linux-ptl: enable PSR2 selective update on OLED panels

[TsaiGaggery]

Summary

• Add three display driver patches to enable PSR2 + VRR on Panther Lake eDP OLED panels
• Fixes PSR2 being silently rejected due to SU granularity read from wrong DPCD registers
• Removes blanket VRR rejection that prevented PSR2 + VRR coexistence

Patches

0019-drm-i915-psr-accept-early-transport-for-psr2.patch
Accept Early Transport (DPCD version 0x04) for PSR2 sink support.

0020-drm-i915-psr-fix-su-granularity-source-for-psr2.patch
Fix SU granularity register source when Panel Replay is disabled. Without this, PSR2 reads Panel Replay X granularity (0xFFFF) causing 2880 % 65535 != 0 failure.

0022-psr-allow-vrr.patch
Remove blanket VRR rejection in _psr_compute_config(). The existing Wa_16011303918 in intel_psr2_config_valid() already handles the Alderlake-P stepping-specific VRR incompatibility. On PTL, PSR2 + VRR works correctly.

Root cause

All three patches fix kernel code issues, not panel problems:

1. ET acceptance: kernel didn't recognize DPCD 0x04 (Early Transport) as valid PSR2
2. Granularity: kernel read Panel Replay DPCD (0xB2=0xFFFF) instead of PSR2 DPCD (0x72=4) when PR is disabled but supported
3. VRR rejection: _psr_compute_config() had if (crtc_state->vrr.enable) return false blocking ALL PSR with VRR on ALL platforms, even though only ADL-P A0/B0 has a known issue

In upstream drm-intel-next, issues 1-2 are solved by architectural refactoring. Issue 3 is handled differently — upstream blocks PSR+VRR but enables Panel Replay+VRR instead.

Power measurements

Dell XPS 14 OLED (Panther Lake B0, LG Display 2880x1800, eDP 1.5).
90s settle + 60s measure, no debugfs reads, screensaver disabled.

Mode	Package (mW)	Psys (mW)
PSR2 (Early Transport)	800	1384
PSR1	816	1442
PSR disabled	981	1597

PSR2 saves ~213 mW Psys (13%) vs PSR disabled.

Test results

PSR2 + VRR both active from boot:

PSR mode: PSR2 enabled (Early Transport)
Source PSR/PanelReplay status: DEEP_SLEEP
PSR2 selective fetch: enabled
vrr: true (20-120Hz)

Configuration

/etc/modprobe.d/xe-psr2.conf:
    options xe enable_psr=2 enable_panel_replay=0

~/.config/hypr/monitors.conf:
    monitor=,preferred,auto,auto,vrr,1

Notes

• Not cherry-picked from upstream. In drm-intel-next, PTL uses Panel Replay SU (not PSR2) with VRR.
• Panel Replay has cursor lag (~10Hz) on Dell XPS + LGD OLED — upstream quirk QUIRK_DISABLE_EDP_PANEL_REPLAY (45c77d4bf8d4). PSR2 has no cursor lag.
• Boot message Selective fetch area calculation failed in pipe A is a known PTL issue. Does not affect PSR2 operation.
• Requires PR Backport DisplayID adaptive sync VRR parsing #72 (DisplayID adaptive sync VRR parsing) for VRR on XPS 16. XPS 14 detects VRR without it but PR Backport DisplayID adaptive sync VRR parsing #72 is included for compatibility.