Re: Bug#626013: Please apply upstream fix
reassign 626013 linux-2.6 2.6.38-4
tag 626013 patch upstream fixed-upstream
kthxbye
On Fri, Jul 29, 2011 at 09:25:37 -0500, J-Mag Guthrie wrote:
> frombugzilla-daemon@freedesktop.org toj.mag.guthrie@gmail.com
> dateFri, Jul 29, 2011 at 4:04 AMsubject[Bug 38851] 1360x768 resolution
> slants/wraps-around display in kernels newer than 2.6.32mailed-by
> freedesktop.orgImportant mainly because of your interaction with messages in
> the conversation.
> hide details 4:04 AM (5 hours ago)
>
> https://bugs.freedesktop.org/show_bug.cgi?id=38851
>
> Chris Wilson <chris@chris-wilson.co.uk> changed:
>
> What |Removed |Added
> ------------------------------
> ----------------------------------------------
> Status|NEW |RESOLVED
> Resolution| |FIXED
>
> --- Comment #7 from Chris Wilson <chris@chris-wilson.co.uk> 2011-07-29
> 02:04:34 PDT ---
> I was waiting upon the attachments bugzilla kept stripping. Fortunately Adam
> Jackson found the bug, and in drm-intel-fixes:
>
>
> commit 302983e9059e9ef5de3ca7671918eeb237c5971e
> Author: Adam Jackson <ajax@redhat.com>
> Date: Wed Jul 13 16:32:32 2011 -0400
>
> drm/i915/pch: Fix integer math bugs in panel fitting
>
> 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 <ajax@redhat.com>
> Tested-By: Daniel Manrique <daniel.manrique@canonical.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38851
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: stable@kernel.org
> Signed-off-by: Keith Packard <keithp@keithp.com>
Moving to the kernel, this should make its way to Linus soon.
Cheers,
Julien
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