[PATCH v4 00/11] Enabling 180 degree rotation for sprite and crtc planes

[Daniel Vetter]

On Mon, Feb 10, 2014 at 04:29:45PM +0200, Ville Syrjälä wrote:
> On Mon, Feb 10, 2014 at 02:14:54PM +0000, One Thousand Gnomes wrote:
> > > > Does this mean it should also handle horizontal mirroring in
> > > > hardware (180° rotate, and scan lines backwards combined) ?
> > > 
> > > Our hardware doesn't support mirroring (h or v). Well, unless you
> > > count h+v mirroring since that's 180 degree rotation :)
> > > 
> > > Anyways IIRC the old video overlay (present on gen2-4) was the only plane
> > > to ever support mirroring on Intel hardware. With all other planes we're
> > > limited to 0 and 180 degree rotation
> > 
> > It seems to do vertical mirroring providing your output buffer is
> > allocated and aligned on page boundaries as the GTT can then be used to
> > map the scan lines in any order you like ?
> 
> Oh, right. That would be possible, but that sounds like something that
> needs to be done on the gem side rather than the kms side since it
> impacts other things besides scanout memory access. Well either that
> or we'd potentially need to map the same object multiple times into
> the ggtt.

Until someone demonstrates a clear benefit and use-case for that I'll vote
"pls just blit it with the render engine". The common use-case for
rotation is tablets/phones and there we can't do it in many cases anyway.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch