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

[Sameer Pujar]

On 1/30/2019 4:09 PM, Takashi Iwai wrote:
> On Wed, 30 Jan 2019 10:35:35 +0100,
> Jon Hunter wrote:
> > On 28/01/2019 06:06, Sameer Pujar wrote:
> > > On 1/25/2019 7:34 PM, Jon Hunter wrote:
> > > > On 25/01/2019 13:58, Takashi Iwai wrote:
> > > > > On Fri, 25 Jan 2019 14:26:27 +0100,
> > > > > Jon Hunter wrote:
> > > > > > On 25/01/2019 12:40, Takashi Iwai wrote:
> > > > > > > On Fri, 25 Jan 2019 12:36:00 +0100,
> > > > > > > Jon Hunter wrote:
> > > > > > > > On 24/01/2019 19:08, Takashi Iwai wrote:
> > > > > > > > > On Thu, 24 Jan 2019 18:36:43 +0100,
> > > > > > > > > Sameer Pujar wrote:
> > > > > > > > > > If CONFIG_PM is disabled or runtime PM calls are forbidden, the
> > > > > > > > > > clocks
> > > > > > > > > > will not be ON. This could cause issue during probe, where hda init
> > > > > > > > > > setup is done. This patch checks whether runtime PM is enabled
> > > > > > > > > > or not.
> > > > > > > > > > If disabled, clocks are enabled in probe() and disabled in remove()
> > > > > > > > > >
> > > > > > > > > > This patch does following minor changes as cleanup,
> > > > > > > > > >  ÂÂ * return code check for pm_runtime_get_sync() to take care of
> > > > > > > > > > failure
> > > > > > > > > >  ÂÂÂÂ and exit gracefully.
> > > > > > > > > >  ÂÂ * In remove path runtime PM is disabled before calling
> > > > > > > > > > snd_card_free().
> > > > > > > > > >  ÂÂ * hda_tegra_disable_clocks() is moved out of CONFIG_PM_SLEEP
> > > > > > > > > > check.
> > > > > > > > > >  ÂÂ * runtime PM callbacks moved out of CONFIG_PM check
> > > > > > > > > >
> > > > > > > > > > Signed-off-by: Sameer Pujar <spujar@xxxxxxxxxx>
> > > > > > > > > > Reviewed-by: Ravindra Lokhande <rlokhande@xxxxxxxxxx>
> > > > > > > > > > Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> > > > > > > > > (snip)
> > > > > > > > > > @@ -555,6 +553,13 @@ static int hda_tegra_probe(struct
> > > > > > > > > > platform_device *pdev)
> > > > > > > > > >  ÂÂÂÂÂ if (!azx_has_pm_runtime(chip))
> > > > > > > > > >  ÂÂÂÂÂÂÂÂÂ pm_runtime_forbid(hda->dev);
> > > > > > > > > >  Â +ÂÂÂ /* explicit resume if runtime PM is disabled */
> > > > > > > > > > +ÂÂÂ if (!pm_runtime_enabled(hda->dev)) {
> > > > > > > > > > +ÂÂÂÂÂÂÂ err = hda_tegra_runtime_resume(hda->dev);
> > > > > > > > > > +ÂÂÂÂÂÂÂ if (err)
> > > > > > > > > > +ÂÂÂÂÂÂÂÂÂÂÂ goto out_free;
> > > > > > > > > > +ÂÂÂ }
> > > > > > > > > > +
> > > > > > > > > >  ÂÂÂÂÂ schedule_work(&hda->probe_work);
> > > > > > > > > Calling runtime_resume here is really confusing...
> > > > > > > > Why? IMO it is better to have a single handler for resuming the
> > > > > > > > device
> > > > > > > > and so if RPM is not enabled we call the handler directly. This is
> > > > > > > > what
> > > > > > > > we have been advised to do in the past and do in other drivers.
> > > > > > > > See ...
> > > > > > > The point is that we're not "resuming" anything there. It's in the
> > > > > > > early probe stage, and the device state is uninitialized, not really
> > > > > > > suspended. It'd end up with just calling the same helper
> > > > > > > (hda_tegra_enable_clocks()), though.
> > > > > > Yes and you can make the same argument for every driver that calls
> > > > > > pm_runtime_get_sync() during probe to turn on clocks, handle resets,
> > > > > > etc, because at the end of the day the very first call to
> > > > > > pm_runtime_get_sync() invokes the runtime_resume callback, when we have
> > > > > > never been suspended.
> > > > > Although there are some magical pm_runtime_*() in some places, most of
> > > > > such pm_runtime_get_sync() is for the actual runtime PM management (to
> > > > > prevent the runtime suspend), while the code above is for explicitly
> > > > > setting up something for non-PM cases.
> > > > >
> > > > > And if pm_runtime_get_sync() is obviously superfluous, we should
> > > > > remove such calls. Really.
> > > > Yes agree.
> > > >
> > > > > > Yes at the end of the day it is the same and given that we have done
> > > > > > this elsewhere I think it is good to be consistent if/where we can.
> > > > > The code becomes less readable, and that's a good reason against it :)
> > > > I don't its less readable. However, I do think it is less error prone :-)
> > > Do we have a consensus here? Request others to provide opinions to help
> > > close on this.
> > I am not going to block this and ultimately it is Iwai-san call.
> >
> > However, I wonder if it would be appropriate to move the whole ...
> >
> >   if (pm_runtime_enabled())
> >           ret = pm_runtime_get_sync();
> >   else
> >           ret = hda_tegra_runtime_resume();
> >
> > ... into the probe_work function? In other words, we are just resuming
> > when we really need to. Unless I am still misunderstanding Iwai-san
> > comment. Otherwise if Iwai-san is happy with V2 then go with that.
> Only from my personal taste, I find the v2 patch is better.
> It like simpler, after all.  That is, the code in v1 patch
>
> 	probe() {
> 		....
> 		pm_runtime_enable();
> 		....
> 		if (!pm_runtime_enabled())
> 			hda_tegra_runtime_resume();
> 		schedule_work();
> 	}
>
> 	work() {
> 		pm_runtime_get_sync();
> 		....
> 		pm_runtime_put();
> 	}
>
> becomes shorter in v2:
>
> 	probe() {
> 		....
> 		hda_tegra_enable_clocks();
> 		schedule_work();
> 	}
>
> 	work() {
> 		....
> 		pm_runtime_enable();
> 	}
>
>
> However, the point about hda_tegra_remove() you raised in the v2 patch
> is still valid.  (BTW, I guess the discussion followed in that thread
> was somehow misunderstood; your argument was about hda_tegra_remove()
> while Sameer discussed about the probe.)  It can be with
> hda_tegra_disable_clocks() if we want more consistency.
>
> Though, I don't mind too much about that as long as the proper comment
> is given.
We might need entire functionality of hda_tegra_runtime_suspend() 
replicated here,
if hda_tegra_disable_clocks() were to be used. Right now it takes care 
of both the
cases where runtime PM is enabled/disabled. If you all agree, we can 
move the
discussion to v2 patch.

Thanks,
Sameer.
> thanks,
>
> Takashi