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,
> >>>> * return code check for pm_runtime_get_sync() to take care of failure
> >>>> and exit gracefully.
> >>>> * In remove path runtime PM is disabled before calling snd_card_free().
> >>>> * hda_tegra_disable_clocks() is moved out of CONFIG_PM_SLEEP check.
> >>>> * 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)
> >>>> if (!azx_has_pm_runtime(chip))
> >>>> pm_runtime_forbid(hda->dev);
> >>>>
> >>>> + /* explicit resume if runtime PM is disabled */
> >>>> + if (!pm_runtime_enabled(hda->dev)) {
> >>>> + err = hda_tegra_runtime_resume(hda->dev);
> >>>> + if (err)
> >>>> + goto out_free;
> >>>> + }
> >>>> +
> >>>> 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 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 :)
thanks,
Takashi
