[PATCH 0/2] drm/i915/intel_panel: Fix seamless VRR mode switching for DRRS panels

[Ankit Nautiyal <ankit.k.nautiyal@intel.com>]

Currently intel_panel_fixed_mode() can return a lower refresh rate mode
for VRR panels if the lower refresh rate mode is first in the list.
This creates problems for seamless switch features like LRR and
Seamless-DRRS, as it results in changes to vsync_start/end causing a
full modeset instead of a seamless switch.

This is particularly problematic for DRRS panels on platforms without
double buffered M/N support for LNL+ (display version 20+), where
seamless clock changes are not possible.

This series attempts to fixe this by:
1. Adding a helper to get the highest refresh rate mode from the list of
   fixed modes for a connector.
2. When a seamless switch to a lower mode is desired, making
   intel_panel_fixed_mode() return the highest refresh rate mode,
   provided the requested rate is in VRR range. The vblank is then
   extended to provide the desired refresh rate.

To determine whether a full modeset or seamless switch is intended, the
connector state is checked for the allow_modeset flag. A nullable
conn_state parameter is added to intel_panel_fixed_mode() and
intel_panel_compute_config() for this purpose.

Ankit Nautiyal (2):
  drm/i915/intel_panel: Add a helper to get the highest refresh rate
    mode
  drm/i915/intel_panel: Use highest refresh rate mode for seamless VRR
    changes

 drivers/gpu/drm/i915/display/icl_dsi.c     |  2 +-
 drivers/gpu/drm/i915/display/intel_dp.c    |  6 +--
 drivers/gpu/drm/i915/display/intel_dsi.c   |  2 +-
 drivers/gpu/drm/i915/display/intel_dvo.c   |  6 +--
 drivers/gpu/drm/i915/display/intel_lvds.c  |  4 +-
 drivers/gpu/drm/i915/display/intel_panel.c | 50 ++++++++++++++--------
 drivers/gpu/drm/i915/display/intel_panel.h |  8 +++-
 drivers/gpu/drm/i915/display/intel_sdvo.c  |  8 ++--
 drivers/gpu/drm/i915/display/vlv_dsi.c     |  2 +-
 9 files changed, 54 insertions(+), 34 deletions(-)

-- 
2.45.2