On Wed, May 21, 2014 at 5:56 PM, Babu, Ramesh <ramesh.babu@xxxxxxxxx> wrote: >> On Tue, May 20, 2014 at 05:29:07PM +0300, Imre Deak wrote: >> > On Tue, 2014-05-20 at 05:52 +0300, Lin, Mengdong wrote: >> > > This RFC is based on previous discussion to set up a generic >> > > communication channel between display and audio driver and an >> > > internal design of Intel MCG/VPG HDMI audio driver. It's still an >> > > initial draft and your advice would be appreciated to improve the >> > > design. >> > > >> > > The basic idea is to create a new avsink module and let both drm and >> > > alsa depend on it. >> > > This new module provides a framework and APIs for synchronization >> > > between the display and audio driver. >> > > >> > > 1. Display/Audio Client >> > > >> > > The avsink core provides APIs to create, register and lookup a >> > > display/audio client. >> > > A specific display driver (eg. i915) or audio driver (eg. HD-Audio >> > > driver) can create a client, add some resources objects (shared >> > > power wells, display outputs, and audio inputs, register ops) to the >> > > client, and then register this client to avisink core. The peer >> > > driver can look up a registered client by a name or type, or both. >> > > If a client gives a valid peer client name on registration, avsink >> > > core will bind the two clients as peer for each other. And we expect >> > > a display client and an audio client to be peers for each other in a >> > > system. >> > >> > One problem we have at the moment is the order of calling the system >> > suspend/resume handlers of the display driver wrt. that of the audio >> > driver. Since the power well control is part of the display HW block, >> > we need to run the display driver's resume handler first, initialize >> > the HW, and only then let the audio driver's resume handler run. For >> > similar reasons we have to call the audio suspend handler first and >> > only then the display driver resume handler. Currently we solve this >> > using the display driver's late/early suspend/resume hooks, but we'd >> > need a more robust solution. >> > >> > This seems to be a similar issue to the load time ordering problem >> > that you describe later. Having a real device for avsync that would be >> > a child of the display device would solve the ordering issue in both >> > cases. I admit I haven't looked into it if this is feasible, but I >> > would like to see some solution to this as part of the plan. >> >> If we are able create and mandate that HDMI display controller is parent and >> audio is child device, then this wouldn't be an issue and PM frameowrk will >> ensure parent is suspended last. >> > If there is a scenario where HDMI audio has to active but display has to go to low power, then > parent-child device is not optimal. There needs to be a mechanism to turn on/off individual hw blocks within > the controller. Our gfx runtime pm code is a _lot_ better than that. We track each power domain individually and enable/disable them only when need. armsoc drivers could do the same or make sure that the avsink device is a child of the right block. Of course if your driver only has binary runtime pm and fires up everything then we have a problem. But imo that's a problem with that driver, not with making avsink real devices as children of something. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
