Re: [PATCH v4 00/39] drm/msm/dp: Add MST support for MSM chipsets

Dmitry Baryshkov
2026-04-10T13:53:21Z

On Fri, Apr 10, 2026 at 05:33:35PM +0800, Yongxing Mou wrote:
> Add support for Multi-stream transport for MSM chipsets that allow
> a single instance of DP controller to send multiple streams.
>
> This series has been validated on sa8775p ride platform using multiple
> MST dongles and also daisy chain method on both DP0 and DP1 upto 1080P.
>
> With 4x4K monitors, due to lack of layer mixers that combination will not
> work but this can be supported as well after some rework on the DPU side.
>
> In addition, SST was re-validated with all these changes to ensure there
> were no regressions.
>
> This patch series was made on top of:
>
> [1] : https://patchwork.freedesktop.org/series/151522/ (v5 to fix up HPD)
>
> Overall, the patch series has been organized in the following way:
>
> 1) First set are a couple of fixes made while debugging MST but applicable
> to SST as well so go ahead of everything else
> 2) Prepare the DP driver to get ready to handle multiple streams. This is the bulk
> of the work as current DP driver design had to be adjusted to make this happen.
> 3) Finally, new files to handle MST related operations
>
> Note:
> Validation for this series has so far been done on the latest linux-next
> on LeMans, covering both FB console and Weston.
>
> Broader validation, including additional Type-C DP use cases, is still
> in progress and may lead to some follow-up adjustments in the next
> revision. I wanted to post the current version first to collect early
> feedback on the overall approach.

It's fine to post the current state, thank you. But I'd definitely want
it to be regularly tested with the USB-C attachment.

>
> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
> ---
> Changes in v4:
> - Fixed most comments from V3.
> - Rebase onto HPD refactor V5.
> - Fixed casing/formatting issues, for example: “mst”.
> - Drop .mode_set() and set_mode in .atomic_enable().
> - Rewrite commit messages that are unclear.
> - Use the same API for MST link and SST link writes.
> - Use the new drm_dp_dpcd_read_byte() / drm_dp_dpcd_write_byte() interfaces.
> - Remove some unnecessary payload fields from the MST bridge.
> - Remove some defensive NULL pointer checks.
> - Reworked the patch order to make the series easier to follow.
> - Add support for more platforms.
> - Link to v3: https://lore.kernel.org/r/20250825-msm-dp-mst-v3-0-01faacfcdedd@oss.qualcomm.com
>
> Changes in v3: Fixed review comments from Dmitry
> - Fixed lots of comments from series V1/V2.
> - Rebased onto next-20250808.
> - Rebased onto Jessica's HPD-refactor branch.
> - Fixed formatting issues in commit messages under changes.
> - Removed unnecessary one-line wrappers.
> - Relocated MST-related .atomic_check() calls to their appropriate positions.
> - Removed the logic related to slot checking in .mode_valid().
> - Link to v2: https://lore.kernel.org/r/20250609-msm-dp-mst-v2-0-a54d8902a23d@quicinc.com
>
> Changes in v2: Fixed review comments from Dmitry
> - Rebase on top of next-20250606
> - Add all 4 streams pixel clks support and MST2/MST3 Link clk support
> - Address the formatting issues mentioned in the review comments
> - Drop the cache of msm_dp_panel->drm_edid cached
> - Remove the one-line wrapper funtion and redundant conditional check
> - Fixed the commit messgae descriptions of some patches
> - Reordered the patches and renamed some functions and variables
> - Link to v1: https://lore.kernel.org/all/20241205-dp_mst-v1-0-f
> 8618d42a99a@quicinc.com/
>
> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>
> ---
> Abhinav Kumar (26):
> drm/msm/dp: break up dp_display_enable into two parts
> drm/msm/dp: re-arrange dp_display_disable() into functional parts
> drm/msm/dp: allow dp_ctrl stream APIs to use any panel passed to it
> drm/msm/dp: split dp_ctrl_off() into stream and link parts
> drm/msm/dp: make bridge helpers use dp_display to allow re-use
> drm/msm/dp: separate dp_display_prepare() into its own API
> drm/msm/dp: introduce stream_id for each DP panel
> drm/msm/dp: introduce max_streams for DP controller MST support
> drm/msm/dp: Add support for programming p1/p2/p3 register blocks
> drm/msm/dp: use stream_id to change offsets in dp_catalog
> drm/msm/dp: add support to send ACT packets for MST
> drm/msm/dp: Add support to enable MST in mainlink control
> drm/msm/dp: no need to update tu calculation for mst
> drm/msm/dp: Add support for MST channel slot allocation
> drm/msm/dp: Add support for sending VCPF packets in DP controller
> drm/msm/dp: Always program MST_FIFO_CONSTANT_FILL for MST use cases
> drm/msm/dp: abstract out the dp_display stream helpers to accept a panel
> drm/msm/dp: replace power_on with active_stream_cnt for dp_display
> drm/msm/dp: Mark the SST bridge disconnected when mst is active
> drm/msm/dp: add an API to initialize MST on sink side
> drm/msm/dp: add dp_display_get_panel() to initialize DP panel
> drm/msm/dp: initialize dp_mst module for each DP MST controller
> drm/msm/dp: add dp_mst_drm to manage DP MST bridge operations
> drm/msm/dp: add connector abstraction for DP MST
> drm/msm/dp: add HPD callback for dp MST
> drm/msm/dpu: use msm_dp_get_mst_intf_id() to get the intf id
>
> Yongxing Mou (13):
> drm/msm/dp: remove cached drm_edid from panel
> drm/msm/dp: drop deprecated .mode_set() and use .atomic_enable
> drm/msm/dp: splite msm_dp_ctrl_config_ctrl() into link parts and stream parts
> drm/msm/dp: extract MISC1_MISC0 configuration into a separate function
> drm/msm/dp: split link setup from source params
> drm/msm/dp: move the pixel clock control to its own API
> drm/msm/dp: Add catalog support for 3rd/4th stream MST
> drm/msm/dp: simplify link and clock disable sequence
> drm/msm/dp: pass panel to display enable/disable helpers
> drm/msm/dp: add prepared to manage link-level operations
> drm/msm/dpu: initialize encoders per stream for DP MST
> drm/msm/dp: wire MST helpers into atomic check and commit paths
> drm/msm/dp: Add MST stream support for supported DP controllers
>
> drivers/gpu/drm/msm/Makefile | 3 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 20 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 2 +
> drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 30 +-
> drivers/gpu/drm/msm/dp/dp_audio.c | 2 +-
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 822 +++++++++++++++++++++-------
> drivers/gpu/drm/msm/dp/dp_ctrl.h | 24 +-
> drivers/gpu/drm/msm/dp/dp_display.c | 598 ++++++++++++++------
> drivers/gpu/drm/msm/dp/dp_display.h | 31 +-
> drivers/gpu/drm/msm/dp/dp_drm.c | 43 +-
> drivers/gpu/drm/msm/dp/dp_drm.h | 12 -
> drivers/gpu/drm/msm/dp/dp_mst_drm.c | 795 +++++++++++++++++++++++++++
> drivers/gpu/drm/msm/dp/dp_mst_drm.h | 14 +
> drivers/gpu/drm/msm/dp/dp_panel.c | 315 +++++++----
> drivers/gpu/drm/msm/dp/dp_panel.h | 32 +-
> drivers/gpu/drm/msm/dp/dp_reg.h | 48 +-
> drivers/gpu/drm/msm/msm_atomic.c | 9 +-
> drivers/gpu/drm/msm/msm_drv.h | 18 +
> drivers/gpu/drm/msm/msm_kms.c | 2 +
> 19 files changed, 2300 insertions(+), 520 deletions(-)
> ---
> base-commit: 3ef088b0c5772a6f75634e54aa34f5fc0a2c041c
> change-id: 20260410-msm-dp-mst-35130b6e8b84
> prerequisite-message-id: <20260305-mdss_catalog-v5-0-06678ac39ac7@oss.qualcomm.com>
> prerequisite-patch-id: 8b3f7f40025e7a10c4646435e9cfec4f9e275871
> prerequisite-patch-id: 547db98962f20218380e966b976aede824ff8433
> prerequisite-message-id: <20260314-hpd-refactor-v5-0-0c8450737d64@oss.qualcomm.com>
> prerequisite-patch-id: 1867c344ef6ead1034523ba65d2640f9ad0606cd
> prerequisite-patch-id: a58ebaf429385c622869c83e83ce7ffdfe9ea27e
> prerequisite-patch-id: d0f570e57559248ba6ca733f96fdb02af29f3055
> prerequisite-patch-id: 44d390f5319068ad534c4be698dd8dba99c0bfd1
> prerequisite-patch-id: 85438690573583cf62065f43531dbb4e221e9dd0
> prerequisite-patch-id: b37db0f0b10f16ed45ab056aa87f2275bb02df94
> prerequisite-patch-id: dcccd204ee8a979328719d41334453474bcfdf98
> prerequisite-patch-id: db07c3aa80a597c91ae2329bc677bfd72b63716a
> prerequisite-patch-id: 9778cc1ab60a0870a74d58ff220bb01011fdf1c0
> prerequisite-patch-id: 95692a605647e51bdaf8d5b2e61635a6978121f0
>
> Best regards,
> --
> Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>

--
With best wishes
Dmitry