From: Chris Wilson Date: Tue, 5 Apr 2011 15:04:39 +0000 (+0100) Subject: drm/i915/crt: Remove 0xa0 probe for VGA X-Git-Tag: v2.6.39-rc2~3^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0de009c900e7ebd21097797f723a40813e953879;p=pandora-kernel.git drm/i915/crt: Remove 0xa0 probe for VGA This is a moral revert of 6ec3d0c0e9c0c605696e91048eebaca7b0c36695. 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 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35904 Reported-and-tested-by: Riccardo Magliocchetti Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=32612 Signed-off-by: Chris Wilson Acked-by: Dave Airlie Signed-off-by: Keith Packard --- Reading git-diff-tree failed