Re: [PATCH] drm/i915: Cache max number of pipes

[Mika Kahola <mika.kahola@intel.com>]

On Thu, 2017-10-12 at 09:55 +0300, Jani Nikula wrote:
> On Thu, 12 Oct 2017, Mika Kahola <mika.kahola@intel.com> wrote:
> > 
> > CI system spotted an error on CFL system when running IGT tests
> > with
> > display disabled. In this case, the 'INTEL_INFO(dev_priv)-
> > >num_pipes'
> > is set to 0. This will cause that we prematurely return from
> > 'get_saved_enc()'.
> > 
> > To fix this issue, the patch introduces a 'max_pipes' variable
> > which caches
> > the maximum number of available pipes.
> This is not the right fix. The audio component init should be skipped
> and thus all component calls blocked when num_pipes == 0. It's just
> that
> the num_pipes = 0 happens way too late when the display is fused off
> or
> disabled via modparam.
> 
> This makes me wonder how many things we actually screw up because
> intel_device_info_runtime_init() happens too
Right. So instead of doing this we shouldn't initialize the audio at
all in case of disabled display? num_pipes variable just gets updated
too late and audio part has already started to initialize itself.
 
>  late.
> 
> > 
> > Reference: https://bugs.freedesktop.org/show_bug.cgi?id=103206
> If this patch fixes the bug, we use Bugzilla: tag. Reference: is for
> other references, e.g. the referenced bug is related to the patch at
> hand somehow, but this does not fix the bug.
> 
> BR,
> Jani.
> 
> 
> > 
> > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h          | 1 +
> >  drivers/gpu/drm/i915/intel_audio.c       | 2 +-
> >  drivers/gpu/drm/i915/intel_device_info.c | 2 ++
> >  3 files changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index 770305b..6229ff8 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -868,6 +868,7 @@ struct intel_device_info {
> >  	u8 num_pipes;
> >  	u8 num_sprites[I915_MAX_PIPES];
> >  	u8 num_scalers[I915_MAX_PIPES];
> > +	u8 max_pipes;
> >  
> >  	unsigned int page_sizes; /* page sizes supported by the HW
> > */
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_audio.c
> > b/drivers/gpu/drm/i915/intel_audio.c
> > index 0ddba16..147bd3d 100644
> > --- a/drivers/gpu/drm/i915/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/intel_audio.c
> > @@ -754,7 +754,7 @@ static struct intel_encoder
> > *get_saved_enc(struct drm_i915_private *dev_priv,
> >  {
> >  	struct intel_encoder *encoder;
> >  
> > -	if (WARN_ON(pipe >= INTEL_INFO(dev_priv)->num_pipes))
> > +	if (WARN_ON(pipe >= INTEL_INFO(dev_priv)->max_pipes))
> >  		return NULL;
> >  
> >  	/* MST */
> > diff --git a/drivers/gpu/drm/i915/intel_device_info.c
> > b/drivers/gpu/drm/i915/intel_device_info.c
> > index 875d428..ba1a807 100644
> > --- a/drivers/gpu/drm/i915/intel_device_info.c
> > +++ b/drivers/gpu/drm/i915/intel_device_info.c
> > @@ -376,6 +376,8 @@ void intel_device_info_runtime_init(struct
> > drm_i915_private *dev_priv)
> >  			info->num_sprites[pipe] = 1;
> >  	}
> >  
> > +	info->max_pipes = info->num_pipes;
> > +
> >  	if (i915_modparams.disable_display) {
> >  		DRM_INFO("Display disabled (module parameter)\n");
> >  		info->num_pipes = 0;
-- 
Mika Kahola - Intel OTC

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