[Intel-gfx] [PATCH v6 0/6] drm/i915/dp: Support for DP YCbCr4:2:0 outputs

[Gwan-gyeong Mun]

On Gen 11 platform, to enable resolutions like 5K at 120 (or higher) we need
to use DSC (DP 1.4) or YCbCr4:2:0 (DP 1.3 or 1.4) on DP.
In order to support YCbCr4:2:0 on DP we need to program YCBCR 4:2:0
to MSA and VSC SDP.
And Link M/N values are calculated and applied based on the Full Clock
forYCbCr420.
The Bit per Pixel needs to be adjusted for YUV420 mode as it requires only
half of the RGB case.
 - Link M/N values are calculated and applied based on the Full Clock
 - Data M/N values needs to be calculated considering the data is half
   due to subsampling

These patches add a VSC structure for handling Pixel Encoding/Colorimetry
Formats and program YCBCR 4:2:0 to MSA and VSC SDP. And it changes a link
bandwidth computation for DP.

These patches tested on below test environment.
Test Environment: 
 - Tested System: Gen11 platform
 - Monitor: Wasabi Mango UHD430 REAL4K HDMI 2.0 Slim HDR DUAL DP i20
            (This monitor supports HDMI YCbCr 4:2:0)
 - DP to HDMI Adaptor (Dongle) : Club3D CAC-1080 (This dongle supports
                                 DP YCbCr 4:2:0 pass through feature.)
 - To enable DP YCbCr 4:2:0 forcely, test enviromnent uses work arounds
   patches. You can find these on
   https://gitlab.freedesktop.org/elongbug/drm-tip/tree/dp_ycbcr420_work

The idea of a scaling (RGB -> YCbCr4:4:4 -> YCbCr 4:2:0) is to follow the
same approach used in YCbCr 4:2:0 on HDMI.

v2: Addressed Maarten's review comments, fixed minor coding and block comment
style. And reordered a first patch  ("drm/i915/dp: Support DP ports
YUV 4:2:0 output to GEN11") as a last patch.

v3: Addressed Ville's review comments.
Style fixed with few naming.
If lscon is active, it makes not to call intel_dp_ycbcr420_config() to avoid
to clobber of lspcon_ycbcr420_config() routine.
And it move the 420_only check into the intel_dp_ycbcr420_config().
Remove a changing of pipe_bpp on intel_ddi_set_pipe_settings().
Because the pipe is running at the full bpp, keep pipe_bpp as RGB even though
YCbCr 4:2:0 output format is used.
Add a link bandwidth computation for YCbCr4:2:0 output format.

v4: Fix uninitialized return value which is reported by Dan Carpenter.

v5: Addressed reivew comments from Ville.
In order to make codes simple, it adds and uses intel_dp_output_bpp() function.
In order to avoid the extra indentation, it inverts if-clause on
intel_dp_ycbcr420_config().
Remove the error print where no errors print are allowed.

v6:
Link M/N values are calculated and applied based on the Full Clock for
YCbCr420. The Bit per Pixel needs to be adjusted for YUV420 mode as it
requires only half of the RGB case.
 - Link M/N values are calculated and applied based on the Full Clock
 - Data M/N values needs to be calculated considering the data is half due
   to subsampling
Remove a doubling of pixel clock on a dot clock calculator for DP YCbCr 4:2:0.
Rebase and remove a duplicate setting of vsc_sdp.DB17.
Add a setting of dynamic range bit to  vsc_sdp.DB17.
Change Content Type bit to "Graphics" from "Not defined".
Change a dividing of pipe_bpp to muliplying to constant values on a switch-case
statement.
Fix an wrong setting of MSA MISC1 fields for Pixel Encoding/Colorimetry
Format indication. As per DP 1.4a spec Table 2-96 [MSA MISC1 and MISC0
Fields for Pixel Encoding/Colorimetry Format Indication] When MISC1, bit 6,
is Set to 1, a Source device uses a VSC SDP to indicate the Pixel
Encoding/Colorimetry Format. On the wrong version it set a bit 5 of MISC1,
now it set a bit 6 of MISC1.

References: https://patchwork.freedesktop.org/series/56059/

Gwan-gyeong Mun (6):
  drm/i915/dp: Add a config function for YCBCR420 outputs
  drm: Add a VSC structure for handling Pixel Encoding/Colorimetry
    Formats
  drm/i915/dp: Program VSC Header and DB for Pixel Encoding/Colorimetry
    Format
  drm/i915/dp: Add a support of YCBCR 4:2:0 to DP MSA
  drm/i915/dp: Change a link bandwidth computation for DP
  drm/i915/dp: Support DP ports YUV 4:2:0 output to GEN11

 drivers/gpu/drm/i915/i915_reg.h  |   1 +
 drivers/gpu/drm/i915/intel_ddi.c |  12 ++-
 drivers/gpu/drm/i915/intel_dp.c  | 149 ++++++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/intel_drv.h |   2 +
 include/drm/drm_dp_helper.h      |  17 ++++
 5 files changed, 178 insertions(+), 3 deletions(-)

-- 
2.21.0