eDP VRR on Linux: Fixing Variable Refresh Rate for OLED Laptop Panels

Kernel patches and workarounds to enable VRR (Variable Refresh Rate) 20-120Hz on Intel eDP OLED panels where the OEM firmware doesn't set the VBT VRR flag.

Tested on Dell XPS 2026 (Intel Panther Lake, LG Display OLED 3200x2000) running CachyOS with the COSMIC desktop (cosmic-comp compositor). Should apply to any laptop with a VRR-capable eDP panel that works on Windows but not Linux.

The Problem

Your laptop's OLED panel supports VRR 20-120Hz. Windows uses it fine. Linux says vrr_capable: 0. Why?

Three bugs in the Linux display stack block eDP VRR:

Layer	Bug	Impact
DRM core (drm_edid.c)	Doesn't parse DisplayID v2.0 Adaptive Sync block (tag 0x2B) into monitor_range	Kernel doesn't know the VRR range
Intel driver (intel_vrr.c)	Gates eDP VRR on VBT firmware flag that OEMs don't set	vrr_capable=0 even with valid EDID
Compositor (smithay/cosmic-comp)	Returns NotSupported when vrr_capable=0	Compositor never tries VRR

Why it works on Windows

The Intel Windows driver reads the DisplayID Adaptive Sync block directly and doesn't require the VBT flag. AMD's Linux driver (amdgpu_dm.c) has its own workaround (parse_edid_displayid_vrr()). Intel's Linux driver just hasn't caught up.

The Fix

Part 1: Kernel Patches (for upstream)

Two patches in patches/:

0001-drm-edid-parse-displayid-adaptive-sync.patch -- Adds drm_get_monitor_range_displayid() to the DRM EDID parser. Reads the DisplayID v2.0 Adaptive Sync Data Block (tag 0x2B) and Dynamic Video Timing block (tag 0x25) as a fallback when the base EDID has no Range Limits descriptor. This is the generic fix that benefits all drivers.

0002-drm-i915-allow-edp-vrr-without-vbt.patch -- Relaxes the eDP VRR check in intel_vrr_is_capable(). Instead of requiring the VBT VRR flag, it also accepts a valid EDID monitor range (delta > 10Hz) as proof of VRR capability. The existing DPCD and range checks still apply.

Part 2: EDID Override (interim workaround)

Until the kernel patches land upstream, use an EDID override to inject a standard Range Limits descriptor that the existing kernel can parse:

# Generate the modified EDID from your panel
sudo python3 edid/generate-edid.py
sudo cp vrr.bin /lib/firmware/edid/

# Add to initramfs
# Edit /etc/mkinitcpio.conf:
#   FILES=(/lib/firmware/edid/vrr.bin)
sudo mkinitcpio -P

# Add kernel command line parameter
# (method depends on bootloader -- see configs/)
drm.edid_firmware=eDP-1:edid/vrr.bin

Part 3: Compositor Configuration

For COSMIC desktop (cosmic-comp), set VRR to force mode:

Edit ~/.local/state/cosmic-comp/outputs.ron and change vrr: r#false to vrr: force for your eDP output. Or use:

cosmic-randr mode eDP-1 <width> <height> --refresh <hz> --adaptive-sync true

Quick Start (CachyOS/Arch)

# 1. Generate and install EDID override
sudo python3 edid/generate-edid.py -o /lib/firmware/edid/vrr.bin

# 2. Add to initramfs
sudo sed -i 's/^FILES=.*/FILES=(\/lib\/firmware\/edid\/vrr.bin)/' /etc/mkinitcpio.conf
sudo mkinitcpio -P

# 3. Add kernel cmdline (Limine example)
# Edit /etc/default/limine, append to KERNEL_CMDLINE:
#   drm.edid_firmware=eDP-1:edid/vrr.bin xe.enable_dpcd_backlight=3

# 4. Build patched kernel (optional, for full fix)
cd cachyos/
makepkg -s --skippgpcheck

# 5. Enable VRR in compositor
# Edit ~/.local/state/cosmic-comp/outputs.ron: vrr: force

# 6. Reboot and verify
cosmic-randr list | grep Adaptive
# Should show: Adaptive Sync Support: true / Adaptive Sync: true

Verification

Check VRR capability

# vrr_capable should be 1
sudo modetest -c | grep -A3 vrr_capable

# VRR range should show your panel's range
sudo cat /sys/kernel/debug/dri/0/eDP-1/vrr_range

# VRR_ENABLED should be 1 when compositor has adaptive sync on
sudo modetest -p | grep -A3 VRR_ENABLED

Prove VRR is active (measure frame timing)

# Enable vblank tracing
sudo bash -c 'cd /sys/kernel/tracing && echo 1 > events/drm/drm_vblank_event_delivered/enable && echo 1 > tracing_on'

# Run something (move windows, play video, run glxgears)
sleep 3

# Analyze intervals
sudo bash -c 'echo 0 > /sys/kernel/tracing/tracing_on'
sudo python3 -c "
import re
with open('/sys/kernel/tracing/trace') as f:
    ts = [float(m.group(1)) for line in f if 'vblank_event_delivered' in line
          for m in [re.search(r'(\d+\.\d+):', line)] if m]
intervals = [(ts[i+1]-ts[i])*1000 for i in range(len(ts)-1) if 1 < (ts[i+1]-ts[i])*1000 < 60]
if intervals:
    print(f'Min: {min(intervals):.1f}ms ({1000/max(intervals):.0f}Hz)')
    print(f'Max: {max(intervals):.1f}ms ({1000/min(intervals):.0f}Hz)')
    print('VRR active!' if max(intervals)/min(intervals) > 1.3 else 'Fixed rate')
"

Example output showing VRR active (32-120Hz):

Vblank intervals (153 samples):
  Min: 8.324 ms (120 Hz)
  Max: 30.847 ms (32 Hz)
  *** VRR CONFIRMED ***

Affected Hardware

This fix applies to any laptop with:

• Intel GPU (xe or i915 driver)
• eDP OLED panel with VRR support
• DisplayID v2.0 extension with Adaptive Sync Data Block (tag 0x2B)
• OEM firmware (VBT) that does NOT set the VRR flag for eDP

Known affected:

• Dell XPS 2026 (Panther Lake, LG Display VNFT2 160WV1)
• Framework Laptop 13 (BOE NE135A1M-NY1) -- similar VBT issue
• Likely many other 2025-2026 laptops with eDP OLED panels

Technical Details

How we found the bugs

1. edid-decode shows the panel's EDID has an Adaptive Sync Data Block declaring 20-120Hz VRR
2. But vrr_capable=0 in the DRM connector properties
3. intel_vrr_is_capable() in intel_vrr.c returns false because:
   • Line 50: if (!connector->panel.vbt.vrr) return false; -- VBT flag not set by Dell
4. Even bypassing the VBT check, monitor_range is 0/0 because:
   • drm_get_monitor_range() in drm_edid.c only reads base EDID Range Limits (tag 0xFD)
   • The panel has no 0xFD descriptor -- range data is only in DisplayID tag 0x2B
   • AMD's driver has a private workaround; the generic DRM layer does not
5. The final check info->monitor_range.max_vfreq - info->monitor_range.min_vfreq > 10 also fails

DisplayID tag 0x2B vs 0x25

The kernel defines DATA_BLOCK_2_DYNAMIC_VIDEO_TIMING (0x25) but NOT the Adaptive Sync Data Block (0x2B). These are different DisplayID v2.0 block types:

• 0x25: Dynamic Video Timing Range Limits (similar to EDID Monitor Range)
• 0x2B: Adaptive Sync descriptor (specifically for VRR-capable panels)

Most modern eDP OLED panels use 0x2B. Our patch handles both.

DSC interaction

At 3200x2000@120Hz, Display Stream Compression (DSC) is active with 2 slices. The kernel has a joiner_pipes check that disables VRR when pipe joiner is active, but 2 DSC slices on a single pipe does NOT trigger joiner. VRR works fine with DSC.

Upstream Status

• No patches submitted yet
• Related: Adriano Vero's LKML patch for DisplayID monitor range parsing (similar approach, not merged)
• Intel Xe driver VRR refactoring ongoing in Linux 7.x

License

Kernel patches: GPL-2.0-only (matching Linux kernel) Scripts and configs: MIT