linux-stable.git/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crc.c, branch v4.18.2

drm/amd/display: Skip 2 frames when first reading CRC

2018-02-19T19:20:11+00:00

Skipping the first frame will prevent uncoooked values most of the time.
However, in some unlikely cases, the second frame will be uncooked as
well.

Signed-off-by: Leo (Sunpeng) Li 
Reviewed-by: Harry Wentland 
Signed-off-by: Alex Deucher

drm/amd/display: When enabling CRC, disable dither & enable truncation

2018-02-19T19:20:09+00:00

When user-mode is using 8bpc, the hardware represents it internally
using a higher bit depth. This causes problems when comparing CRCs for
color managment tests.

We need to disable dithering as well, since it makes CRC values
non-deterministic.

It's easy to see why dithering needs to be disabled, The reason why
truncation also needs to be enabled is better described with an example.
Consider the folowing which tests the color transform matrix (CTM):

Expected CRC = FB_A -> Degamma (Bypassed) -> CTM (Bypassed)
                                                  |
                                                  v
                            Obtain CRC  <- Regamma(Bypassed)

Actual CRC = FB_B -> Degamma (Bypassed) -> CTM (0.5*Identity)
                                                  |
                                                  v
                            Obtain CRC  <- Regamma(Bypassed)

FB_A contains a solid red color at half intensity (127 @ 8bpc)
FB_B contains a solid red color at full intensity (255 @ 8bpc)

We expect that Expected CRC = Actual CRC, but that's not the case. When
the CTM is applied, the output is at half intensity, but also at a
higher bit depth within hardware. i.e. 255/2 = 127.5: not representable
in 8bpc, but can be at 10bpc. This causes the two CRC's to be different.

The solution is to truncate the output bit depth to the same as input
when enabling CRC capture. Since Linux only supports 8bpc, hard code
that for now.

Signed-off-by: Leo (Sunpeng) Li 
Reviewed-by: Harry Wentland 
Signed-off-by: Alex Deucher

drm/amd/display: Early return on crc get

2018-02-19T19:18:34+00:00

If crc is disabled, early return when getting crc's. That way, we avoid
reading extra registers within the pflip high irq.

Signed-off-by: Leo (Sunpeng) Li 
Reviewed-by: Harry Wentland 
Signed-off-by: Alex Deucher

drm/amd/display: Implement interface for CRC on CRTC

2018-02-19T19:17:36+00:00

Add interfaces in DC for per CRTC CRC configuration and fetching.
Also implement amdgpu_dm functions to hook onto DRM.

Signed-off-by: Leo (Sunpeng) Li 
Reviewed-by: Tony Cheng 
Reviewed-by: Harry Wentland 
Signed-off-by: Alex Deucher