[Nouveau] v4.12 backport request: 13a86519202 (drm/nouveau/i2c/gf119-: add support for address-only transactions)

Ilia Mirkin imirkin at alum.mit.edu
Sun Sep 3 15:46:57 UTC 2017

Commit df8dc97cd17 (drm/nouveau/kms/nv50: use drm core i2c-over-aux
algorithm) switched things over to the drm algo. Unfortunately it
generates address-only transactions. Prior to GF119, the hardware had
no support for such things, and GF119+ the nouveau code did not handle
these properly.

The result of this bug is that EDID doesn't make it over for DP (and
eDP) screens, which in turn wreaks all sorts of havoc. There have been
lots of reports on IRC, a few on mailing lists, and also:


Commit 13a86519202 (drm/nouveau/i2c/gf119-: add support for
address-only transactions) fixes the nouveau support for such
transactions on GF119+ and flips things back over to the custom algo
for earlier chips. Please include into the next v4.12.x release:

commit 13a86519202c5d119d83640d6f781f3181205d2c
Author: Ben Skeggs <bskeggs at redhat.com>
Date:   Wed Jul 19 16:49:59 2017 +1000

    drm/nouveau/i2c/gf119-: add support for address-only transactions

    Since switching the I2C-over-AUX helpers, there have been regressions on
    some display combinations due to us not having support for "address only"

    This commits enables support for them for GF119 and newer.

    Earlier GPUs have been reverted to a custom I2C-over-AUX algorithm.

    Signed-off-by: Ben Skeggs <bskeggs at redhat.com>

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