linux-stable/drivers/gpu
Chris Wilson 0de009c900 drm/i915/crt: Remove 0xa0 probe for VGA
This is a moral revert of 6ec3d0c0e9.

Following the fix to reset the GMBUS controller after a NAK, we finally
utilize the 0xa0 probe for a CRT connection. And discover that the code
is broken. Shock.

There are a number of issues, but following a key insight from Dave
Airlie, that 0xA0 is an invalid address on a 7-bit bus (though not if we
were to enable 10-bit addressing), and would look like the EDID port
0x50, it is possible to see where the confusion starts.

In short, a write to 0xA0 is accepted by the GMBUS controller which we
interpreted as meaning the existence of a connection (a slave on the
other end of the wire ACKing the write). That was false.

During testing with a broken GMBUS implementation, which never reset an
earlier NAK, this test always reported a NAK and so we proceeded on to
the next test.

Reported-and-tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35904
Reported-and-tested-by:  Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=32612
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Keith Packard <keithp@keithp.com>
2011-04-05 09:05:34 -07:00
..
drm drm/i915/crt: Remove 0xa0 probe for VGA 2011-04-05 09:05:34 -07:00
stub gpu/stub: fix acpi_video build error, fix stub kconfig dependencies 2011-02-04 12:48:18 +10:00
vga Merge remote branch 'linus/master' into drm-intel-fixes 2011-01-24 18:27:32 +00:00
Makefile