[Intel-gfx] [resend] i915: high power consumption after suspend/resume

Andrew Lutomirski luto at mit.edu
Fri Oct 30 19:55:57 CET 2009

On Fri, Oct 30, 2009 at 11:37 AM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> On Fri, 30 Oct 2009 02:25:21 -0400
> Andrew Lutomirski <luto at mit.edu> wrote:
>> On Thu, Oct 29, 2009 at 1:40 PM, Andrew Lutomirski <luto at mit.edu>
>> wrote:
>> >
>> > I just suspended and resumed and power consumption stayed low.  I'll
>> > try and get an intel_reg_dumper diff next time I trigger this bug.
>> intel_reg_dumper blames RENCLK_GATE_D2.  Patch coming.
>> Maybe my BIOS doesn't always reset it.
> Does resetting that reg get your power savings back?

Surprisingly, no.  With my kernel patched to restore it on resume, I
still see high power consumption, and rebinding still fixes it.  (As
an aside, I think hat i915's ability to survive rebinding without
crashing on the next X startup has gotten worse recently.  I
invariably OOPS awhile after rebinding with recent kernels.)

I diffed the output of intel_reg_dumper (2.9.0, I think):

--- /tmp/pre-rebind     2009-10-30 14:35:24.267236469 -0400
+++ /tmp/post-rebind    2009-10-30 14:39:22.649986477 -0400
@@ -46,7 +46,7 @@
 (II):         PFIT_CONTROL: 0x00000000
 (II):      PFIT_PGM_RATIOS: 0x00000000
 (II):      PORT_HOTPLUG_EN: 0x3e040320
-(II):    PORT_HOTPLUG_STAT: 0x38560800
+(II):    PORT_HOTPLUG_STAT: 0x38000000
 (II):             DSPACNTR: 0x00000000 (disabled, pipe A)
 (II):           DSPASTRIDE: 0x00000000 (0 bytes)
 (II):              DSPAPOS: 0x00000000 (0, 0)
@@ -149,7 +149,7 @@
 (II):          FBC_COMMAND: 0x08c80034
 (II):           FBC_STATUS: 0x00000000
 (II):         FBC_CONTROL2: 0x00000000
-(II):        FBC_FENCE_OFF: 0x00008000
+(II):        FBC_FENCE_OFF: 0x10000000
 (II):          FBC_MOD_NUM: 0x00000060
 (II):              MI_MODE: 0x00000200
 (II):         MI_ARB_STATE: 0x00000040

intel_reg_write doesn't seem to work right on FBC_FENCE_OFF (previous
value doesn't agree w/ intel_reg_dumper), and I'm not sure exactly
what that's supposed to do.


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