linux-kernel - [PATCH] drm/i915: Enable dither whenever display bpc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Mon,  5 Sep 2011 12:00:15 -0700
From:	Keith Packard <keithp@...thp.com>
To:	Dave Airlie <airlied@...hat.com>
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	intel-gfx@...ts.freedesktop.org, Keith Packard <keithp@...thp.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oliver Hartkopp <socketcan@...tkopp.net>
Subject: [PATCH] drm/i915: Enable dither whenever display bpc < frame buffer bpc

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@...thp.com>
Reported-by: Oliver Hartkopp <socketcan@...tkopp.net>
Tested-by: Oliver Hartkopp <socketcan@...tkopp.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;
 }
-- 
1.7.5.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/