From e8fa4270536de2e5e8205fb2b90bb26afc471729 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Wed, 12 Aug 2015 11:43:34 +0200 Subject: [PATCH] drm/i915: Only dither on 6bpc panels In commit d328c9d78d64ca11e744fe227096990430a88477 Author: Daniel Vetter Date: Fri Apr 10 16:22:37 2015 +0200 drm/i915: Select starting pipe bpp irrespective or the primary plane we started to select the pipe bpp from sink capabilities and not from the primary framebuffer - that one might change (and we don't want to incur a modeset) and sprites might contain higher bpp content too. We also selected dithering on a 8 bpc screen displaying a 24bpp rgb primary, because pipe_bpp is 24 for such a typical 8 bpc sink, but since the commit mentioned above, base_bpp is always the absolute maximum supported by the hardware, e.g., 36 bpp on my Ironlake chip. Iow. the only way to not get dithering would have been to connect a deep color 12 bpc display, so pipe_bpp == 36 == base_bpp. Hence only enable dithering on 6bpc screens where we difinitely and always want it. Cc: Mario Kleiner Reported-by: Mario Kleiner Signed-off-by: Daniel Vetter Reviewed-and-tested-by: Mario Kleiner Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/intel_display.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 30e0f54ba19d..7a03fdc079b7 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -11826,7 +11826,9 @@ encoder_retry: goto encoder_retry; } - pipe_config->dither = pipe_config->pipe_bpp != base_bpp; + /* Dithering seems to not pass-through bits correctly when it should, so + * only enable it on 6bpc panels. */ + pipe_config->dither = pipe_config->pipe_bpp == 6*3; DRM_DEBUG_KMS("plane bpp: %i, pipe bpp: %i, dithering: %i\n", base_bpp, pipe_config->pipe_bpp, pipe_config->dither); -- 2.20.1