1 // SPDX-License-Identifier: GPL-2.0
3  * Clock based PWM controller
7  * This is an "adapter" driver that allows PWM consumers to use
8  * system clocks with duty cycle control as PWM outputs.
11  * - Due to the fact that exact behavior depends on the underlying
13  * - Underlying clock may not be able to give 0% or 100% duty cycle
15  * - When the PWM is disabled, the clock will be disabled as well,
17  * - The clk API doesn't expose the necessary calls to implement
27 #include <linux/clk.h>
28 #include <linux/pwm.h>
31 	struct clk *clk;  member
40 static int pwm_clk_apply(struct pwm_chip *chip, struct pwm_device *pwm,  in pwm_clk_apply()  argument
46 	u64 period = state->period;  in pwm_clk_apply()
47 	u64 duty_cycle = state->duty_cycle;  in pwm_clk_apply()
49 	if (!state->enabled) {  in pwm_clk_apply()
50 		if (pwm->state.enabled) {  in pwm_clk_apply()
51 			clk_disable(pcchip->clk);  in pwm_clk_apply()
52 			pcchip->clk_enabled = false;  in pwm_clk_apply()
55 	} else if (!pwm->state.enabled) {  in pwm_clk_apply()
56 		ret = clk_enable(pcchip->clk);  in pwm_clk_apply()
59 		pcchip->clk_enabled = true;  in pwm_clk_apply()
63 	 * We have to enable the clk before setting the rate and duty_cycle,  in pwm_clk_apply()
64 	 * that however results in a window where the clk is on with a  in pwm_clk_apply()
70 	ret = clk_set_rate(pcchip->clk, rate);  in pwm_clk_apply()
74 	if (state->polarity == PWM_POLARITY_INVERSED)  in pwm_clk_apply()
75 		duty_cycle = period - duty_cycle;  in pwm_clk_apply()
77 	return clk_set_duty_cycle(pcchip->clk, duty_cycle, period);  in pwm_clk_apply()
90 	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*pcchip));  in pwm_clk_probe()
95 	pcchip->clk = devm_clk_get_prepared(&pdev->dev, NULL);  in pwm_clk_probe()
96 	if (IS_ERR(pcchip->clk))  in pwm_clk_probe()
97 		return dev_err_probe(&pdev->dev, PTR_ERR(pcchip->clk),  in pwm_clk_probe()
100 	chip->ops = &pwm_clk_ops;  in pwm_clk_probe()
104 		return dev_err_probe(&pdev->dev, ret, "Failed to add pwm chip\n");  in pwm_clk_probe()
117 	if (pcchip->clk_enabled)  in pwm_clk_remove()
118 		clk_disable(pcchip->clk);  in pwm_clk_remove()
122 	{ .compatible = "clk-pwm", },
129 		.name = "pwm-clk",
137 MODULE_ALIAS("platform:pwm-clk");
139 MODULE_DESCRIPTION("Clock based PWM driver");