linux-kernel - Re: [PATCH v4 00/11] Enabling 180 degree rotation for sprite and crtc planes

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Date:	Mon, 10 Feb 2014 18:31:14 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	sagar.a.kamble@...el.com, daniel.vetter@...ll.ch,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	vijay.a.purushothaman@...el.com, tomi.valkeinen@...com,
	dri-devel@...ts.freedesktop.org, gregkh@...uxfoundation.org,
	joe@...ches.com, airlied@...hat.com
Subject: Re: [PATCH v4 00/11] Enabling 180 degree rotation for sprite and
 crtc planes

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
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