drm/i915: override Combo's VS/PE when requested

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Add accessor function for Combo to read requested table from VBT #57.
Parse the requested table and transform data into port's buffer.

Actual data is fully stored in the lowest byte although each entry is 4
bytes wide. Thus convert u32 into u8 and store the data.

For EHL, in cases when eDP encoder uses low vswing, choose 3rd table if
encoder supports HBR3. Otherwise use 2nd table for eDP using low vswing.

In cases when eDP encoder does not use low vswing, choose 2nd table if
encoder supports mode higher or including HBR2. Otherwise use 1st table
for eDP not using low vswing.

For external DP follow same path and use same indices as in eDP without
low vswing case.

For JSL, always use 1st table for external DP. For eDPs not using low
vswing use 1st table as well.

In cases when eDP encoder uses low vswing, choose 1st table if encoder
supports HBR3. When encoder supports HBR2 choose 3rd table. When
encoder supports modes lower than HBR2 choose 2nd table.

There are no changes to intel_ddi_dp_level() since selection of correct
row of intel_ddi_buf_trans_entry is same as when no override request has
been done.

Looking from other OSes, in case when encoder does not support DP we
could theoretically use 1st table. However, as of now, use default
tables.

v11->v12
- don't set vspeo->num_entries per PHY/platform
- check for low vswing eDP for EHL (Sashiko)
- reverse order of indices for JSL (Sashiko)

v10->v11
- initialize local variables at declaration block (Jani)
- branch with 'else` instead of initializing twice (Jani)

v9->v10
- call dedicated VS/PE-O vfunc
- drop deconstifying default tables (Suraj, Jani)
- cache `entries` into const field after data is overwritten (Jani)

v8->v9
- deconstify intel_ddi_buf_trans_entry

v6->v7
- handle VS/PE-O's VBT details in intel_bios_* functions (Jani)
- remove vspeo's cast to (void *) (Jani)
- call encoder->get_buf_trans() once (Jani)
- return NULL from intel_bios_get_* when using default (Jani)
- validate VS/PE-O in intel_bios.c (Jani)
- check devdata->vspeo if VS/PE-O was requested
- inline {jsl,ehl}_combo_get_vspeo_buf_trans()
- remove temporarily LT

v4->v5
- blend index computation with table parsing
- remove enums entirely
- add spaces around operators (Suraj)
- remove spaces after type casting (Suraj)
- remove INTEL_DISPLAY_STATE_WARN (Suraj)

Signed-off-by: Michał Grzelak <michal.grzelak@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260907122742.2512901-1-michal.grzelak@intel.com

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This commit is contained in:

Michał Grzelak 2026-09-07 14:27:42 +02:00 • committed by Suraj Kandpal

parent e8fe5008ae

commit 7fdf86e530

3 changed files with 140 additions and 4 deletions

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93

drivers/gpu/drm/i915/display/intel_bios.c

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6

drivers/gpu/drm/i915/display/intel_bios.h

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45

drivers/gpu/drm/i915/display/intel_ddi_buf_trans.c

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