[PATCH 0/2] drm/i915/display: Enable AS SDP Skip Frames

[Uma Shankar <uma.shankar@intel.com>]

When Panel Replay is active the transcoder timing generator runs at the
panel's maximum refresh rate, but content is often presented at a lower
rate. In that case the Adaptive-Sync SDP (AS SDP) only needs to reach the
panel often enough to satisfy its maximum frame time, so transmitting it
on every frame is redundant and shows up as repeated SDPs on the link.

Xe3LPD adds a HW skip-frame counter in PR_ALPM_CTL that lets the source
send a single AS SDP and then suppress it for a programmed number of
frames. Program this counter so that one AS SDP is followed by
(max_vrefresh / flip_rate - 1) idle frames, matching the effective
content rate and allowing the link to be driven down to as low as 1Hz
when the hardware supports it.

ToDo: Currently using CMRR debugfs as an interface to get the flip rate
from userspace, this will be extended to a property interface to receive
actual content fps as follow up.

Uma Shankar (2):
  drm/i915/display: Enable AS SDP Skip Frames
  drm/i915/display: Keep AS SDP flowing when skip frames is enabled

 drivers/gpu/drm/i915/display/intel_alpm.c     | 65 +++++++++++++++++--
 drivers/gpu/drm/i915/display/intel_psr_regs.h |  2 +
 2 files changed, 62 insertions(+), 5 deletions(-)

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2.50.1