[Precise][SRU][PATCH 1/1] drm/i915: Periodically sanity check power management

[Leann Ogasawara]

On 03/07/2013 12:46 PM, Seth Forshee wrote:
> On Thu, Mar 07, 2013 at 12:14:55PM -0800, leann.ogasawara at canonical.com wrote:
>> From: Chris Wilson <chris at chris-wilson.co.uk>
>>
>> BugLink: http://bugs.launchpad.net/bugs/1146425
>>
>> Every time we use the device after a period of idleness, check that the
>> power management setup is still sane. This is to workaround a bug
>> whereby it seems that we begin suppressing power management interrupts,
>> preventing SandyBridge+ from going into turbo mode.
>>
>> This patch does have a side-effect. It removes the mark-busy for just
>> moving the cursor - we don't want to increase the render clock just for
>> the sprite, though we may want to bump the display frequency. I'd argue
>> that we do not, and certainly don't want to take the struct_mutex here
>> due to the large latencies that introduces.
> Regarding this last paragraph: The upstream commit does remove a call to
> intel_mark_busy() from intel_crtc_update_cursor(), which I suspect is
> what this refers to. That call is present in our precise kernel but is
> not removed by this patch. Do you know whether or not that omission was
> intentional?

Hi Seth,

After checking with Intel, the ommission was intentional.  According to
Intel, there are multiple Gen6+ related rps issues which are fixed in
the upstream kernel.  The Precise kernel unfortunately does not have all
of these fixes applied.  Intel states that it is only safe to remove the
call to intel_mark_busy() after having applied all the rps fixes. 
Unfortunately, all of the rps fixes may not be acceptable for Precise
SRU so as it stands the call to intel_mark_busy() needs to  remain present.

Thanks,
Leann