kernel/linux.git/drivers/gpu/drm/msm/dp/dp_ctrl.c, branch v6.18.22

drm/msm/dp: Avoid division by zero in msm_dp_ctrl_config_msa()

2026-02-26T22:59:13+00:00

[ Upstream commit f185076da44c774241a16a82a7773ece3c1c607b ] An (admittedly problematic) optimization change in LLVM 20 [1] turns known division by zero into the equivalent of __builtin_unreachable(), which invokes undefined behavior if it is encountered in a control flow graph, destroying code generation. When compile testing for x86_64, objtool flags an instance of this optimization triggering in msm_dp_ctrl_config_msa(), inlined into msm_dp_ctrl_on_stream(): drivers/gpu/drm/msm/msm.o: warning: objtool: msm_dp_ctrl_on_stream(): unexpected end of section .text.msm_dp_ctrl_on_stream The zero division happens if the else branch in the first if statement in msm_dp_ctrl_config_msa() is taken because pixel_div is initialized to zero and it is not possible for LLVM to eliminate the else branch since rate is still not known after inlining into msm_dp_ctrl_on_stream(). Transform the if statements into a switch statement with a default case with the existing error print and an early return to avoid the invalid division. Add a comment to note this helps the compiler, even though the case is known to be unreachable. With this, pixel_dev's default zero initialization can be dropped, as it is dead with this change. Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support") Link: https://github.com/llvm/llvm-project/commit/37932643abab699e8bb1def08b7eb4eae7ff1448 [1] Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202601081959.9UVJEOfP-lkp@intel.com/ Suggested-by: Konrad Dybcio Signed-off-by: Nathan Chancellor Reviewed-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/698355/ Link: https://lore.kernel.org/r/20260113-drm-msm-dp_ctrl-avoid-zero-div-v2-1-f1aa67bf6e8e@kernel.org Signed-off-by: Dmitry Baryshkov Signed-off-by: Sasha Levin

drm/msm/dp: drop the msm_dp_catalog module

2025-07-04T13:35:19+00:00

Now as the msm_dp_catalog module became nearly empty, drop it, accessing registers directly from the corresponding submodules. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654332/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-11-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: move interrupt handling to dp_ctrl

2025-07-04T13:35:19+00:00

It makes it easier to keep all interrupts-related code in dp_ctrl submodule. Move all functions to dp_ctrl.c. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654330/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-10-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: move more AUX functions to dp_aux.c

2025-07-04T13:35:18+00:00

Move several misnamed functions accessing AUX bus to dp_aux.c, further cleaning up dp_catalog submodule. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654333/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-9-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: move/inline ctrl register functions

2025-07-04T13:35:18+00:00

Move CTRL-related functions to dp_ctrl.c, inlining one line wrappers during this process. The enable/disable functions have been split to the enable/disable or enter/exit pairs. The IRQ and HPD related functions are left in dp_catalog.c, pending later cleanup. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654328/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-8-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: move/inline panel related functions

2025-07-04T13:35:18+00:00

Move panel-related functions to dp_panel.c, following up the cleanup done by the rest of the submodules. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654321/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-6-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: split MMSS_DP_DSC_DTO register write to a separate function

2025-07-04T13:35:18+00:00

It's the dp_panel's duty to clear the MMSS_DP_DSC_DTO register. Once DP driver gets DSC support, it will handle that register in other places too. Split a call to write 0x0 to that register to a separate function. Reviewed-by: Stephen Boyd Tested-by: Stephen Boyd # sc7180-trogdor Signed-off-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/654314/ Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-1-2f0ec3ec000d@oss.qualcomm.com

drm/msm/dp: Introduce link training per-segment for LTTPRs

2025-05-12T16:18:49+00:00

DisplayPort requires per-segment link training when LTTPR are switched to non-transparent mode, starting with LTTPR closest to the source. Only when each segment is trained individually, source can link train to sink. Implement per-segment link traning when LTTPR(s) are detected, to support external docking stations. On higher level, changes are: * Pass phy being trained down to all required helpers * Run CR, EQ link training per phy * Set voltage swing, pre-emphasis levels per phy Since at least some LTTPRs (eg. Parade PS8830) do not correctly report voltage-swing, pre-emphasis level 3 support, always assume level 3 is supported. This is permitted under DP 2.1(a) section 3.6.7.2 stating that LTTPR shall set its transmitter levels as close as possible to those requested by the DPTX, if the DPTX sets the voltage swing or pre-emphasis to a level that the LTTPR does not support. It shall be noted that LTTPR’s level choosing is implementation-specific. This ensures successful link training both when connected directly to the monitor (single LTTPR onboard most X1E laptops) and via the docking station (at least two LTTPRs). Fixes: 72d0af4accd9 ("drm/msm/dp: Add support for LTTPR handling") Tested-by: Jessica Zhang # SA8775P Tested-by: Johan Hovold Tested-by: Rob Clark Tested-by: Stefan Schmidt Signed-off-by: Aleksandrs Vinarskis Reviewed-by: Abel Vesa Reviewed-by: Abhinav Kumar Reviewed-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/652305/ Link: https://lore.kernel.org/r/20250507230113.14270-5-alex.vinarskis@gmail.com Signed-off-by: Dmitry Baryshkov

Merge drm/drm-next into drm-misc-next

2025-04-07T12:35:48+00:00

Backmerging to get v6.15-rc1 into drm-misc-next. Also fixes a build issue when enabling CONFIG_DRM_SCHED_KUNIT_TEST. Signed-off-by: Thomas Zimmermann

drm/display: dp: change drm_dp_dpcd_read_link_status() return value

2025-03-25T14:20:38+00:00

drm_dp_dpcd_read_link_status() follows the "return error code or number of bytes read" protocol, with the code returning less bytes than requested in case of some errors. However most of the drivers interpreted that as "return error code in case of any error". Switch drm_dp_dpcd_read_link_status() to drm_dp_dpcd_read_data() and make it follow that protocol too. Acked-by: Jani Nikula Reviewed-by: Lyude Paul Signed-off-by: Dmitry Baryshkov Link: https://lore.kernel.org/r/20250324-drm-rework-dpcd-access-v4-2-e80ff89593df@oss.qualcomm.com Signed-off-by: Dmitry Baryshkov