We want to enable dithering on any pipe where the frame buffer has more color resolution than the output device.
The previous code was incorrectly clamping the frame buffer bpc to the display bpc, effectively disabling dithering all of the time as the computed frame buffer bpc would never be larger than the display bpc.
Signed-off-by: Keith Packard keithp@keithp.com Reported-by: Oliver Hartkopp socketcan@hartkopp.net Tested-by: Oliver Hartkopp socketcan@hartkopp.net --- drivers/gpu/drm/i915/intel_display.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 56a8554..9fb4a40 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -4687,13 +4687,13 @@ static bool intel_choose_pipe_bpp_dither(struct drm_crtc *crtc, bpc = 6; /* min is 18bpp */ break; case 24: - bpc = min((unsigned int)8, display_bpc); + bpc = 8; break; case 30: - bpc = min((unsigned int)10, display_bpc); + bpc = 10; break; case 48: - bpc = min((unsigned int)12, display_bpc); + bpc = 12; break; default: DRM_DEBUG("unsupported depth, assuming 24 bits\n"); @@ -4701,10 +4701,12 @@ static bool intel_choose_pipe_bpp_dither(struct drm_crtc *crtc, break; }
+ display_bpc = min(display_bpc, bpc); + DRM_DEBUG_DRIVER("setting pipe bpc to %d (max display bpc %d)\n", bpc, display_bpc);
- *pipe_bpp = bpc * 3; + *pipe_bpp = display_bpc * 3;
return display_bpc != bpc; }