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            <b><a class="bz_bug_link 
          bz_status_ASSIGNED "
   title="ASSIGNED - [IVB] FBC increases power for libva video workload"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=65396#c23">Comment # 23</a>
              on <a class="bz_bug_link 
          bz_status_ASSIGNED "
   title="ASSIGNED - [IVB] FBC increases power for libva video workload"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=65396">bug 65396</a>
              from <span class="vcard"><a class="email" href="mailto:zhixinx.liu@intel.com" title="zhixinx.liu <zhixinx.liu@intel.com>"> <span class="fn">zhixinx.liu</span></a>
</span></b>
        <pre>(In reply to Jani Nikula from <a href="show_bug.cgi?id=65396#c21">comment #21</a>)
<span class="quote">> Please retest with current nightly.</span >

ignore my last commit.

virify FBC function with kernel3.17.0_drm-intel-nightly_ead7d7_20141013. and we
found that:
For HSW=>
    Save power when running idle/browser/video workload after enable FBC. 
    Not save power when running game workload after enable FBC. 
For IVB=>
    Cannot enable FBC with IVB.
    When set i915.enable_fbc=1 or i915.enable_fbc=0, after reboot and start X, 
    check the FBS status that it's always disable. log:
        [root@x-ivb16 opt]# cat /sys/kernel/debug/dri/0/i915_fbc_status
        FBC disabled: multiple pipes are enabled
    It's new design or issue?

Test result:
----------------------------------------      
HSW-ult      FBC disable Average_watt       FBC enable Average_watt          
idle         11.0                           10.9 
browser      14.1                           14.0
video        13.2                           12.8
game         20.6                           20.6

Test Env:
Arch:              x86_64
Libdrm:            (master)libdrm-2.4.56
Mesa:              (10.3)9f67c26d1b424b8f3d86b5435c8f74d0a81eb86d
Xserver:           (server-1.16-branch)xorg-server-1.16.0
Xf86_video_intel:  (master)2.99.914
Libva:             (master)e0d25ece01e7aba819c910e98c4fb4706cdab055
Libva_intel_driver:(master)e02449a1d65b44a82b5f2fcdf8a5b0ba51c2bb6a
Ffmpeg:            (master)1b5ccae0f2045ac86bc9e1257cec1b3fba81315f
Mplayer:           (hwaccel-vaapi)1923fa10ed77bbf8408f2ce312d85a97dab1f0f3
Glib:              (master)3b8bc8bacf1fe31cda44fb5293711e87989388ea
Gstreamer10:       (1.2)861ca3d6787d84c9bea7110cb46821e9b8f63aff
Gst_plugins_base10:(1.2)df7e7daa29ba14447b4d8dd43c35d8a3ad9e4984
Gst_plugins_good10:(1.2)e0417c28d56ac64a2e8d149bbaf812d2ce227153
Gst_plugins_bad10: (1.2)277b8c34e7214177764833b73f17e43ced496f8f
Gst_plugins_ugly10:(1.2)2233d97e6ad1a3988d9a9ca0fc0cf00ec4031a8f
Gst_plugins_vaapi10:(master)406aa37373e2b9917714eccd2834a45d18b61fd1</pre>
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