drm/i915/vrr: Clamp guardband as per hardware and timing constraints

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The maximum guardband value is constrained by two factors:
- The actual vblank length minus set context latency (SCL)
- The hardware register field width:
  - 8 bits for ICL/TGL (VRR_CTL_PIPELINE_FULL_MASK -> max 255)
  - 16 bits for ADL+ (XELPD_VRR_CTL_VRR_GUARDBAND_MASK -> max 65535)

Remove the #FIXME and clamp the guardband to the maximum allowed value.

v2:
- Use REG_FIELD_MAX(). (Ville)
- Separate out functions for intel_vrr_max_guardband(),
  intel_vrr_max_vblank_guardband(). (Ville)

v3:
- Fix Typo: Add the missing adjusted_mode->crtc_vdisplay in guardband
  computation. (Ville)
- Refactor intel_vrr_max_hw_guardband() and use else for consistency.
  (Ville)

v4:
- Drop max_guardband from intel_vrr_max_hw_guardband(). (Ville)

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (#v2)
Link: https://lore.kernel.org/r/20250924141542.3122126-9-ankit.k.nautiyal@intel.com

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This commit is contained in:

Ankit Nautiyal 2025-09-24 19:45:40 +05:30

parent 94da8e5eee

commit 5f9172bf6f

1 changed files with 35 additions and 12 deletions

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

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