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drm/amd/display: Unify CalculateFlipSchedule Logic

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[Why]
CalculateFlipSchedule has slightly different calculations depending on
if it was called by mode support or mode programming.

Mode support calculates the lower bound of the required bandwidth for
immediate flips.
This takes into the account of the register limits to ensure it is still
programmable.

Mode programming uses the required bandwidth for immediate flips on a
per-plane basis
to calculate the number of dst_y lines needed to achieve this bandwidth.

Usually the immediate flip bandwidth per plane determined by mode
programming is above the lower bound
calculated by mode support.
However, mode programming can fail if that isn't the case since a bandwidth
lower than the lower bound will
end up exceeding the register limit used by hardware.
e.g. The proportion of a single plane's flip bandwidth w.r.t to the total
bandwidth available for all planes
can result in one of the planes having a lower BW than the lower bound
calculated in mode support

[How]
Update function to always use the use_lb_flip_bw path.
Add calculations for dst_y_per_vm/row_flip lines.
Consolidate calculation of lb_flip_bw by having it consider register
limits:
Instead of doing two steps of:
1. Taking the max of the bandwidths without considering register limits.
2. Taking the max of itself with the bandwidths with register limits
accounted for.
Do it in one step as it is easy to miss either step 1 or 2.

Also add some local variables for intermediate values and remove no longer
referenced inputs to improve readability.

Also increase DCN401 max_flip_time_lines by 2 lines to ensure previously
supported configs remain supported as worst-case
bandwidth can increase compared to before.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Austin Zheng <Austin.Zheng@amd.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Austin Zheng 2026-07-31 10:24:45 -04:00 • committed by Alex Deucher
commit 1e719006b6
3 changed files with 66 additions and 103 deletions
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