drivers/pwm/pwm-clk.c

Source file repositories/reference/linux-study-clean/drivers/pwm/pwm-clk.c

File Facts

System
Linux kernel
Corpus path
drivers/pwm/pwm-clk.c
Extension
.c
Size
3622 bytes
Lines
141
Domain
Driver Families
Bucket
drivers/pwm
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct pwm_clk_chip {
	struct clk *clk;
	bool clk_enabled;
};

static inline struct pwm_clk_chip *to_pwm_clk_chip(struct pwm_chip *chip)
{
	return pwmchip_get_drvdata(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_chip *chip;
	struct pwm_clk_chip *pcchip;
	int ret;

	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*pcchip));
	if (IS_ERR(chip))
		return PTR_ERR(chip);
	pcchip = to_pwm_clk_chip(chip);

	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");

	chip->ops = &pwm_clk_ops;

	ret = pwmchip_add(chip);
	if (ret < 0)
		return dev_err_probe(&pdev->dev, ret, "Failed to add pwm chip\n");

	platform_set_drvdata(pdev, chip);
	return 0;
}

static void pwm_clk_remove(struct platform_device *pdev)
{
	struct pwm_chip *chip = platform_get_drvdata(pdev);
	struct pwm_clk_chip *pcchip = to_pwm_clk_chip(chip);

	pwmchip_remove(chip);

	if (pcchip->clk_enabled)
		clk_disable(pcchip->clk);
}

Annotation

Implementation Notes