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SubjectRe: [PATCH v2 3/3] pwm: stm32: add power management support
On Fri, Oct 04, 2019 at 02:53:53PM +0200, Fabrice Gasnier wrote:
> Add suspend/resume PM sleep ops. When going to low power, enforce the PWM
> channel isn't active. Let the PWM consumers disable it during their own
> suspend sequence, see [1]. So, perform a check here, and handle the
> pinctrl states. Also restore the break inputs upon resume, as registers
> content may be lost when going to low power mode.
>
> [1] https://lkml.org/lkml/2019/2/5/770
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> ---
> Changes in v2:
> Follow Uwe suggestions/remarks:
> - Add a precursor patch to ease reviewing
> - Use registers read instead of pwm_get_state
> - Add a comment to mention registers content may be lost in low power mode
> ---
> drivers/pwm/pwm-stm32.c | 38 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 38 insertions(+)

Applied, thanks. I made two minor changes, though, see below.

>
> diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
> index cf8658c..546b661 100644
> --- a/drivers/pwm/pwm-stm32.c
> +++ b/drivers/pwm/pwm-stm32.c
> @@ -12,6 +12,7 @@
> #include <linux/mfd/stm32-timers.h>
> #include <linux/module.h>
> #include <linux/of.h>
> +#include <linux/pinctrl/consumer.h>
> #include <linux/platform_device.h>
> #include <linux/pwm.h>
>
> @@ -655,6 +656,42 @@ static int stm32_pwm_remove(struct platform_device *pdev)
> return 0;
> }
>
> +static int __maybe_unused stm32_pwm_suspend(struct device *dev)
> +{
> + struct stm32_pwm *priv = dev_get_drvdata(dev);
> + unsigned int ch;

I renamed this to just "i", which is more idiomatic for loop variables.
The function is small enough not to need to differentiate between loop
variables.

> + u32 ccer, mask;
> +
> + /* Look for active channels */
> + ccer = active_channels(priv);
> +
> + for (ch = 0; ch < priv->chip.npwm; ch++) {
> + mask = TIM_CCER_CC1E << (ch * 4);
> + if (ccer & mask) {
> + dev_err(dev, "The consumer didn't stop us (%s)\n",
> + priv->chip.pwms[ch].label);

Changed this to:

"PWM %u still in use by consumer %s\n", i, priv->chip.pwms[i].label

I think that might help clarify which PWM is still enabled in case the
consumers don't set a label.

Thierry

> + return -EBUSY;
> + }
> + }
> +
> + return pinctrl_pm_select_sleep_state(dev);
> +}
> +
> +static int __maybe_unused stm32_pwm_resume(struct device *dev)
> +{
> + struct stm32_pwm *priv = dev_get_drvdata(dev);
> + int ret;
> +
> + ret = pinctrl_pm_select_default_state(dev);
> + if (ret)
> + return ret;
> +
> + /* restore breakinput registers that may have been lost in low power */
> + return stm32_pwm_apply_breakinputs(priv);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(stm32_pwm_pm_ops, stm32_pwm_suspend, stm32_pwm_resume);
> +
> static const struct of_device_id stm32_pwm_of_match[] = {
> { .compatible = "st,stm32-pwm", },
> { /* end node */ },
> @@ -667,6 +704,7 @@ static struct platform_driver stm32_pwm_driver = {
> .driver = {
> .name = "stm32-pwm",
> .of_match_table = stm32_pwm_of_match,
> + .pm = &stm32_pwm_pm_ops,
> },
> };
> module_platform_driver(stm32_pwm_driver);
> --
> 2.7.4
>
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