[Intel-gfx] [PATCH 2/2] drm/i915/vlv: Replaced Blitter ring based flips with MMIO Flips for VLV.

[Goel, Akash]

>> As Chris said, instead of rolling your own code to track when flips are emitted to the ring, simply add a real request (with the add_request function) 
>> like the execbuf paths. Then add any additional trackin you need to our request structure.
>> -Daniel

I am really sorry, but I am still not able to get it. 
Earlier when we were adding a MI_DISPLAY_FLIP command in the blitter ring,  the cross ring MBOX synchronization at Hw level ensured that Flip command will get parsed/executed by BCS, only after the rendering has completed on RCS.
But now with MMIO based flips, before updating the Display Surface register, we somehow need to wait for the rendering to get completed. But we want to avoid synchronous wait in the Page flip call. So we call the 'wait_seqno' from the context of a worker thread  & once the wait is completed we update the plane register to effect a flip.
I am not able to understand that how the 'add_request' will help here.

Best Regards
Akash

-----Original Message-----
From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
Sent: Friday, February 07, 2014 8:17 PM
To: Goel, Akash
Cc: 'Chris Wilson'; 'intel-gfx at lists.freedesktop.org'
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915/vlv: Replaced Blitter ring based flips with MMIO Flips for VLV.

On Fri, Feb 07, 2014 at 11:59:29AM +0000, Goel, Akash wrote:
> Please could you kindly elaborate here, it will help us to proceed further with this patch.

As Chris said, instead of rolling your own code to track when flips are emitted to the ring, simply add a real request (with the add_request
function) like the execbuf paths. Then add any additional trackin you need to our request structure.
-Daniel

> 
> Best Regards
> Akash
> 
> -----Original Message-----
> From: Goel, Akash
> Sent: Monday, January 13, 2014 3:17 PM
> To: Chris Wilson
> Cc: intel-gfx at lists.freedesktop.org
> Subject: RE: [Intel-gfx] [PATCH 2/2] drm/i915/vlv: Replaced Blitter ring based flips with MMIO Flips for VLV.
> 
> >> Rather exporting deep magic from i915_gem, just emit the request after the mmio flip and use the normal signalling mechanisms. There are other users who could also use a request after a flip.
> 
> Sorry, couldn't understand your point.
> 
> With Command streamer based flips, we could use the cross ring MBOX mechanism at Hw level, to ensure that buffer is flipped only when the rendering is completed. 
> 
> But with MMIO flips, need to ensure that we somehow introduce a wait for the rendering to complete, before updating the Display Surface Address register, to effect the flip. 
> 
> Best Regards
> Akash
> 
> -----Original Message-----
> From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> Sent: Thursday, January 09, 2014 5:02 PM
> To: Goel, Akash
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915/vlv: Replaced Blitter ring based flips with MMIO Flips for VLV.
> 
> On Thu, Jan 09, 2014 at 04:56:39PM +0530, akash.goel at intel.com wrote:
> > From: Akash Goel <akash.goel at intel.com>
> > 
> > Using MMIO based flips now on VLV for Media power well residency optimization.
> > The blitter ring is currently being used just for the command 
> > streamer based flip calls. For pure 3D workloads, with MMIO flips, 
> > there will be no use of blitter ring and this will ensure the 100% residency in D0i3 for Media well.
> > The other alternative of having Render ring based flip calls is not 
> > being used, as that option adversly affects the performance (FPS) of 
> > certain 3D Apps
> 
> Rather exporting deep magic from i915_gem, just emit the request after the mmio flip and use the normal signalling mechanisms. There are other users who could also use a request after a flip.
> -Chris
> 
> --
> Chris Wilson, Intel Open Source Technology Centre 
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> Intel-gfx at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch