-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Friday, October 25, 2013 7:42 PM
We want to enable display power well management on Batrail platform
(Valleyview SOC), similar to what we did on Haswell.
Would you please check if our ideas are ok and give some advice?
For Valleyview/VLV the display controller has a power well island. When
display is off, the display island can be power gated.
Unlike Haswell, the VLV HD-A controller is not in the display power well. The
controller is in south bridge and shared by multiple codecs, same as the predecessors of Haswell.
But the power is still controlled based on the usage of HD-audio controller, not per codec, isn't it? If so, we can keep using the runtime PM implementation.
Reading again your mail, it sounds like we need the i915 power up/down *just for HDMI codec*, not for onboard audio, while both of them are connected over the same HD-audio bus (i.e. controller). If it's the case, an easiest way is to put i915_request_power_well*() at set_power_state callback as you pointed.
I don't like an idea to add pre_resume and post_suspend opts again.
Yes, the i915 power up/down is just for the HDMI codec. The audio controller and on-board codec are not affected. So we'll try the 1st option and see if it can work as we expected.
Thanks for your advice! Mengdong