Fix drm_WARN_ON(common_len <= 0)

[koba]

[Impact]

The TGL machine could show drm_WARN_ON(common_len <= 0) when connect with the TBT dock(WD19TB).
------------[ cut here ]------------
i915 0000:00:02.0: drm_WARN_ON(common_len <= 0)
WARNING: CPU: 4 PID: 194 at drivers/gpu/drm/i915/display/intel_dp.c:2385 intel_dp_compute_link_config+0x820/0x900 [i915]
Modules linked in: i915(+) i2c_algo_bit drm_kms_helper crc32_pclmul syscopyarea sysfillrect sysimgblt fb_sys_fops cec rc_core nvme e1000e(+) c_i801 ahci i2c_smbus
thunderbolt(+) xhci_pci xhci_pci_renesas wmi video backlight pinctrl_tigerlake pinctrl_intel
CPU: 4 PID: 194 Comm: systemd-udevd Not tainted 5.10.0-051000rc7-generic #202012062330
Hardware name: Dell Inc. OptiPlex 7090 UFF - China HDD Protection/, BIOS 0.6.4 11/07/2020
RIP: 0010:intel_dp_compute_link_config+0x820/0x900 [i915]
Code: 4c 8b 77 50 4d 85 f6 75 03 4c 8b 37 e8 b9 b9 60 dc 48 c7 c1 b5 6d 83 c0 4c 89 f2 48 c7 c7 d0 69 83 c0 48 89 c6 e8 a5 84 f2 db <0f> 0b ff e9 60 f8 ff ff 48 8b
c2 60 04 82
RSP: 0018:ffffba120061f6b0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff956df17c2000 RCX: 0000000000000000
RDX: 000000000000002f RSI: ffffffff9e1b1dcf RDI: 0000000000000246
RBP: ffffba120061f720 R08: ffffffff9e1b1da0 R09: 000000000000002f
R10: ffffffff9e1b2180 R11: 000000009e1b1db2 R12: ffff956df1e40000
R13: ffff956df17c6000 R14: ffff956e029a99e0 R15: ffff956df17c6000
FS: 00007fbd08cdd880(0000) GS:ffff956e0e500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005635d4c41678 CR3: 0000000271c64006 CR4: 0000000000770ee0
PKRU: 55555554
Call Trace:
? dev_printk+0x5d/0x74
intel_dp_compute_config+0x11b/0x570 [i915]
intel_ddi_compute_config+0x9f/0xe0 [i915]
intel_modeset_pipe_config+0x212/0x9c0 [i915]
intel_atomic_check+0x263/0x12c0 [i915]
? __drm_dbg+0x87/0x90 [drm]
drm_atomic_check_only+0x2c7/0x450 [drm]
drm_atomic_commit+0x18/0x50 [drm]
intel_modeset_init_nogem+0x486/0xb10 [i915]
i915_driver_probe+0x3e8/0x6e0 [i915]
? mutex_lock+0x13/0x40
i915_pci_probe+0x5a/0x140 [i915]
local_pci_probe+0x48/0x80
pci_device_probe+0x10f/0x1c0
really_probe+0x1db/0x440
driver_probe_device+0xe9/0x160
device_driver_attach+0x5d/0x70
__driver_attach+0x8f/0x150
? device_driver_attach+0x70/0x70
bus_for_each_dev+0x7e/0xc0
driver_attach+0x1e/0x20
bus_add_driver+0x152/0x1f0
driver_register+0x74/0xd0
__pci_register_driver+0x54/0x60
i915_init+0x61/0x75 [i915]
? 0xffffffffc08a1000
do_one_initcall+0x4a/0x1fa
? _cond_resched+0x19/0x30
? kmem_cache_alloc_trace+0x17e/0x2f0
do_init_module+0x62/0x240
load_module+0xfbe/0x11e0
__do_sys_finit_module+0xbe/0x120
? __do_sys_finit_module+0xbe/0x120
__x64_sys_finit_module+0x1a/0x20
do_syscall_64+0x38/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fbd0925f89d
Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 73 01 c3 48 8b 0d c3 f5 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007fffa60dc628 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 00005635d4c942b0 RCX: 00007fbd0925f89d
RDX: 0000000000000000 RSI: 00007fbd0913cded RDI: 0000000000000014
RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000014 R11: 0000000000000246 R12: 00007fbd0913cded
R13: 0000000000000000 R14: 00005635d4c92b70 R15: 00005635d4c942b0
---[ end trace c48f367c543f3384 ]-—

[Fix]

Kernel driver patchset https://patchwork.freedesktop.org/series/82173/ targeting v5.11.

[Test Case]

1. Boot with kernel built with these patches applied.
2. check the dmesg.

[Where problems could occur]

The fix could resolve the drm_WARN_ON.
It ease the symptom that can't output the video with the TBT dock(WD19TB) at the first boot, but it may not fix.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1908885

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Timo Aaltonen (tjaalton)]

committed, but without a BugLink so status tracking doesn't work

[Timo Aaltonen (tjaalton)]

fixed in 1009