pwm: renesas-tpu: Add suspend/resume function

This patch adds suspend/resume function support for Renesas the 16-Bit Timer
Pulse Unit (TPU) driver. This has been tested on the Salvator-XS board 
with R-Car M3-N and H3 at renesas-drivers-2019-05-21-v5.2-rc1 tag.
I expect this to work on other SoCs.

Test procedure:
  - Enable TPU and pin control in DTS.
  - Make sure switches { SW29-[1-2] are switched off or 
    SW31-[1-4] are switched off(only for Salvator-xs) }.
  - Exercise userspace PWM control for pwm[2,3] 
    of /sys/class/pwm/pwmchip1/ .
  - Inspect PWM signals on the input side of { CN29-[58,60] 
    or SW31-[1,2] (only for Salvator-xs) }
    before and after suspend/resume using an oscilloscope. 

Signed-off-by: Cao Van Dong <cv-dong@jinso.co.jp>
Tested-by: Cao Van Dong <cv-dong@jinso.co.jp>
---
 drivers/pwm/pwm-renesas-tpu.c | 49 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

On 2019/05/22 17:06, Cao Van Dong wrote:
> This patch adds suspend/resume function support for Renesas the 16-Bit Timer
> Pulse Unit (TPU) driver. This has been tested on the Salvator-XS board
> with R-Car M3-N and H3 at renesas-drivers-2019-05-21-v5.2-rc1 tag.
> I expect this to work on other SoCs.
>
> Test procedure:
>    - Enable TPU and pin control in DTS.
>    - Make sure switches { SW29-[1-2] are switched off or
>      SW31-[1-4] are switched off(only for Salvator-xs) }.
>    - Exercise userspace PWM control for pwm[2,3]
>      of /sys/class/pwm/pwmchip1/ .
>    - Inspect PWM signals on the input side of { CN29-[58,60]
>      or SW31-[1,2] (only for Salvator-xs) }
>      before and after suspend/resume using an oscilloscope.
>
> Signed-off-by: Cao Van Dong <cv-dong@jinso.co.jp>
> Tested-by: Cao Van Dong <cv-dong@jinso.co.jp>
> ---
>   drivers/pwm/pwm-renesas-tpu.c | 49 +++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 49 insertions(+)
>
> diff --git a/drivers/pwm/pwm-renesas-tpu.c b/drivers/pwm/pwm-renesas-tpu.c
> index 4a855a2..97b026e 100644
> --- a/drivers/pwm/pwm-renesas-tpu.c
> +++ b/drivers/pwm/pwm-renesas-tpu.c
> @@ -366,6 +366,54 @@ static void tpu_pwm_disable(struct pwm_chip *chip, struct pwm_device *_pwm)
>   	tpu_pwm_timer_stop(pwm);
>   }
>   
> +#ifdef CONFIG_PM_SLEEP
> +static struct pwm_device *tpu_pwm_dev_to_pwm_dev(struct device *dev)
> +{
> +	struct tpu_device *tpu = dev_get_drvdata(dev);
> +	struct pwm_chip *chip = &tpu->chip;
> +
> +	if((pwm_get_chip_data(&chip->pwms[0])) != NULL)
> +		return &chip->pwms[0];
> +	if((pwm_get_chip_data(&chip->pwms[1])) != NULL)
> +		return &chip->pwms[1];
> +	if((pwm_get_chip_data(&chip->pwms[2])) != NULL)
> +		return &chip->pwms[2];
> +	if((pwm_get_chip_data(&chip->pwms[3])) != NULL)
> +		return &chip->pwms[3];

Sorry everyone,

The current handling code only cover the case of using a timer.
In case of using multiple timers at a time, it will not be able
to restart all of them. Therefore, I will repair it to cover all
and resubmit in version v2.

Thank you,
Dong

> +	return NULL;
> +}
> +
> +static int tpu_pwm_suspend(struct device *dev)
> +{
> +	struct pwm_device *pwm = tpu_pwm_dev_to_pwm_dev(dev);
> +
> +	if (!test_bit(PWMF_REQUESTED, &pwm->flags))
> +		return 0;
> +
> +	pm_runtime_put(dev);
> +
> +	return 0;
> +}
> +
> +static int tpu_pwm_resume(struct device *dev)
> +{
> +	struct pwm_device *pwm = tpu_pwm_dev_to_pwm_dev(dev);
> +
> +	if ((!test_bit(PWMF_REQUESTED, &pwm->flags)) || pwm == NULL)
> +		return 0;
> +
> +	pm_runtime_get_sync(dev);
> +
> +	/* Restart timer */
> +	tpu_pwm_disable(pwm->chip,pwm);
> +	tpu_pwm_enable(pwm->chip,pwm);
> +
> +	return 0;
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +static SIMPLE_DEV_PM_OPS(tpu_pwm_pm_ops, tpu_pwm_suspend, tpu_pwm_resume);
> +
>   static const struct pwm_ops tpu_pwm_ops = {
>   	.request = tpu_pwm_request,
>   	.free = tpu_pwm_free,
> @@ -459,6 +507,7 @@ static struct platform_driver tpu_driver = {
>   	.remove		= tpu_remove,
>   	.driver		= {
>   		.name	= "renesas-tpu-pwm",
> +		.pm		= &tpu_pwm_pm_ops,
>   		.of_match_table = of_match_ptr(tpu_of_table),
>   	}
>   };