < hrtimer_resolution) + return -EINVAL; + + if (state->duty_cycle != state->period && + (state->period - state->duty_cycle < hrtimer_resolution)) + return -EINVAL; + + if (!state->enabled) { + hrtimer_cancel(&gpwm->gpio_timer); + } else if (!gpwm->running) { + int ret; + + /* + * This just enables the output, but pwm_gpio_toggle() + * really starts the duty cycle. + */ + ret = gpiod_direction_output(gpwm->gpio, invert); + if (ret) + return ret; + } + + guard(spinlock_irqsave)(&gpwm->lock); + + if (!state->enabled) { + pwm_gpio_round(&gpwm->state, state); + gpwm->running = false; + gpwm->changing = false; + + gpiod_set_value(gpwm->gpio, invert); + } else if (gpwm->running) { + pwm_gpio_round(&gpwm->next_state, state); + gpwm->changing = true; + } else { + unsigned long next_toggle; + + pwm_gpio_round(&gpwm->state, state); + gpwm->changing = false; + + next_toggle = pwm_gpio_toggle(gpwm, !!state->duty_cycle); + if (next_toggle) + hrtimer_start(&gpwm->gpio_timer, next_toggle, + HRTIMER_MODE_REL); + } + + return 0; +} + +static int pwm_gpio_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct pwm_gpio *gpwm = pwmchip_get_drvdata(chip); + + guard(spinlock_irqsave)(&gpwm->lock); + + if (gpwm->changing) + *state = gpwm->next_state; + else + *state = gpwm->state; + + return 0; +} + +static const struct pwm_ops pwm_gpio_ops = { + .apply = pwm_gpio_apply, + .get_state = pwm_gpio_get_state, +}; + +static void pwm_gpio_disable_hrtimer(void *data) +{ + struct pwm_gpio *gpwm = data; + + hrtimer_cancel(&gpwm->gpio_timer); +} + +static int pwm_gpio_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct pwm_chip *chip; + struct pwm_gpio *gpwm; + int ret; + + chip = devm_pwmchip_alloc(dev, 1, sizeof(*gpwm)); + if (IS_ERR(chip)) + return PTR_ERR(chip); + + gpwm = pwmchip_get_drvdata(chip); + + spin_lock_init(&gpwm->lock); + + gpwm->gpio = devm_gpiod_get(dev, NULL, GPIOD_ASIS); + if (IS_ERR(gpwm->gpio)) + return dev_err_probe(dev, PTR_ERR(gpwm->gpio), + "%pfw: could not get gpio\n", + dev_fwnode(dev)); + + if (gpiod_cansleep(gpwm->gpio)) + return dev_err_probe(dev, -EINVAL, + "%pfw: sleeping GPIO not supported\n", + dev_fwnode(dev)); + + chip->ops = &pwm_gpio_ops; + chip->atomic = true; + + hrtimer_init(&gpwm->gpio_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + ret = devm_add_action_or_reset(dev, pwm_gpio_disable_hrtimer, gpwm); + if (ret) + return ret; + + gpwm->gpio_timer.function = pwm_gpio_timer; + + ret = pwmchip_add(chip); + if (ret < 0) + return dev_err_probe(dev, ret, "could not add pwmchip\n"); + + platform_set_drvdata(pdev, gpwm); + + return 0; +} + +static const struct of_device_id pwm_gpio_dt_ids[] = { + { .compatible = "pwm-gpio" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pwm_gpio_dt_ids); + +static struct platform_driver pwm_gpio_driver = { + .driver = { + .name = "pwm-gpio", + .of_match_table = pwm_gpio_dt_ids, + }, + .probe = pwm_gpio_probe, +}; +module_platform_driver(pwm_gpio_driver); + +MODULE_DESCRIPTION("PWM GPIO driver"); +MODULE_AUTHOR("Vincent Whitchurch"); +MODULE_LICENSE("GPL");