[Intel-gfx] [PATCH 1/4] drm/i915/display: Handle fused off display correctly

[Souza, Jose]

On Fri, 2019-10-11 at 15:25 +0300, Ville Syrjälä wrote:
> On Thu, Oct 10, 2019 at 12:32:38PM -0700, José Roberto de Souza
> wrote:
> > If all pipes are fused off it means that display is disabled,
> > similar
> > like we handle for GEN 7 and 8 right above.
> > 
> > On GEN 9 the bit 31 is "Internal Graphics Disable" and on newer
> > GENs

Here should be bit 30 is "Internal Display Disable".
If bit 31 is set I guess not even GT is available but will not handle
this here. 

> > it has another function, probably on GEN 9 when bit 31 is set all
> > the 3 pipes disable bit are set, so we can unify the handling.
> 
> I'm not sure this is really correct. The description says the pipe
> will
> just output a solid color, so the display hardware may be there to
> some
> degree and if we don't want to waste power we may have to power
> manage
> some of it still.
> 
> Not sure how high up we've plugged in the 'pipe_mask==0 -> display
> not
> there' logic. If it's too high up we may leave some power on the
> floor.
> 
> But all that is just speculation on my part. Would probably be good
> to get some clarification to the spec about this stuff.

So would be better set i915_modparams.disable_display = 1, so in future
we can power off.

> 
> > Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_device_info.c | 11 +++++------
> >  1 file changed, 5 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_device_info.c
> > b/drivers/gpu/drm/i915/intel_device_info.c
> > index 85e480bdc673..c01fccfe3cca 100644
> > --- a/drivers/gpu/drm/i915/intel_device_info.c
> > +++ b/drivers/gpu/drm/i915/intel_device_info.c
> > @@ -972,15 +972,14 @@ void intel_device_info_runtime_init(struct
> > drm_i915_private *dev_priv)
> >  			enabled_mask &= ~BIT(PIPE_D);
> >  
> >  		/*
> > -		 * At least one pipe should be enabled and if there are
> > -		 * disabled pipes, they should be the last ones, with
> > no holes
> > -		 * in the mask.
> > +		 * If there are disabled pipes, they should be the last
> > ones,
> > +		 * with no holes in the mask.
> >  		 */
> > -		if (enabled_mask == 0 || !is_power_of_2(enabled_mask +
> > 1))
> > +		if (enabled_mask && !is_power_of_2(enabled_mask + 1))
> >  			DRM_ERROR("invalid pipe fuse configuration:
> > enabled_mask=0x%x\n",
> >  				  enabled_mask);
> > -		else
> > -			info->pipe_mask = enabled_mask;
> > +
> > +		info->pipe_mask = enabled_mask;
> >  	}
> >  
> >  	/* Initialize slice/subslice/EU info */
> > -- 
> > 2.23.0