[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>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 12 +++++++-----
>  drivers/gpu/drm/i915/intel_device_info.c     |  8 ++------
>  2 files changed, 9 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index e75945a53e06..ac24f96582ca 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -16281,11 +16281,13 @@ int intel_modeset_init(struct drm_device *dev)
>                       INTEL_NUM_PIPES(dev_priv),
>                       INTEL_NUM_PIPES(dev_priv) > 1 ? "s" : "");
>  
> -       for_each_pipe(dev_priv, pipe) {
> -               ret = intel_crtc_init(dev_priv, pipe);
> -               if (ret) {
> -                       drm_mode_config_cleanup(dev);
> -                       return ret;
> +       if (HAS_DISPLAY(dev_priv) && INTEL_DISPLAY_ENABLED(dev_priv)) {
> +               for_each_pipe(dev_priv, pipe) {
> +                       ret = intel_crtc_init(dev_priv, pipe);

What direction are you planning to take, avoid enabling anything related
to display? My worry is that in

https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_14418/fi-bsw-kefka/igt@i915_selftest@live_gt_timelines.html

we still see weird events like

<7> [444.313823] [drm:i915_redisable_vga_power_on [i915]] Something enabled VGA plane, disabling it

and I'm not sure how you intend to curtail that. (Or if that's even
possible.)
-Chris