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SubjectRe: [PATCH 2/4] pwm: stm32-lp: Add power management support
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On 2/5/19 7:30 PM, Tomasz Duszynski wrote:
> 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 <fabrice.gasnier@st.com>
>> ---
>> 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.

Hi Tomasz,

Thanks for this suggestion. I can do this change. I'll wait for more
feedback from Uwe and Thierry before sending a v2 with that.

>
>> +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.

This should be safe for now. This works because the probe routine calls:
platform_set_drvdata(pdev, priv);

And the underlying call is dev_set_drvdata()
static inline void platform_set_drvdata(struct platform_device *pdev,
void *data)
{
dev_set_drvdata(&pdev->dev, data);
}

>
>> + 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?

I propose to keep priv->suspended. Using 'suspend.enabled' directly
would simply not work as the pwm_disable() call in
stm32_pwm_lp_suspend() routine marks the 'suspend' state.enabled = false.
That's why it's saved in the suspend routine, to be restored upon resume.

Thanks for reviewing,
Best regards,
Fabrice

>
>> +
>> + 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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