[Intel-gfx] [PATCH i-g-t] lib: Poll for snd_hda_intel discovery

[Chris Wilson]

Quoting Imre Deak (2018-08-17 10:14:51)
> On Thu, Aug 16, 2018 at 07:01:36PM +0100, Chris Wilson wrote:
> > Loading the sounds modules is asynchronous with the sysfs device
> > hierarchy being instantiated sometime after modprobe returns. As such
> > while we are probing for the sound device, poll a few times to
> > accommodate the async discovery.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Imre Deak <imre.deak at intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> 
> > ---
> >  lib/igt_pm.c | 65 +++++++++++++++++++++++++++++++++-------------------
> >  1 file changed, 41 insertions(+), 24 deletions(-)
> > 
> > diff --git a/lib/igt_pm.c b/lib/igt_pm.c
> > index 6e96db22b..f82707231 100644
> > --- a/lib/igt_pm.c
> > +++ b/lib/igt_pm.c
> > @@ -138,31 +138,17 @@ static void strchomp(char *str)
> >               str[len - 1] = 0;
> >  }
> >  
> > -/**
> > - * igt_pm_enable_audio_runtime_pm:
> > - *
> > - * We know that if we don't enable audio runtime PM, snd_hda_intel will never
> > - * release its power well refcount, and we'll never reach the LPSP state.
> > - * There's no guarantee that it will release the power well if we enable
> > - * runtime PM, but at least we can try.
> > - *
> > - * We don't have any assertions on open since the user may not even have
> > - * snd_hda_intel loaded, which is not a problem.
> > - */
> > -void igt_pm_enable_audio_runtime_pm(void)
> > +static int __igt_pm_enable_audio_runtime_pm(void)
> >  {
> >       char *path = NULL;
> >       struct dirent *de;
> >       DIR *dir;
> > +     int err;
> >       int fd;
> >  
> > -     /* Check if already enabled. */
> > -     if (__igt_pm_audio_runtime_power_save[0])
> > -             return;
> > -
> >       dir = opendir("/sys/class/sound");
> >       if (!dir)
> > -             return;
> > +             return 0;
> >  
> >       /* Find PCI device claimed by snd_hda_intel and tied to i915. */
> >       while ((de = readdir(dir))) {
> > @@ -196,18 +182,17 @@ void igt_pm_enable_audio_runtime_pm(void)
> >                                   de->d_name));
> >  
> >               igt_debug("Audio device path is %s\n", path);
> > -
> >               break;
> >       }
> 
> Could close dir while at it.

Good point.
 
> Reviewed-by: Imre Deak <imre.deak at intel.com>
> 
> This time the catch was that snd_hda_intel's second half of probe is run
> from a scheduled work. (even though the first half returns synchronously
> due to modprobe being synchronous as you found last time)

The results from the CI didn't look too promising, but I'm a bit dubious
as to what exactly was tested and so pushed anyway ;)

What next if it still doesn't discover an audio device?

Hmm, is the /sys/class/sound construction async? I was assuming it was
constructed by the parent snd module long before sna_hda_intel does it
thing.
-Chris