[Intel-gfx] [PATCH] drm/i915/dsi: Silence atomic update failure with DSI panel

[Maarten Lankhorst]

Op 05-09-17 om 15:35 schreef Mika Kahola:
> It appears that we cannot trust scanline counters when MIPI/DSI display is
> connected. In CI system this appears as flickering errors that randomly
> appear in test cases. To avoid this flickering, let's just silence atomic
> update failure in case with DSI panel.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102403
> Signed-off-by: Mika Kahola <mika.kahola at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sprite.c | 32 +++++++++++++++++---------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> index b0d6e3e..8511072 100644
> --- a/drivers/gpu/drm/i915/intel_sprite.c
> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> @@ -205,23 +205,25 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
>  	if (intel_vgpu_active(dev_priv))
>  		return;
>  
> -	if (crtc->debug.start_vbl_count &&
> -	    crtc->debug.start_vbl_count != end_vbl_count) {
> -		DRM_ERROR("Atomic update failure on pipe %c (start=%u end=%u) time %lld us, min %d, max %d, scanline start %d, end %d\n",
> -			  pipe_name(pipe), crtc->debug.start_vbl_count,
> -			  end_vbl_count,
> -			  ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
> -			  crtc->debug.min_vbl, crtc->debug.max_vbl,
> -			  crtc->debug.scanline_start, scanline_end);
> -	}
> +	if (!intel_crtc_has_type(new_crtc_state, INTEL_OUTPUT_DSI)) {
> +		if (crtc->debug.start_vbl_count &&
> +		    crtc->debug.start_vbl_count != end_vbl_count) {
> +			DRM_ERROR("Atomic update failure on pipe %c (start=%u end=%u) time %lld us, min %d, max %d, scanline start %d, end %d\n",
> +				  pipe_name(pipe), crtc->debug.start_vbl_count,
> +				  end_vbl_count,
> +				  ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
> +				  crtc->debug.min_vbl, crtc->debug.max_vbl,
> +				  crtc->debug.scanline_start, scanline_end);
> +		}
>  #ifdef CONFIG_DRM_I915_DEBUG_VBLANK_EVADE
> -	else if (ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time) >
> -		 VBLANK_EVASION_TIME_US)
> -		DRM_WARN("Atomic update on pipe (%c) took %lld us, max time under evasion is %u us\n",
> -			 pipe_name(pipe),
> -			 ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
> -			 VBLANK_EVASION_TIME_US);
> +		else if (ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time) >
> +			 VBLANK_EVASION_TIME_US)
> +			DRM_WARN("Atomic update on pipe (%c) took %lld us, max time under evasion is %u us\n",
> +				 pipe_name(pipe),
> +				 ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
> +				 VBLANK_EVASION_TIME_US);
>  #endif
> +	}
>  }
>  
>  static void

I don't think this goes far enough. We should stop claiming accurate vblanks when MIPI/DSI is used.
intel_get_crtc_scanline will currently spin for 100 us to see if we can move from scanline offset = 0,
this means that we add an additional 100 us wait for MIPI/DSI always.

i915_get_crtc_scanoutpos should return false as well.

Does this mean need_vlv_dsi_wa in intel_pipe_update_start is now a noop? Should we perhaps only apply this
for gen9+ MIPI/DSI?

~Maarten