loading i915kms in ThinkPad X13 Intel Gen2 will hang up.

[takawata]

Describe the bug
loading i915kms gets screen blackout. Try it from remote login, it probed that the initialization routine is hanging and did not return from kldload(8).
typing ^Z did not return to prompt, and ^T shows
load: 0x43 cmd:kldload 1762 [running] 8.54r 0.00u 8.50s 58% 2296k intel_ddi_compute_config+0x3f,intel_atomic_check+0x65a, drm_atomic_check_only+0x400, drm_atomic_commit+0x13 intel_modeset_init+0x1e28 i915_driver_probe+0xe39 i915_probe+0x42 linux_pci_attach_device+0x43b device_attach+0x3c3 bus_generic_driver_added+0xa1 devclass_driver_added+0x39 devclass_add_driver+0x13d _linux_pci_register_driver+0xcc i915kms_evh+0x39 module_register_init+0xa4 linker_load_module+0xbad kern_kldload=0x16a sys_kldload+0x5b
FreeBSD version
Paste the output of uname -a
FreeBSD 14.0-CURRENT #12 takawata-wip-n254513-7a473c2ec3b9-dirty: Fri Apr 8 22:
37:25 JST 2022

PCI Info
vgapci0@pci0:0:2:0: class=0x030000 rev=0x01 hdr=0x00 vendor=0x8086 device=0x9a49 subvendor=0x17aa subdevice=0x22d1
vendor = 'Intel Corporation'
device = 'TigerLake-LP GT2 [Iris Xe Graphics]'
class = display
subclass = VGA
DRM KMOD version
master

To Reproduce
loading i915kms.ko

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Add any other context about the problem here.

[takawata]

The dmesg when the module is loaded is as follows.

iic0: <I2C generic I/O> on iicbus0
iic1: <I2C generic I/O> on iicbus1
drmn0: on vgapci0
vgapci0: child drmn0 requested pci_enable_io
vgapci0: child drmn0 requested pci_enable_io
[drm] Unable to create a private tmpfs mount, hugepage support will be disabled(-19).
[drm] Got stolen memory base 0x0, size 0x0
[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
lkpi_iic0: on drmn0
iicbus2: on lkpi_iic0
iic2: <I2C generic I/O> on iicbus2
lkpi_iic1: on drmn0
iicbus3: on lkpi_iic1
iic3: <I2C generic I/O> on iicbus3
lkpi_iic2: on drmn0
iicbus4: on lkpi_iic2
iic4: <I2C generic I/O> on iicbus4
lkpi_iic3: on drmn0
iicbus5: on lkpi_iic3
iic5: <I2C generic I/O> on iicbus5
lkpi_iic4: on drmn0
iicbus6: on lkpi_iic4
iic6: <I2C generic I/O> on iicbus6
lkpi_iic5: on drmn0
iicbus7: on lkpi_iic5
iic7: <I2C generic I/O> on iicbus7
lkpi_iic6: on drmn0
iicbus8: on lkpi_iic6
iic8: <I2C generic I/O> on iicbus8
lkpi_iic7: on drmn0
iicbus9: on lkpi_iic7
iic9: <I2C generic I/O> on iicbus9
lkpi_iic8: on drmn0
iicbus10: on lkpi_iic8
iic10: <I2C generic I/O> on iicbus10
[drm] Connector eDP-1: get mode from tunables:
[drm] - kern.vt.fb.modes.eDP-1
[drm] - kern.vt.fb.default_mode
drmn0: successfully loaded firmware image 'i915/tgl_dmc_ver2_06.bin'
drmn0: [drm] Finished loading DMC firmware i915/tgl_dmc_ver2_06.bin (v2.6)
[drm] Connector HDMI-A-1: get mode from tunables:
[drm] - kern.vt.fb.modes.HDMI-A-1
[drm] - kern.vt.fb.default_mode
[drm] Connector DP-1: get mode from tunables:
[drm] - kern.vt.fb.modes.DP-1
[drm] - kern.vt.fb.default_mode
[drm] Connector DP-2: get mode from tunables:
[drm] - kern.vt.fb.modes.DP-2
[drm] - kern.vt.fb.default_mode
[drm] Connector DP-3: get mode from tunables:
[drm] - kern.vt.fb.modes.DP-3
[drm] - kern.vt.fb.default_mode
[drm] Connector DP-4: get mode from tunables:
[drm] - kern.vt.fb.modes.DP-4
[drm] - kern.vt.fb.default_mode
drmn drmn0: drm_WARN_ON(common_len <= 0)

[evadot]

Did it worked before ?
If yes could you bisect ?
Thanks

[takawata]

Never. I tried drm-kmod-current ports and did not work , then I try the master .

[evadot]

drmn drmn0: drm_WARN_ON(common_len <= 0) seems to be displayport related.
Can you try without external screen/dock etc ... ?

[takawata]

I don't connect anything but ethernet cable when I got the message.

[takawata]

Ignoreing DP initialization after common_len <= 0 then module loading success and seems to X work, though non-X console resolution did not change as usual.

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c 
b/drivers/gpu/drm/i915/display/intel_dp.c

index 70831e738f..7ef06791e8 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2355,7 +2355,10 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
        common_len = intel_dp_common_len_rate_limit(intel_dp,
                                                   intel_dp->max_link_rate);
-
+       if(common_len <= 0)
+       {
+               return -EINVAL;
+       }
       /* No common link rates between source and sink */        　　　　 
drm_WARN_ON(encoder->base.dev, common_len <= 0);

Xorg.0.log

[takawata]

drm-510-kmod still hang up, This patch is still needed, it seems.

[evadot]

Using 5.15-lts or 6.1-lts will fix this.