[Intel-gfx] [PATCH 08/12] drm/i915: Add NV12 support to intel_framebuffer_init

[Konduru, Chandra]

> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Wednesday, May 20, 2015 12:37 AM
> To: Konduru, Chandra
> Cc: Daniel Vetter; intel-gfx at lists.freedesktop.org; Vetter, Daniel; Syrjala, Ville
> Subject: Re: [Intel-gfx] [PATCH 08/12] drm/i915: Add NV12 support to
> intel_framebuffer_init
> 
> On Tue, May 19, 2015 at 04:31:54PM +0000, Konduru, Chandra wrote:
> >
> >
> > > -----Original Message-----
> > > From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel
> Vetter
> > > Sent: Tuesday, May 19, 2015 1:24 AM
> > > To: Konduru, Chandra
> > > Cc: intel-gfx at lists.freedesktop.org; Vetter, Daniel; Syrjala, Ville
> > > Subject: Re: [Intel-gfx] [PATCH 08/12] drm/i915: Add NV12 support to
> > > intel_framebuffer_init
> > >
> > > On Sun, May 17, 2015 at 10:11:01PM -0700, Chandra Konduru wrote:
> > > > This patch adds NV12 as supported format to
> > > > intel_framebuffer_init and performs various checks.
> > > >
> > > > Signed-off-by: Chandra Konduru <chandra.konduru at intel.com>
> > > > Testcase: igt/kms_nv12
> > > > ---
> > > >  drivers/gpu/drm/i915/intel_display.c |   27
> +++++++++++++++++++++++++++
> > > >  1 file changed, 27 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > > b/drivers/gpu/drm/i915/intel_display.c
> > > > index 42924a6..41cd26f 100644
> > > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > > @@ -14043,6 +14043,33 @@ static int intel_framebuffer_init(struct
> > > drm_device *dev,
> > > >  			return -EINVAL;
> > > >  		}
> > > >  		break;
> > > > +	case DRM_FORMAT_NV12:
> > > > +		if (INTEL_INFO(dev)->gen < 9) {
> > > > +			DRM_DEBUG("unsupported pixel format: %s\n",
> > > > +				  drm_get_format_name(mode_cmd-
> > > >pixel_format));
> > > > +			return -EINVAL;
> > > > +		}
> > > > +		if (!mode_cmd->offsets[1]) {
> > > > +			DRM_DEBUG("uv start offset not set\n");
> > > > +			return -EINVAL;
> > > > +		}
> > >
> > > Nope. It's perfectly ok to have NV12 with a 0 offset for the uv plane, if
> > > it's e.g. in a separate buffer object. Which is the part this series seems
> > > to be completely missing - there's no code at all to look up (and store in
> > > intel_framebuffer the 2nd i915_bo pointer) the 2nd buffer handle afaics.
> > >
> > > You should also change your igts to use 2 separate buffers, just for test
> > > coverage.
> > > -Daniel
> >
> > Hi Daniel,
> > Agree, in general that is very well ok. But as skl hw requires uv to be after
> > y in gtt. This can be guaranteed by having a single bo and y and uv offsets
> > into it. Above sanity checks in i915 specific fb init call are for that reason.
> > There are definitely ways to guarantee uv to be after y even with two
> > separate bos (by uv remapping), but I see that is unnecessary
> > complication and not sure value by allowing that. Or am I missing
> > something here?
> 
> For a start you don't reject multiplane stuff where this isn't the case.
> And if we indeed have the hw requirement that the gtt address for y must
> be before the gtt address for uv (sounds strange to me, definitely need a
> bspec reference for that) then we need to check that throughroughly:
> Currently you could place Y after UV even in a single BO.

Hi Daniel,
NV12 programming is documented in bspec under display planes 
"Plane Planar YUV programming". There it talks about aux_dist
which is the distance between y and uv planes expecting uv to be
after y.

> 
> Also we need igts to make sure we catch userspace throwing invalid stuff
> at us.

Added a sub-test to kms_nv12 and will send out the updated igt patch.

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch