[Intel-gfx] [PATCH]i830_display.c:don't disable vga centering bit.

[Olivier Fourdan]

Hi,

Ma Ling said the following on 02/05/2009 09:48 AM:
 > commit id db9f5915ce812144ffd9d2aa42e8ba
 > which resolved bug #17235, but generate new regression-bug #19715.
 > This patch intends to resolve bug #17235, and avoid regression as well.
 > We have successfully re-tested it for bug #17235 and #19715 respectively.

Actually, I suspect commit db9f5915 has also introduced another
regression when changing resolution with a VGA connected monitor,
which is not addressed by the later commit cdcca959 and is still
present in the latest of the 2.6 branch (2.6.3) apparently.

Without the patch from db9f5915 (and following), changing resolutions
with only VGA connected on a Q45/Q43 chipset works fine and reliably.

However, with that patch applied, the monitor sometimes (roughly half
of the time) goes out of sync after changing the resolution with
xrandr and the display remains black.

to reproduce:

- Connect a monitor to the VGA port
- Select a lower resolution
- If that works, switch back to the original resolution, then select a
lower resolution again.

When that happens, the display may be restored either by switching
back to a text console, or by re-issuing the same xrandr command
again.

Removing the patch fixes that regression but of course reintroduced
the problem reported in #17235.

Cheers,
Olivier.