[Intel-gfx] [PATCH] drm/i915: Return early when pipes are not available

[Mika Kahola]

On Fri, 2017-11-10 at 15:22 +0200, Jani Nikula wrote:
> On Fri, 10 Nov 2017, Mika Kahola <mika.kahola at intel.com> wrote:
> > 
> > On Thu, 2017-11-09 at 15:15 +0200, Ville Syrjälä wrote:
> > > 
> > > On Thu, Nov 09, 2017 at 01:11:05PM +0200, Mika Kahola wrote:
> > > > 
> > > > 
> > > > On Thu, 2017-11-09 at 11:01 +0000, Chris Wilson wrote:
> > > > > 
> > > > > 
> > > > > Quoting Mika Kahola (2017-11-09 10:49:52)
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > At least in Coffee Lake it happens that we start
> > > > > > initiliazing
> > > > > > audio
> > > > > > when
> > > > > > no display is connected. This was discovered by CI when
> > > > > > running
> > > > > > IGT
> > > > > > test
> > > > > > case
> > > > > > 
> > > > > > drv_module_reload --r basic-no-display
> > > > > > 
> > > > > > The issue here is that the
> > > > > > 'intel_device_info_runtime_init()'
> > > > > > sets
> > > > > > num_pipes to 0 but before this happens the audio part has
> > > > > > already
> > > > > > started
> > > > > > to initialize itself. Later on the num_pipes is updated to
> > > > > > 0 in
> > > > > > intel_device_info_runtime_init() and we hit that when audio
> > > > > > part is
> > > > > > digging
> > > > > > out ELD. This causes a warning in dmesg. To fix this issue,
> > > > > > let's
> > > > > > check the
> > > > > > number of available pipes when trying to read out ELD.
> > > > > dev_info_runtime_init() is too late. It depends on mmio being
> > > > > enabled
> > > > > to
> > > > > probe the HW and nothing else; so move it to
> > > > > i915_driver_init_mmio()?
> > > > Ok. I could try that. I was also thinking that is there a way
> > > > to
> > > > postpone audio initialization?
> > > We probably shouldn't be registering the audio thing until we've
> > > actually set up the outputs.
> > I tried couple of versions. One with Chris's idea to move
> > intel_device_info_runtime_init() to i915_driver_init_mmio() didn't
> > turn
> > out to be a success. 
> > 
> > https://patchwork.freedesktop.org/series/33514/
> > 
> > I also tried to set num_pipes to 0 in case of display disable
> > already
> > in i915_driver_init_early(). That approach didn't turn out to be a
> > success either.
> > 
> > https://patchwork.freedesktop.org/series/33522/
> > 
> > I'll give it a go for a patch that doesn't register audio in case
> > of
> > disabled display.
> That seems like the way to go. Display disable on the command line
> should be no different from num_pipes == 0.
Yeah, let's skip this patch for this. I tested another patch that
doesn't register the audio in case of disabled display. At least the
trybot run for this patch was clean.

https://patchwork.freedesktop.org/series/33601/


> 
> BR,
> Jani.
> 
-- 
Mika Kahola - Intel OTC