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

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Add accessor functions for Snps 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 C20, use 6th table if encoder supports DP 2.0 or higher. Otherwise
use 5th table for DP.

For C20, tables 1-4 are not used at all and are most likely to be
zeroed. 5th table is used for any mode below DP 2.0 (exclusive). 6th
table is used for any mode above DP 2.0 (inclusive).

For C10, use 2nd table for external DP if encoder supports any mode
beyond or including HBR2. Use 1st table if external DP encoder supports
anything lower than HBR2. For eDP, use 4th table if encoder supports
HBR3. Otherwise use 3rd table for eDP.

For C10, 1st table is used for external DP with modes below HBR2
(exclusive). 2nd table is used for external DP with modes higher than
HBR2 (inclusive). 3rd table is used for eDP with modes lower than HBR3
(exclusive). 4th table is used for eDP with modes higher than HBR3
(inclusive).

Indices for other tables have not yet been observed to be used as of
now.

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.

v11->v12
- don't set vspeo->num_entries per PHY
- don't refer to 1st table as fallback for non-DP for C10 (Sashiko)

v10->v11
- remove no-longer-relevant check for NULL devdata (Jani)
- initialize local variables at declaration block (Jani)
- branch with 'else` instead of initializing twice (Jani)
- use blank line before 'return` (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
- init vspeo before using it
- deconstify intel_ddi_buf_trans_entry

v7->v8
- remove comments (Suraj)
- add check for LT (Suraj)

v6->v7
- handle VS/PE-O's VBT details in intel_bios_* functions (Jani)
- remove vspeo's cast to (void *) (Jani)
- check devdata->vspeo if VS/PE-O was requested
- 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)
- inline mtl_{c10,c20}_get_vspeo_buf_trans()
- remove temporarily LT

v4->v5
- blend index computation with table parsing
- remove enums entirely
- change funcs prefix from snps_ to mtl_ (Suraj)
- add spaces around operators (Suraj)
- remove spaces after type casting (Suraj)
- remove INTEL_DISPLAY_STATE_WARN (Suraj)

v3->v4
- stick to solely changing VBT data into current structures (Jani)
- move iterator declaration to declaration block (Suraj)

v2->v3
- remove unnecessary braces from if block (Suraj)
- return -EINVAL instead of -1 (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/20260904123148.2165596-7-michal.grzelak@intel.com

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This commit is contained in:

Michał Grzelak 2026-09-04 14:31:46 +02:00 • committed by Suraj Kandpal

parent e084812de9

commit e8fe5008ae

3 changed files with 133 additions and 2 deletions

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91

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

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7

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

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37

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

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