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Bug#597358: xserver-xorg-video-radeon: Screen brightness flickers when KMS is enabled


Aaron Small wrote[1]:

> When KMS is enabled, the screen is mostly correct all the time, but the
> brightness for either the entire screen, or one horizontal line
> flickers, maybe two to three times per second. Sometimes the change in
> brightness is just noticeable, and sometimes it is strong enough to look
> like a horizontal line the full width of the display becomes white.

Alex Deucher wrote:

> Can you try this set of kernel patches?
> Yes, it will affect all radeons, but in practice it's should really
> only change things on avivo hw (r5xx+) due to the limited number of
> post dividers on pre-avivo hardware.  It's the same algo that was used
> originally on all radeons, before I added the newer algo; the only
> tweak is that we prefer higher post dividers rather than lower ones.
> In practice, it seems the older one works better.  I've tested them on
> a variety of monitors on all my radeon cards (r1xx-evergreen
> families). Additionally these patches have fixed several bugs where
> the newer algo did not work properly.

Aaron Small wrote (after testing on top of "master"):

> Yes, these patches fix the problem.

Stefan, do these three patches look like reasonable candidates for the
linux-2.6.32.y-drm33.z tree?  They are straightforward backports of
patches from mainline (so please feel free to skip the patches and
cherry-pick them for yourself :)).  This series doesn't include
"drm/radeon/kms: remove new pll algo" because in 2.6.33 the newer algo
hadn't been introduced yet.

Aaron, if you get a chance to test this series on top of the squeeze
kernel, that would be interesting of course. :)

Alex Deucher (2):
  drm/radeon/kms: prefer high post dividers in legacy pll algo
  drm/radeon/kms: remove some pll algo flags

Dan Carpenter (1):
  drm: radeon: fix sign bug

 drivers/gpu/drm/radeon/atombios_crtc.c      |   14 +---------
 drivers/gpu/drm/radeon/radeon_display.c     |   36 ++++++---------------------
 drivers/gpu/drm/radeon/radeon_legacy_crtc.c |    5 ---
 drivers/gpu/drm/radeon/radeon_mode.h        |   12 ++------
 4 files changed, 12 insertions(+), 55 deletions(-)

Looking forward to your thoughts,

[1] http://bugs.debian.org/597358

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