[RFC v4 00/17] drm/display/dp_mst: Drop Radeon MST support, make MST atomic-only

[Lyude Paul]

Actually, talked with airlied and they suggested at this point I should just
go ahead and push. So, pushed! Have fun getting nice DSC support everyone :)

On Tue, 2022-08-23 at 13:26 -0400, Lyude Paul wrote:
> Would anyone have any issues if I merged this today? The whole series is
> acked, but I'm not sure if we would like to wait for R-b's?
> 
> 
> On Wed, 2022-08-17 at 15:38 -0400, Lyude Paul wrote:
> > For quite a while we've been carrying around a lot of legacy modesetting
> > code in the MST helpers that has been rather annoying to keep around,
> > and very often gets in the way of trying to implement additional
> > functionality in MST such as fallback link rate retraining, dynamic BPC
> > management and DSC support, etc. because of the fact that we can't rely
> > on atomic for everything.
> > 
> > Luckily, we only actually have one user of the legacy MST code in the
> > kernel - radeon. Originally I was thinking of trying to maintain this
> > code and keep it around in some form, but I'm pretty unconvinced anyone
> > is actually using this. My reasoning for that is because I've seen
> > nearly no issues regarding MST on radeon for quite a while now - despite
> > the fact my local testing seems to indicate it's quite broken. This
> > isn't too surprising either, as MST support in radeon.ko is gated behind
> > a module parameter that isn't enabled by default. This isn't to say I
> > wouldn't be open to alternative suggestions, but I'd rather not be the
> > one to have to spend time on that if at all possible! Plus, I already
> > floated the idea of dropping this code by AMD folks a few times and
> > didn't get much resistance.
> > 
> > As well, this series has some basic refactoring that I did along the way
> > and some bugs I had to fix in order to get my atomic-only MST code
> > working. Most of this is pretty straight forward and simply renaming
> > things to more closely match the DisplayPort specification, as I think
> > this will also make maintaining this code a lot easier in the long run
> > (I've gotten myself confused way too many times because of this).
> > 
> > So far I've tested this on all three MST drivers: amdgpu, i915 and
> > nouveau, along with making sure that removing the radeon MST code
> > doesn't break anything else. The one thing I very much could use help
> > with regarding testing though is making sure that this works with
> > amdgpu's DSC support on MST.
> > 
> > So, with this we should be using the atomic state as much as possible
> > with MST modesetting, hooray!
> > 
> > V4:
> > * Get rid of fix that Wayne pointed out isn't needed
> > 
> > Cc: Wayne Lin <Wayne.Lin at amd.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Cc: Fangzhi Zuo <Jerry.Zuo at amd.com>
> > Cc: Jani Nikula <jani.nikula at intel.com>
> > Cc: Imre Deak <imre.deak at intel.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Cc: Sean Paul <sean at poorly.run>
> > 
> > Lyude Paul (17):
> >   drm/amdgpu/dc/mst: Rename dp_mst_stream_allocation(_table)
> >   drm/amdgpu/dm/mst: Rename get_payload_table()
> >   drm/display/dp_mst: Rename drm_dp_mst_vcpi_allocation
> >   drm/display/dp_mst: Call them time slots, not VCPI slots
> >   drm/display/dp_mst: Fix confusing docs for
> >     drm_dp_atomic_release_time_slots()
> >   drm/display/dp_mst: Add some missing kdocs for atomic MST structs
> >   drm/display/dp_mst: Add helper for finding payloads in atomic MST
> >     state
> >   drm/display/dp_mst: Add nonblocking helpers for DP MST
> >   drm/display/dp_mst: Don't open code modeset checks for releasing time
> >     slots
> >   drm/display/dp_mst: Fix modeset tracking in
> >     drm_dp_atomic_release_vcpi_slots()
> >   drm/nouveau/kms: Cache DP encoders in nouveau_connector
> >   drm/nouveau/kms: Pull mst state in for all modesets
> >   drm/display/dp_mst: Add helpers for serializing SST <-> MST
> >     transitions
> >   drm/display/dp_mst: Drop all ports from topology on CSNs before
> >     queueing link address work
> >   drm/display/dp_mst: Maintain time slot allocations when deleting
> >     payloads
> >   drm/radeon: Drop legacy MST support
> >   drm/display/dp_mst: Move all payload info into the atomic state
> > 
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   68 +-
> >  .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |  108 +-
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   |  125 +-
> >  drivers/gpu/drm/amd/display/dc/core/dc_link.c |   10 +-
> >  drivers/gpu/drm/amd/display/dc/dm_helpers.h   |    4 +-
> >  .../amd/display/include/link_service_types.h  |   14 +-
> >  drivers/gpu/drm/display/drm_dp_mst_topology.c | 1137 ++++++++---------
> >  drivers/gpu/drm/i915/display/intel_display.c  |    6 +
> >  drivers/gpu/drm/i915/display/intel_dp.c       |    9 +
> >  drivers/gpu/drm/i915/display/intel_dp_mst.c   |   91 +-
> >  drivers/gpu/drm/i915/display/intel_hdcp.c     |   24 +-
> >  drivers/gpu/drm/nouveau/dispnv50/disp.c       |  197 ++-
> >  drivers/gpu/drm/nouveau/dispnv50/disp.h       |    2 +
> >  drivers/gpu/drm/nouveau/nouveau_connector.c   |   18 +-
> >  drivers/gpu/drm/nouveau/nouveau_connector.h   |    3 +
> >  drivers/gpu/drm/radeon/Makefile               |    2 +-
> >  drivers/gpu/drm/radeon/atombios_crtc.c        |   11 +-
> >  drivers/gpu/drm/radeon/atombios_encoders.c    |   59 -
> >  drivers/gpu/drm/radeon/radeon_atombios.c      |    2 -
> >  drivers/gpu/drm/radeon/radeon_connectors.c    |   61 +-
> >  drivers/gpu/drm/radeon/radeon_device.c        |    1 -
> >  drivers/gpu/drm/radeon/radeon_dp_mst.c        |  778 -----------
> >  drivers/gpu/drm/radeon/radeon_drv.c           |    4 -
> >  drivers/gpu/drm/radeon/radeon_encoders.c      |   14 +-
> >  drivers/gpu/drm/radeon/radeon_irq_kms.c       |   10 +-
> >  drivers/gpu/drm/radeon/radeon_mode.h          |   40 -
> >  include/drm/display/drm_dp_mst_helper.h       |  234 ++--
> >  27 files changed, 955 insertions(+), 2077 deletions(-)
> >  delete mode 100644 drivers/gpu/drm/radeon/radeon_dp_mst.c
> > 
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat