[SRU][OEM-5.14/J][PATCH 0/4] Fix DP tunneling issues on AMD Rembrandt

Stefan Bader stefan.bader at canonical.com
Mon Aug 1 08:43:09 UTC 2022

On 29.07.22 20:56, Mario Limonciello wrote:
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1983143
> When a Thunderbolt monitor or Thunderbolt dock are connected to a USB4
> port on AMD Yellow Carp (Rembrandt) a software connection manager works
> with the hardware to initialize tunnels.
> One of those tunnels is for DP (display port). It was observed that
> on both the OEM-5.14 as well as Jammy-5.15 kernel that DP tunneling
> specifically when connecting to a Thunderbolt monitor fails.
> This circumstance does not happen on OEM-5.17 or mainline kernels.
> This is due to a backport error on the USB4 patch series that went
> into OEM-5.14 and moved forward to Jammy-5.15.  Patch 1/4 in this
> series corrects that error as minimally as possible as a SAUCE patch.
> It was also observed that DP tunneling is not working for Thunderbolt
> monitor connected at boot, but this is a different root cause.
> The "Pre-OS" connection manager creates DP tunnels that are expected
> to be re-used by the OS connection manager. The remaining patches in
> this series enable this flow.
> For this whole flow to work an updated AMDGPU DMCUB firmware is also
> needed.  This is already in process as part of:
> https://bugs.launchpad.net/ubuntu/+source/linux-firmware/+bug/1981922
> Mario Limonciello (1):
>    UBUNTU: SAUCE: drm/amd: Fix DP Tunneling with Thunderbolt monitors

Hi Mario,

while your patch contains good reasoning for why it is a non-upstream patch, the 
other SAUCE patch is not that clear. From the s-o-b reference it sounds like it 
might go upstream which makes one wonder why not taking it from there.

> Meenakshikumar Somasundaram (1):
>    drm/amd/display: Fix for dmub outbox notification enable
> Sanjay R Mehta (1):
>    UBUNTU: SAUCE: thunderbolt: Add DP out resource when DP tunnel is
>      discovered.
> Stylon Wang (1):
>    drm/amd/display: Fix new dmub notification enabling in DM

That one ^ I would rather declare a backport and annotate with short hints about 
what was worked around. Like "use <name> instead of <other name>". Mentioning 
which changes are missing is nice in addition but for glancing over submissions 
it is much simpler to get told what to watch out for.

To be clear I am not asking to re-submit. If we can clarify things we can make 
the adjustments when we apply things.


>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 24 +++++--
>   drivers/gpu/drm/amd/display/dc/core/dc.c      | 66 +++++++++++++++++--
>   drivers/gpu/drm/amd/display/dc/dc.h           |  3 +
>   .../gpu/drm/amd/display/dc/dce/dmub_outbox.c  | 25 +++----
>   .../gpu/drm/amd/display/dc/dce/dmub_outbox.h  |  4 +-
>   .../amd/display/dc/dcn10/dcn10_hw_sequencer.c |  4 --
>   .../drm/amd/display/dc/dcn20/dcn20_hwseq.c    |  4 ++
>   .../drm/amd/display/dc/dcn31/dcn31_hwseq.c    |  2 +-
>   drivers/thunderbolt/tb.c                      | 15 +++++
>   drivers/thunderbolt/tb.h                      |  1 +
>   drivers/thunderbolt/tunnel.c                  |  2 +
>   11 files changed, 121 insertions(+), 29 deletions(-)

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