Re: [PATCH] drm/i915/skl: Support Y tiling in MMIO flips

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Apr 21, 2015 at 10:05:46AM +0100, Tvrtko Ursulin wrote:
> 
> On 04/21/2015 05:55 AM, Jindal, Sonika wrote:
> >On 4/20/2015 11:14 PM, Daniel Vetter wrote:
> >>On Mon, Apr 20, 2015 at 05:38:20PM +0100, Tvrtko Ursulin wrote:
> >>>
> >>>On 04/20/2015 05:22 PM, Daniel Vetter wrote:
> >>>>On Mon, Apr 20, 2015 at 04:22:48PM +0100, Tvrtko Ursulin wrote:
> >>>>>From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>>>>
> >>>>>Add Y tiling support to skl_do_mmio_flip.
> >>>>>
> >>>>>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>>>>Cc: Damien Lespiau <damien.lespiau@intel.com>
> >>>>>Cc: Sonika Jindal <sonika.jindal@intel.com>
> >>>>>Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> >>>>>---
> >>>>>Looks like we completely missed this completely parallel instance
> >>>>>of plane
> >>>>>programming code when working on Y tiling support!
> >>>>>
> >>>>>Will rotation need supporting here as well?
> >>>>
> >>>>Oh dear this is a bit ugly. We definitely need either this for 4.1
> >>>>or take
> >>>>out the Y-tiling support for 4.1. Rotation only made 4.2, so I think
> >>>>we're good, but we do indeed need to take rotation into account here
> >>>>too.
> >>>
> >>>What is ugly, this patch or the overall situation?
> >>>
> >>>>And it seems like we also need a pile of igt testcases to make sure
> >>>>Y-tiling, rotation (even 180 probably) works correctly with
> >>>>pageflips. Yay
> >>>>for kms_flip growing even more.
> >>>
> >>>I added Y to kms_flip_tiling back then - but both that one and kms_flip
> >>>don't do any pipe crc. So not much use in automated fashion. And
> >>>testdisplay
> >>>apparently does not hit this path.
> >>>
> >>>I did not have working crc hw back then, maybe that has changed, I'll
> >>>check
> >>>it and then, depending on the outcome, see if I can add something
> >>>automated.
> >>>
> >>>Either way, adding this fix sounds better than reverting everything.
> >>
> >>On 2nd thought skl is still tagged as preliminary, so we don't have any
> >>issues here at all. Queued for -next, thanks for the patch.
> >>
> >>While looking at skl_do_mmio_flip I noticed though that rotation support
> >>seems to be completely absent. Or did I miss something?
> >Yes, it doesn't exist.
> >Is it because of it being temporary as per the following comment:
> >"/*
> >  * XXX: This is the temporary way to update the plane registers until
> >we get
> >  * around to using the usual plane update functions for MMIO flips
> >  */
> >"
> 
> Question is what are the prerequisites to start using plane update vfunc
> from here? Could we just do it now?

I'm not sure whether we can do some fancy intermediate step, in the end
we'll need async atomic plane updates so that we can use the helpers to
remap legacy page flips to atomic. But in any case if we don't fix this up
right away we need to track this as a blocker to lift skl prelimary hw
support. Adding Damien as an fyi.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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