From 3ecc15991c860a72371f7bb49854967324109b15 Mon Sep 17 00:00:00 2001 From: Adam Jackson Date: Mon, 1 Aug 2011 15:19:55 +0100 Subject: [PATCH] UBUNTU: SAUCE: drm/i915/pch: Fix integer math bugs in panel fitting MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Currently sitting in the drm-intel/drm-intel-fixes branch Consider a 1600x900 panel, upscaling a 1360x768 mode, full-aspect. The old math would give you: scaled_width = 1600 * 768; /* 1228800 */ scaled_height = 1360 * 900; /* 1224000 */ if (scaled_width > scaled_height) { /* pillarbox, and true */ width = 1224000 / 768; /* int(1593.75) = 1593 */ x = (1600 - 1593 + 1) / 2; /* 4 */ y = 0; height = 768; } /* ... */ This is broken. The total width of scanout would then be 1593 + 4 + 4, or 1601, which is wider than the panel itself. The hardware very dutifully implements this, and you end up with a black 45° diagonal from the top-left corner to the bottom edge of the screen. It's a cool effect and all, but not what you wanted. Similar things happen for the letterbox case. The problem is that you have an integer number of pixels, which means it's usually impossible to upscale equally on both axes. 1360/768 is 1.7708, 1600/900 is 1.7777. Since we're constrained on the one axis, the other one wants to come out as an even number of pixels (the panel is almost certainly even on both axes, and the x/y offsets will be applied on both sides). In the math above, if 'width' comes out even, rounding down is correct; if it's odd, you'd rather round up. So just increment width/height in those cases. Tested on a Lenovo T500 (Ironlake). Signed-off-by: Adam Jackson Tested-By: Daniel Manrique Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38851 Reviewed-by: Chris Wilson Cc: stable@kernel.org Signed-off-by: Keith Packard BugLink: http://bugs.launchpad.net/bugs/753994 Signed-off-by: Andy Whitcroft Signed-off-by: Tim Gardner Acked-by: Leann Ogasawara --- drivers/gpu/drm/i915/intel_panel.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index f8f86e5..db8733e 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -83,11 +83,15 @@ intel_pch_panel_fitting(struct drm_device *dev, u32 scaled_height = mode->hdisplay * adjusted_mode->vdisplay; if (scaled_width > scaled_height) { /* pillar */ width = scaled_height / mode->vdisplay; + if (width & 1) + width++; x = (adjusted_mode->hdisplay - width + 1) / 2; y = 0; height = adjusted_mode->vdisplay; } else if (scaled_width < scaled_height) { /* letter */ height = scaled_width / mode->hdisplay; + if (height & 1) + height++; y = (adjusted_mode->vdisplay - height + 1) / 2; x = 0; width = adjusted_mode->hdisplay; -- 1.7.10.4