Re: [PATCH v2] ALSA: hda/tegra: enable clock during probe

[Jon Hunter <jonathanh@nvidia.com>]

On 04/02/2019 08:16, Sameer Pujar wrote:

...

> Objective is to have things working with or without CONFIG_PM enabled.
> From previous comments and discussions it appears that there is mixed
> response
> for calling hda_tegra_runtime_resume() or runtime PM APIs in probe()
> call. Need
> to have consensus regarding the best practice to be followed, which
> would eventually
> can be used in other drivers too.
> 
> Rafael is suggesting to use CONFIG_PM check to do manual setup or
> runtime PM setup in probe,
> which would bring back the earlier above mentioned concern.
> 
> if (IS_ENABLED(CONFIG_PM)) {
> do setup based on pm-runtime
> } else {
>     do manual setup
> }
> Both if/else might end up doing the same here.
> Do we really need CONFIG_PM check here?
> 
> Instead does below proposal appear fine?
> 
> probe() {
>     hda_tegra_enable_clock();
> }
> 
> probe_work() {
>     /* hda setup */
>     . . .
>     pm_runtime_set_active(); /* initial state as active */
>     pm_runtime_enable();
>     return;
> }

I believe that this still does not work, because if there is a
power-domain that needs to be turned on, this does not guarantee this.
So I think that you need to call pm_runtime_get ...

 probe() {
 	if (!IS_ENABLED(CONFIG_PM))
 		hda_tegra_enable_clock();
 }


 probe_work() {
    	/* hda setup */
    	. . .
	pm_runtime_enable();
	pm_runtime_get_sync();
	return;
 }

The alternative here could just be ...

 probe() {
	pm_runtime_enable();
 	if (!pm_runtime_enabled())
 		ret = hda_tegra_enable_clock();
	else
		ret = pm_runtime_get_sync();

	if (ret < 0) {
		...
	}
 }

Very similar to what I was saying to begin with but not call the
pm_runtime_resume handler directly. Which I believe was Iwai-san's dislike.

Cheers
Jon

-- 
nvpublic