[Intel-gfx] [RESEND] drm/i915: stop conflating HAS_DISPLAY() and disabled display

[Chris Wilson]

Quoting Jani Nikula (2019-09-16 10:29:01)
> Stop setting ->pipe_mask to zero when display is disabled, allowing us
> to have different code paths for not actually having display hardware,
> and having display hardware disabled. This lets us develop those two
> avenues independently.
> 
> There are no functional changes for when there is no display. However,
> all uses of for_each_pipe() and for_each_pipe_masked() will start
> running for the disabled display case. Put one of the more significant
> ones behind checks for INTEL_DISPLAY_ENABLED(), otherwise the cases
> should not be hit with disabled display, or they seem benign. Fingers
> crossed.
> 
> All in all, this might not be the ideal solution. In fact we may have
> had something along the lines of this in the past, but we ended up
> conflating the two cases. Possibly even by recommendation by yours
> truly; I did not dare dig up that part of the history. But the perfect
> is the enemy of the good, this is a straightforward change, and lets us
> get actual work done in both fronts without interfering with each other.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: José Roberto de Souza <jose.souza at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

It doesn't fall over, which is impressive enough.
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris