[PATCH v2 6/6] drm/i915: Do not do fb src adjustments for NV12

[Srinivas, Vidya]

> -----Original Message-----
> From: Maarten Lankhorst [mailto:maarten.lankhorst at linux.intel.com]
> Sent: Monday, April 16, 2018 8:00 PM
> To: Srinivas, Vidya <vidya.srinivas at intel.com>; intel-gfx-
> trybot at lists.freedesktop.org
> Cc: Kamath, Sunil <sunil.kamath at intel.com>; Saarinen, Jani
> <jani.saarinen at intel.com>
> Subject: Re: [PATCH v2 6/6] drm/i915: Do not do fb src adjustments for
> NV12
> 
> Hmm, more thought about src adjustments...
> 
> Op 13-04-18 om 07:22 schreef Vidya Srinivas:
> > We skip src trunction/adjustments for
> > NV12 case and handle the sizes directly.
> > Without this, pipe fifo underruns are seen on APL/KBL.
> >
> > v2: For NV12, making the src coordinates multiplier of 4
> >
> > Credits-to: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Signed-off-by: Vidya Srinivas <vidya.srinivas at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 11 +++++++++++
> > drivers/gpu/drm/i915/intel_sprite.c  | 15 +++++++++++++++
> >  2 files changed, 26 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index bc83f10..f64708f 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -12978,6 +12978,10 @@ intel_check_primary_plane(struct
> intel_plane *plane,
> >  	bool can_position = false;
> >  	int ret;
> >  	uint32_t pixel_format = 0;
> > +	struct drm_plane_state *plane_state = &state->base;
> > +	struct drm_rect *src = &plane_state->src;
> > +
> > +	*src = drm_plane_state_src(plane_state);
> >
> >  	if (INTEL_GEN(dev_priv) >= 9) {
> >  		/* use scaler when colorkey is not required */ @@ -13001,6
> > +13005,13 @@ intel_check_primary_plane(struct intel_plane *plane,
> >  	if (!state->base.fb)
> >  		return 0;
> >
> > +	if (pixel_format == DRM_FORMAT_NV12) {
> > +		src->x1 = (((src->x1 >> 16)/4)*4) << 16;
> > +		src->x2 = (((src->x2 >> 16)/4)*4) << 16;
> > +		src->y1 = (((src->y1 >> 16)/4)*4) << 16;
> > +		src->y2 = (((src->y2 >> 16)/4)*4) << 16;
> > +	}
> 
> Lets reject non multiple of 4 coordinates for plane_state's src_x and src_y,
> and before adjustment also reject non multiple of 4 src_w/src_h.fter that
> we can also reject clipping to the right/bottom edge of the screen, if the
> pipe_src_w/h is not a multiple of 4. That way an application trying to go
> beyond the screen.

kms_plane_scaling and some other tests during execution generate lots of 
non mult of 4 buffer width/height. All these tests will show fail in the IGT BAT.
In some cases, even thought the width and height will be multiple of 4 before the
Adjustment (say our 16x16 buffer), this after adjustment becomes a 15 in intel_check_sprite_plane.
This again would cause underrun. If we reject non multiple of 4s in our skl_update_scaler also,
then even simple tests with 16x16 like rotation will fail due to it getting adjusted.

> 
> skl_check_plane_surface could do all the fixups and is allowed to return an
> error code, so we could put all SKL specific NV12 handling in there.
> It doesn't matter that we calculate potentially illegal values, if we never
> program them and return -EINVAL there. If it turns out we've been too
> paranoid we could relax the condition.
> 
> This would mean unified handling for NV12 for primary and sprite. :)
> 
> >  	if (INTEL_GEN(dev_priv) >= 9) {
> >  		ret = skl_check_plane_surface(crtc_state, state);
> >  		if (ret)
> > diff --git a/drivers/gpu/drm/i915/intel_sprite.c
> > b/drivers/gpu/drm/i915/intel_sprite.c
> > index 8b7947d..c1dd85e 100644
> > --- a/drivers/gpu/drm/i915/intel_sprite.c
> > +++ b/drivers/gpu/drm/i915/intel_sprite.c
> > @@ -1035,11 +1035,20 @@ intel_check_sprite_plane(struct intel_plane
> *plane,
> >  			return vscale;
> >  		}
> >
> > +		if (fb->format->format == DRM_FORMAT_NV12) {
> > +			if (src->x2 >> 16 == 16)
> > +				src->x2 = 16 << 16;
> > +			if (src->y2 >> 16 == 16)
> > +				src->y2 = 16 << 16;
> This part doesn't look required, the magic below for the nv12 format is
> similar.. Just conditionally call adjust_size for format != NV12. :)
> > +			goto nv12_min_no_clip;
> > +		}
> > +
> >  		/* Make the source viewport size an exact multiple of the
> scaling factors. */
> >  		drm_rect_adjust_size(src,
> >  				     drm_rect_width(dst) * hscale -
> drm_rect_width(src),
> >  				     drm_rect_height(dst) * vscale -
> drm_rect_height(src));
> >
> > +nv12_min_no_clip:
> >  		drm_rect_rotate_inv(src, fb->width << 16, fb->height << 16,
> >  				    state->base.rotation);
> >
> > @@ -1105,6 +1114,12 @@ intel_check_sprite_plane(struct intel_plane
> *plane,
> >  		src->x2 = (src_x + src_w) << 16;
> >  		src->y1 = src_y << 16;
> >  		src->y2 = (src_y + src_h) << 16;
> > +		if (fb->format->format == DRM_FORMAT_NV12) {
> > +			src->x1 = (((src->x1 >> 16)/4)*4) << 16;
> > +			src->x2 = (((src->x2 >> 16)/4)*4) << 16;
> > +			src->y1 = (((src->y1 >> 16)/4)*4) << 16;
> > +			src->y2 = (((src->y2 >> 16)/4)*4) << 16;
> > +		}