drm/i915/vblank: Add helper to get correct vblank length

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Currently crtc_vblank_start is assumed to be the vblank_start for the fixed
refresh rate case. That value can be different from the variable refresh
rate case whenever always_use_vrr_tg()==false. On icl/tgl it's always
different due to the extra vblank delay, and also on adl+ it could be
different if we were to use an optimized guardband.

So places where crtc_vblank_start is used to compute vblank length needs
change so as to account for cases where vrr is enabled. Specifically
with vrr.enable the effective vblank length is actually guardband.

Add a helper to get the correct vblank length for both vrr and fixed
refresh rate cases. Use this helper where vblank_start is used to
compute the vblank length.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/20251016055415.2101347-5-ankit.k.nautiyal@intel.com

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This commit is contained in:

Ankit Nautiyal 2025-10-16 11:24:08 +05:30

parent 2cdcab0d3a

commit ca4edafa14

3 changed files with 14 additions and 1 deletions

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10

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

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2

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

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3

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

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