Radeon DPMS problems? backlight turns back on after a minute

Lowell Alleman lowell at allemansonline.com
Tue Apr 7 06:31:58 PDT 2009

On Tue, Apr 7, 2009 at 3:05 AM, Magnus Kessler <Magnus.Kessler at gmx.net> wrote:
> On Tuesday 07 April 2009, Lowell Alleman wrote:
>> Are there any known issues with DPMS not working properly with the latest
>> radeon driver?  I've found some old bugs that sound similar, but don't
>> exactly match and the workarounds I've found seem to make a difference.
>>  Here is what I'm experiencing:
>> My laptop (IBM T42, r300) LCD will not going into power saving mode on
>> its own.  If I force it go into one of these modes, it only stays in that
>> mode for a short period of time (a few seconds to a couple of minutes)
>> before the screen turns back on again. I'm pretty sure this isn't due to
>> any keyboard/mouse events (since the screen saver doesn't
>> pop up a login dialog) and I don't see any new events /var/log/acpid that
>> correlate to the LCD being re-enabled.  However, every time the LCD turns
>> back on, I do see the following message in the Xorg.0 log file:  "enable
>> LVDS".  It appears that the X server still thinks that the DPMS mode is
>> enabled, because "xset q" says that the monitor is still in "Suspend" (or
>> whatever mode I forced it to be in) even after the LCD was turned on
>> again.
>> Here are some additional details about my setup, and what I've tried:
>> Relevant output from "xset q":
>> DPMS (Energy Star):
>>  Standby: 600    Suspend: 660    Off: 1200
>>  DPMS is Enabled
>>  Monitor is On
>> After the display has been disabled using "xset force suspend" the
>> display shuts down.  If you check "xset q" it now reports "Monitor is in
>> Suspend". A minute or so later the LCD is turned back on.  Now I can see
>> screensaver (which is DPMS-aware, and therefore has been paused to save
>> CPU cycles).  At this point, "xset q" still shows "Monitor is in
>> Suspend".
>> I've tried switching between EXA and XAA acceleration.  As of radeon
>> v6.12.0 XAA says it is not supported any more, but EXA doesn't appear to
>> be the default yet.  (Not sure what that means; but in both cases this
>> problems still occurs).  I've also tried adding the "NoPM" option, as I
>> found as an old workaround suggested, but that didn't make a difference
>> either.
>> Versions:
>> X.Org X Server 1.5.2
>> Radeon driver:  6.12.0  (I compiled this locally for improved
>> performance in latest release)
>> Linux 2.6.27-11-generic #1 SMP Thu Jan 29 19:24:39 UTC 2009 i686
>> GNU/Linux Kubuntu 8.10
>> KDE 4.1.4
>> I can provide additional info (xorg.conf and Xorg.0.log) if this is an
>> unknown situation and those would be helpful to have.
>> Thanks,
>> - Lowell
> Hi Lowell,
> this was a bug in the KDE 4 screensaver code [0]. It is certainly fixed in
> the latest version of KDE. Try updating to KDE 4.2.1 or above.
> HTH,
> Magnus
> [0] http://bugs.kde.org/show_bug.cgi?id=165265
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Hey Magnus,

Thanks for that link.  I do think that that bug is *part* of my
problem, but not *all* of it.  (I plan on upgrading to Kubuntu 9.04,
which has KDE 4.2.x once it is released last this month.)  Based on
the info in that bug report, I ran the following test:

I set my screen saver to come on after 5 minutes.  Then I ran "xset
dpms 5 10 15".  The screen does blank after 5 seconds, but it then
comes back on after about 2 seconds, with the screen saver visible in
the background (which was unexpected.)  Then at the 10 second mark,
the screen turns off again and comes back on after a few minutes.

One general observation is that it seems like the first time the LCD
enters a power saving mode, it lasts for only a few seconds.  Then
each additional switch into powersavings mode lasts for about a minute
or two.  (When I say "first time", I mean after an Xorg restart.)

Just to rule out KDE as the whole problem, I'm going to try starting
up in a different environment; perhaps some failsafe xterm mode.  I'll
let you know what I find.

- Lowell

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