linux/drivers/pwm/pwm-clk.c
Uwe Kleine-König 384461abca pwm: Manage owner assignment implicitly for drivers
Instead of requiring each driver to care for assigning the owner member
of struct pwm_ops, handle that implicitly using a macro. Note that the
owner member has to be moved to struct pwm_chip, as the ops structure
usually lives in read-only memory and so cannot be modified.

The upside is that new low level drivers cannot forget the assignment and
save one line each. The pwm-crc driver didn't assign .owner, that's not
a problem in practice though as the driver cannot be compiled as a
module.

Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com> # Intel LPSS
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com> # pwm-{bcm,brcm}*.c
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com> # sun4i
Acked-by: Andi Shyti <andi.shyti@kernel.org>
Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> # pwm-visconti
Acked-by: Heiko Stuebner <heiko@sntech.de> # pwm-rockchip
Acked-by: Michael Walle <michael@walle.cc> # pwm-sl28cpld
Acked-by: Neil Armstrong <neil.armstrong@linaro.org> # pwm-meson
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230804142707.412137-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2023-10-13 10:07:17 +02:00

138 lines
3.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Clock based PWM controller
*
* Copyright (c) 2021 Nikita Travkin <nikita@trvn.ru>
*
* This is an "adapter" driver that allows PWM consumers to use
* system clocks with duty cycle control as PWM outputs.
*
* Limitations:
* - Due to the fact that exact behavior depends on the underlying
* clock driver, various limitations are possible.
* - Underlying clock may not be able to give 0% or 100% duty cycle
* (constant off or on), exact behavior will depend on the clock.
* - When the PWM is disabled, the clock will be disabled as well,
* line state will depend on the clock.
* - The clk API doesn't expose the necessary calls to implement
* .get_state().
*/
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/pwm.h>
struct pwm_clk_chip {
struct pwm_chip chip;
struct clk *clk;
bool clk_enabled;
};
#define to_pwm_clk_chip(_chip) container_of(_chip, struct pwm_clk_chip, chip)
static int pwm_clk_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct pwm_clk_chip *pcchip = to_pwm_clk_chip(chip);
int ret;
u32 rate;
u64 period = state->period;
u64 duty_cycle = state->duty_cycle;
if (!state->enabled) {
if (pwm->state.enabled) {
clk_disable(pcchip->clk);
pcchip->clk_enabled = false;
}
return 0;
} else if (!pwm->state.enabled) {
ret = clk_enable(pcchip->clk);
if (ret)
return ret;
pcchip->clk_enabled = true;
}
/*
* We have to enable the clk before setting the rate and duty_cycle,
* that however results in a window where the clk is on with a
* (potentially) different setting. Also setting period and duty_cycle
* are two separate calls, so that probably isn't atomic either.
*/
rate = DIV64_U64_ROUND_UP(NSEC_PER_SEC, period);
ret = clk_set_rate(pcchip->clk, rate);
if (ret)
return ret;
if (state->polarity == PWM_POLARITY_INVERSED)
duty_cycle = period - duty_cycle;
return clk_set_duty_cycle(pcchip->clk, duty_cycle, period);
}
static const struct pwm_ops pwm_clk_ops = {
.apply = pwm_clk_apply,
};
static int pwm_clk_probe(struct platform_device *pdev)
{
struct pwm_clk_chip *pcchip;
int ret;
pcchip = devm_kzalloc(&pdev->dev, sizeof(*pcchip), GFP_KERNEL);
if (!pcchip)
return -ENOMEM;
pcchip->clk = devm_clk_get_prepared(&pdev->dev, NULL);
if (IS_ERR(pcchip->clk))
return dev_err_probe(&pdev->dev, PTR_ERR(pcchip->clk),
"Failed to get clock\n");
pcchip->chip.dev = &pdev->dev;
pcchip->chip.ops = &pwm_clk_ops;
pcchip->chip.npwm = 1;
ret = pwmchip_add(&pcchip->chip);
if (ret < 0)
return dev_err_probe(&pdev->dev, ret, "Failed to add pwm chip\n");
platform_set_drvdata(pdev, pcchip);
return 0;
}
static void pwm_clk_remove(struct platform_device *pdev)
{
struct pwm_clk_chip *pcchip = platform_get_drvdata(pdev);
pwmchip_remove(&pcchip->chip);
if (pcchip->clk_enabled)
clk_disable(pcchip->clk);
}
static const struct of_device_id pwm_clk_dt_ids[] = {
{ .compatible = "clk-pwm", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pwm_clk_dt_ids);
static struct platform_driver pwm_clk_driver = {
.driver = {
.name = "pwm-clk",
.of_match_table = pwm_clk_dt_ids,
},
.probe = pwm_clk_probe,
.remove_new = pwm_clk_remove,
};
module_platform_driver(pwm_clk_driver);
MODULE_ALIAS("platform:pwm-clk");
MODULE_AUTHOR("Nikita Travkin <nikita@trvn.ru>");
MODULE_DESCRIPTION("Clock based PWM driver");
MODULE_LICENSE("GPL");