[Intel-gfx] How will Gfx driver support runtime PM on Haswell?

[Jesse Barnes]

On Wed, 21 Aug 2013 15:29:17 +0000
"Lin, Mengdong" <mengdong.lin at intel.com> wrote:

> Hi Ben,
> 
> How will Gfx driver support runtime PM on Haswell? Will the Gfx driver trigger "Adapter Power State" notification to BIOS when GPU switch state between D0 and D3?
> 
> We need to support RTD3 for HD-A legacy audio on Haswell Ultrabook. And this depends on Gfx driver to implement two BIOS notifications.
> 
> Here is the background of this dependency:
> The target of HD-Audio RTD3 is that BIOS can power off the on-board 3rd party audio codec to save power in S0. This would help to save ~60mW.
> Please note that audio driver cannot power off the codec, because the codec power is controlled by some GPIO which is board specific.
> 
> The BIOS will power off the audio codec when three requirements are met:
> 
> (1)     System is running on battery
> 
> (2)     HD-Audio controller is in D3. Means no active audio application is using the audio devices.
> 
> (3)     All displays are off. This means system is in "User-Absent Mode", and a long latency for devices to resume back to D0 is allowed, such as ~300ms to power on the audio codec.
> 
> For the 3rd requirement, BIOS needs Gfx driver to tell whether the system is in user-absent mode. It needs Gfx driver to triger two SCI SW notifications: Display Power State Notification and Adapter Power State Notification.
> 'Display Power State Notification' was implemented by Jani. But we were told that 'Adapter Power State' notification needs Gfx driver to support runtime PM at first.
> 
> So would you please share some information about runtime PM support in Gfx driver?

Paulo was going to test this on top of his PC8+ patchset.  AFAFIK the
only thing we  need to do is put the device into D3 when we enter the
PC8+ mode, and the BIOS will do the right thing (when we use the
OpRegion stuff Jani did anyway).

Paulo, are you still out celebrating the PC8 bits or have you had a
chance to try this yet?

-- 
Jesse Barnes, Intel Open Source Technology Center