[Bug 72385] New: [Power][turbo]GPU peak frequency can't reach peak immediately as exceptedly

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=72385

          Priority: medium
            Bug ID: 72385
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: [Power][turbo]GPU peak frequency can't reach peak
                    immediately as exceptedly
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: major
    Classification: Unclassified
                OS: Linux (All)
          Reporter: shengyanx.zhao at intel.com
          Hardware: All
            Status: NEW
           Version: XOrg CVS
         Component: DRM/Intel
           Product: DRI

Test Env:
------------------------------------
Platform:               HSW
Arch:                   x86
OS:                     Fedora 19
Xserver:                (server-1.14-branch)xorg-server-1.14.4.901
Xf86_video_intel:               (master)2.99.906
Kernel:                  kernel-3.12.2_20131203+-2.x86_64


Reproduced Steps:
------------------------------------
1. rpm -ivh kernel-3.12.2_20131203+-2.x86_64.rpm
2. Start up X.
3. Check the minimum frequency: cat /sys/class/drm/card0/gt_min_freq_mhz
4. Check the maximum frequency：cat /sys/class/drm/card0/gt_max_freq_mhz
5. Check the current frequency: cat /sys/class/drm/card0/gt_cur_freq_mhz
6. Start glxgears && cat /sys/class/drm/card0/gt_cur_freq_mhz
7. Stop glxgears && cat /sys/class/drm/card0/gt_cur_freq_mhz


The expected phenomenon should be: when start glxgears, the current frequency
should be reach to max frequency(e.g. 1100MHz), when stop glxgears, the current
frequency should be fall down to minimum frequency(e.g. 200MHz) quickly.
However, actually, when we start glxgears, we cat
/sys/class/drm/card0/gt_cur_freq_mhz and got frequency remain minimum value,
after 30 mins, the value reach to peak value. At this time, when we kill
glxgears, the peak value fall down a little(e.g. 100HMz, from 1100MHz to
1000MHz) instead of our expected minimum value(e.g. 200MHz).



Reproduced Rate:
------------------------------------
100%

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