Subject: Re: [PATCH 2/4] pwm: stm32-lp: Add power management support

From: Tomasz Duszynski <[email-masked]>
Date: Tue, 5 Feb 2019 19:30:09 +0100

On Tue, Feb 05, 2019 at 01:40:27PM +0100, Fabrice Gasnier wrote:
> Add suspend/resume PM sleep ops. When going to low power, disable
> active PWM channel. Active PWM channel is resumed, by calling
> pwm_apply_state(). This is inspired by Thierry's comment in [1].
> Don't touch inactive channels, as it may be used by other LPTimer MFD
> child driver.
> [1]https://lkml.org/lkml/2017/12/5/175
>
> Signed-off-by: Fabrice Gasnier <[email-masked]>
> ---
>  drivers/pwm/pwm-stm32-lp.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
> index 0059b24c..0c40d48 100644
> --- a/drivers/pwm/pwm-stm32-lp.c
> +++ b/drivers/pwm/pwm-stm32-lp.c
> @@ -13,6 +13,7 @@
>  #include <linux/mfd/stm32-lptimer.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  #include <linux/pwm.h>
>
> @@ -20,6 +21,8 @@ struct stm32_pwm_lp {
>  	struct pwm_chip chip;
>  	struct clk *clk;
>  	struct regmap *regmap;
> +	struct pwm_state suspend;
> +	bool suspended;
>  };
>
>  static inline struct stm32_pwm_lp *to_stm32_pwm_lp(struct pwm_chip *chip)
> @@ -223,6 +226,40 @@ static int stm32_pwm_lp_remove(struct platform_device *pdev)
>  	return pwmchip_remove(&priv->chip);
>  }
>
> +#ifdef CONFIG_PM_SLEEP

You might consider dropping ifdefs and marking pm functions with
__maybe_unused instead. In case CONFIG_PM_SLEEP=n then these two guys
will be removed and pm ops structure will be empty.

> +static int stm32_pwm_lp_suspend(struct device *dev)
> +{
> +	struct stm32_pwm_lp *priv = dev_get_drvdata(dev);
> +

I guess you first need to get platform_device from dev and eventually
stm32_pwm_lp. Wondering how this works now.

> +	pwm_get_state(&priv->chip.pwms[0], &priv->suspend);
> +	priv->suspended = priv->suspend.enabled;
> +
> +	/* safe to call pwm_disable() for already disabled pwm */
> +	pwm_disable(&priv->chip.pwms[0]);
> +
> +	return pinctrl_pm_select_sleep_state(dev);
> +}
> +
> +static int stm32_pwm_lp_resume(struct device *dev)
> +{
> +	struct stm32_pwm_lp *priv = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = pinctrl_pm_select_default_state(dev);
> +	if (ret)
> +		return ret;
> +
> +	/* Only restore suspended pwm, not to disrupt other MFD child */
> +	if (!priv->suspended)
> +		return 0;

Would it make sense to use suspend.enabled directly?

> +
> +	return pwm_apply_state(&priv->chip.pwms[0], &priv->suspend);
> +}
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(stm32_pwm_lp_pm_ops, stm32_pwm_lp_suspend,
> +			 stm32_pwm_lp_resume);
> +
>  static const struct of_device_id stm32_pwm_lp_of_match[] = {
>  	{ .compatible = "st,stm32-pwm-lp", },
>  	{},
> @@ -235,6 +272,7 @@ static int stm32_pwm_lp_remove(struct platform_device *pdev)
>  	.driver	= {
>  		.name = "stm32-pwm-lp",
>  		.of_match_table = of_match_ptr(stm32_pwm_lp_of_match),
> +		.pm = &stm32_pwm_lp_pm_ops,
>  	},
>  };
>  module_platform_driver(stm32_pwm_lp_driver);
> --
> 1.9.1
>

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