[Intel-gfx] [PATCH] drm/i915: Handle YUV subpixel support better

[Ville Syrjälä]

On Mon, Mar 18, 2019 at 04:13:57PM +0100, Maarten Lankhorst wrote:
> Op 18-03-2019 om 15:18 schreef Ville Syrjälä:
> > On Mon, Mar 18, 2019 at 03:07:18PM +0100, Maarten Lankhorst wrote:
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/intel_sprite.c | 29 +++++++++++++++++++----------
> >>  1 file changed, 19 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> >> index 268fb34ff0e2..862fc172042f 100644
> >> --- a/drivers/gpu/drm/i915/intel_sprite.c
> >> +++ b/drivers/gpu/drm/i915/intel_sprite.c
> >> @@ -269,7 +269,8 @@ int intel_plane_check_src_coordinates(struct intel_plane_state *plane_state)
> >>  {
> >>  	const struct drm_framebuffer *fb = plane_state->base.fb;
> >>  	struct drm_rect *src = &plane_state->base.src;
> >> -	u32 src_x, src_y, src_w, src_h;
> >> +	u32 src_x, src_y, src_w, src_h, hsub, vsub;
> >> +	bool rotated = drm_rotation_90_or_270(plane_state->base.rotation);
> >>  
> >>  	/*
> >>  	 * Hardware doesn't handle subpixel coordinates.
> >> @@ -287,18 +288,26 @@ int intel_plane_check_src_coordinates(struct intel_plane_state *plane_state)
> >>  	src->y1 = src_y << 16;
> >>  	src->y2 = (src_y + src_h) << 16;
> >>  
> >> -	if (fb->format->is_yuv &&
> >> -	    (src_x & 1 || src_w & 1)) {
> >> -		DRM_DEBUG_KMS("src x/w (%u, %u) must be a multiple of 2 for YUV planes\n",
> >> -			      src_x, src_w);
> >> +	if (!fb->format->is_yuv)
> >> +		return 0;
> >> +
> >> +	/* YUV specific checks */
> >> +	if (!rotated) {
> >> +		hsub = fb->format->hsub;
> >> +		vsub = fb->format->vsub;
> >> +	} else {
> >> +		hsub = vsub = max(fb->format->hsub, fb->format->vsub);
> > Why this? From the looks of things there should be no need to deal with
> > rotation in this function at all.
> 
> I wrote a dumb test that fails if I rotate YUYV.
> 
> https://patchwork.freedesktop.org/patch/286170/
> 
> Corrupted image:
> 
> (kms_yuv:1155) igt_kms-DEBUG: display: A.0: plane_set_rotation(90°)
> (kms_yuv:1155) igt_kms-DEBUG: display: A.0: src_set_position(18,33)
> (kms_yuv:1155) igt_kms-DEBUG: display: A.0: src_set_size(44x65)
> (kms_yuv:1155) igt_kms-DEBUG: display: A.0: plane_set_position(64,64)
> (kms_yuv:1155) igt_kms-DEBUG: display: A.0: plane_set_size (256x256)
> 
> I had a 80x128 fb, only showing the center part which should be white, with a black border around it to cause CRC errors if we mess up clipping.
> 
> The scaling works fine, but the clipping does not in this case. I am getting a corrupted plane on screen which is mostly white, but with black dots in each tile.
> 
> Scaling just magnifies this corruption. :)

Hmm. I just poked my KBL a bit and it is also showing curious
behaviour. Even with 90/270 rotation it is in fact the TILEOFF
X coordinate that needs to be even (actually the hw just appears
to ignore the lsb). I can make the Y coordinate odd, and the image
still looks correct to my eyes. So feels like someone forgot to
to remove a (x&~1) from the hw when they added the 90/270 rotation,
and yet they went to the trouble of making odd Y coordinates work
correctly. Quite stange.

Width/height being odd seems to handled just fine by the hw.

-- 
Ville Syrjälä
Intel