[Bug 102511] RV770 error on change dpm balanced<->battery

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102511

--- Comment #2 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to Rob MacKinnon from comment #0)
> * Actual Result:
> - DPMS change level changes as expected.
> - Dmesg:
> [ 3302.814889] [drm:btc_dpm_set_power_state [radeon]] *ERROR*
> rv770_restrict_performance_levels_before_switch failed
> [ 3316.661933] [drm:btc_dpm_set_power_state [radeon]] *ERROR*
> rv770_restrict_performance_levels_before_switch failed
> 
> * Expected result:
> - DPMS change level changes as expected.
> - No error messages in dmesg.

Are you actually experiencing any problems?  I think the error message may be
harmless can could probably be removed.

> 
> * Additional Info:
> Also, not sure if this is related or not, when switching from "battery" to
> "performance" there sometimes appears to be an initial clocking issue (which
> I believe is related to #93753). Switching back and forth a few times seems
> to clean it.  Unsure the cause.  Another note, upon further inspection of my

There is no real balanced state.  It's either battery or performance depending
on whether the chip is on ac or dc power.  The only real states you can switch
between are performance and battery.  I need to see the output of our dmesg
with radeon.dpm=1 to see what states your vbios provides.

> DPMS settings, I noticed the drastic differences between "balanced" and
> "battery" `sclk`s. My understand (which could be faulty) is that `sclk`
> drives the clocking for single displays, while `mclk` for multiple. My

sclk is the 3D engine clock.  mclk is the memory clock.  mclk switching is
disabled when multiple displays are active since the switch has to happen
during the display's vblank period otherwise you'd see display glitches.  With
multiple displays, the vblank periods are not likely to align so mclk switching
is disabled.

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