[Bug 93471] [radeonsi] power consumption on pitcairn card stays high after 2. monitor disconnected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93471

            Bug ID: 93471
           Summary: [radeonsi] power consumption on pitcairn card stays
                    high after 2. monitor disconnected
           Product: DRI
           Version: XOrg git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: onlineservices at marwedels.de

Created attachment 120641
  --> https://bugs.freedesktop.org/attachment.cgi?id=120641&action=edit
drm part of dmesg

When starting the PC with a single monitor, the power consumption is about 60W
(was 50-55W with a HD4650 before).

cat /sys/kernel/debug/dri/64/radeon_pm_info
uvd    vclk: 0 dclk: 0
power level 0    sclk: 30000 mclk: 15000 vddc: 900 vddci: 850 pcie gen: 2

When adding a second monitor the power consumption stays at this level until
its get activated.
Once activated (xrandr --output HDMI-0 --auto), the consumption ramps up to
79W.

cat /sys/kernel/debug/dri/64/radeon_pm_info
uvd    vclk: 0 dclk: 0
power level 0    sclk: 30000 mclk: 120000 vddc: 900 vddci: 1000 pcie gen: 2

Disabling the second monitor again (xrandr --output HDMI-0 --off), does not
reduce the consumption again. Not even unplugging helps.
While I read that its simply not possible to get the low power with two active
monitors, could it be possible to manually or
automatically switch to the previous clock if all but one monitor have been
disabled?
Moreover could the signal simply be cloned without consuming +29W if resolution
and refresh rate are equal?
The second monitor is a projector permanently connected, but switched off 90%
of the time.

Xorg: From Debian 8.1 stable
Kernel: 4.3.3
Card (bought as R7 370): VGA compatible controller: Advanced Micro Devices,
Inc. [AMD/ATI] Curacao PRO [Radeon R9 270] (rev 81)

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