linux.git/drivers/gpu/drm/amd/display/dc/link/protocols, branch master

drm/amd/display: fix division by zero in get_estimated_bw()

2026-09-02T20:57:38+00:00

get_estimated_bw() divides by link->dpia_bw_alloc_config.bw_granularity,
which is zeroed by reset_bw_alloc_struct() and only populated once
DP_TUNNELING_BW_ALLOC_CAP_CHANGED has been handled.

link_dp_dpia_handle_bw_alloc_status(), the DPCD interrupt handler,
calls get_estimated_bw() whenever DP_TUNNELING_ESTIMATED_BW_CHANGED
is set, independently of whether DP_TUNNELING_BW_ALLOC_CAP_CHANGED
has ever fired for that link. A connected USB4/DPIA tunneling device
that reports an estimated-bandwidth change before ever reporting a
capability change drives a division by zero in this IRQ path.

link_dpia_send_bw_alloc_request() already guards the same
bw_granularity division; add the identical guard here rather than
introducing a new pattern.

Fixes: 8e5cfe547bf3 ("drm/amd/display: upstream link_dp_dpia_bw.c")
Reviewed-by: Alex Hung 
Assisted-by: gkh_clanker_t1000
Signed-off-by: Hari Mishal 
Signed-off-by: Alex Deucher 
(cherry picked from commit f2a961457c33dc34223aad5c9e8971de34a4eed3)
Cc: stable@vger.kernel.org

drm/amd/display: Ensure dtbclk is enabled

2026-08-06T13:58:19+00:00

[why]
ensure dtbclk is enabled before hdmistreamclk_en

pmfw could stop dtbclk on idle.
driver needs to ensure dtbclk enabled is enabled before hdmistreamclk_en
also disable debounce timer on dcn42.

Reviewed-by: Chris Park 
Reviewed-by: Leo Chen 
Signed-off-by: Charlene Liu 
Signed-off-by: Roman Li 
Tested-by: Dan Wheeler 
Signed-off-by: Alex Deucher

drm/amd/display: Enable DCN6 sources compilation

2026-08-06T13:53:32+00:00

- Add hooks in various entry points to perform hw/sw init for DCN6 asic
- Add dependent changes needed to enable DCN6 asic
- Update the Makefiles so that DCN6 related newly added sources are compiled

Signed-off-by: Aurabindo Pillai 
Signed-off-by: Roman Li 
Reviewed-by: Ivan Lipski 
Tested-by: Dan Wheeler 
Signed-off-by: Alex Deucher

drm/amd/display: Fix force FRL rate debug setting

2026-07-28T22:58:15+00:00

[Why & How]
- force FRL rate debug bit was not correctly forcing requested FRL rate

Reviewed-by: Chris Park 
Signed-off-by: Relja Vojvodic 
Signed-off-by: Fangzhi Zuo 
Tested-by: Dan Wheeler 
Signed-off-by: Alex Deucher

drm/amd/display: Fix DP LT failure logging

2026-07-28T22:32:25+00:00

[Why/How]
The final DP LT failure meant to be logged as DC warning is skipped due
to a break statement above. Move logging up to make sure we don't miss
LT fail events.

Reviewed-by: George Shen 
Signed-off-by: Ilya Bakoulin 
Signed-off-by: Wayne Lin 
Tested-by: Dan Wheeler 
Signed-off-by: Alex Deucher

drm/amd/display: remove duplicate link_dp_panel_replay.h include

2026-07-15T13:15:43+00:00

link_dp_irq_handler.c includes "link_dp_panel_replay.h" twice. Drop the
redundant second include; this is a non-functional cleanup flagged by
scripts/checkincludes.pl.

Fixes: 1e5cd4adfc54 ("drm/amd/display: move panel replay out from edp")
Signed-off-by: Anas Khan 
Reviewed-by: George Zhang 
Signed-off-by: Alex Deucher

drm/amd/display: Fix VABC Init and OLED Support

2026-07-15T13:15:39+00:00

[Why]
TCONs supporting VESA AUX Backlight does not always
support VESA Smooth Brightness. Driver software
needs to implement smooth brightness by periodically
updating the brightness by small steps. Driver
implementation is completed and verified on LCD
panels but solution is missing for OLED panels.

[How]
Updated driver to include smooth brightness for
OLED panels using VESA Aux Backlight.
Revert original workaround for VABC on oled issue,
as it is no longer needed.
Add VABC backlight Initialization sequence from
driver side.
Add fix to remove conflict between FW and driver
backlight programming for future ASIC.
Enable VABC for all future asic revisions.

Reviewed-by: Anthony Koo 
Reviewed-by: Dillon Varone 
Signed-off-by: Iswara Nagulendran 
Signed-off-by: George Zhang 
Signed-off-by: Alex Deucher

drm/amd/display: Add dp_skip_rbr flag for NUTMEG

2026-07-15T13:15:37+00:00

No functional changes. Just clean up a conceptual mismatch.

Based on feedback on the NUTMEG code in DC, the
preferred_link_setting is meant to force the DP link to a
specific setting, meaning both the link rate and lane count
should be locked to an exact value. What NUTMEG needs is
a lower bound on the link rate, which is not the same concept.

Implement this as a HW workaround flag instead.

Suggested-by: Wenjing Liu 
Signed-off-by: Timur Kristóf 
Signed-off-by: Alex Deucher

drm/amd/display: Fix preferred link rate for NUTMEG

2026-07-15T13:15:37+00:00

When there is a preferred link rate setting, it needs to be
applied to both the current and initial link rate.
This was regressed by a "coding style" fix, which caused
the current link rate to not respect the preferred value.

This commit restores the functionality of NUTMEG,
the DP bridge encoder found on old APUs such as Kaveri.

Fixes: a62346043a89 ("drm/amd/display: Fix coding style issue")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5465
Cc: Chuanyu Tseng 
Reviewed-by: Fangzhi Zuo 
Signed-off-by: Timur Kristóf 
Signed-off-by: Alex Deucher

drm/amd/display: Replace repeated no-native-i2c checks with force_i2c_over_aux field

2026-07-01T15:31:10+00:00

[Why]
The compound condition checking dp_connector_no_native_i2c
and no_ddc_pin was duplicated across many files, obscuring
intent at every call site.

[How]
Add bool force_i2c_over_aux to struct dc_link, initialized
once during link creation. Add link_get_ddc_aux_inst()
helper to select the correct aux instance. Wire into
link_service via construct_link_service_ddc(). Replace all
duplicated condition checks and aux instance selection
blocks with the new field and helper. No functional change.

Reviewed-by: Nevenko Stupar 
Signed-off-by: Wenjing Liu 
Signed-off-by: George Zhang 
Signed-off-by: Alex Deucher