[Intel-gfx] vlv_disable_backlight causing warnings with i915 @ Xorg start

[Jani Nikula]

On Mon, 08 May 2017, Andrew Siplas <andrew at asip.xyz> wrote:
> At Xorg startup after a fresh compile of the mainline kernel, WARN_ON is
> truthy and throws a warning into the kernel's dmesg buffer.

Please file a bug at [1], add drm.debug=14 module parameter, add dmesg
from boot to reproducing the problem.

BR,
Jani.

[1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel

>
> I'm still trying to understand the driver, but it originates here:
>
> --
>
> static void vlv_disable_backlight(struct intel_connector *connector)
> {
>         struct drm_i915_private *dev_priv =
> to_i915(connector->base.dev);
>         enum pipe pipe = intel_get_pipe_from_connector(connector);
>         u32 tmp;
>
>         if (WARN_ON(pipe != PIPE_A && pipe != PIPE_B))
>                 return;
>
>         intel_panel_actually_set_backlight(connector, 0);
>
>         tmp = I915_READ(VLV_BLC_PWM_CTL2(pipe));
>         I915_WRITE(VLV_BLC_PWM_CTL2(pipe), tmp & ~BLM_PWM_ENABLE);
> }
>
> --
>
> Don't know yet what this means and so taking a chance this warning is
> something someone here might have some insight into / want to know about
> especially given the "...----[ cut here ]----...".
>
> The last two lines are from 5+ minutes after the warning but seem related:
>
>
> [   67.896233] ------------[ cut here ]------------
> [   67.896259] WARNING: CPU: 1 PID: 4276 at drivers/gpu/drm/i915/intel_panel.c:771 vlv_disable_backlight+0x86/0x90
> [   67.896261] Modules linked in: iptable_nat nf_nat_ipv4 nf_nat uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core videodev
> [   67.896299] CPU: 1 PID: 4276 Comm: Xorg Not tainted 4.11.0+ #2
> [   67.896303] Hardware name: HP HP Notebook/80C5, BIOS F.1E 12/25/2015
> [   67.896308] task: ffff8d6e75d79800 task.stack: ffff9a06c1218000
> [   67.896318] RIP: 0010:vlv_disable_backlight+0x86/0x90
> [   67.896323] RSP: 0018:ffff9a06c121b998 EFLAGS: 00010286
> [   67.896330] RAX: 0000000000000029 RBX: ffff8d6e76018000 RCX: ffffffff8ea56a78
> [   67.896335] RDX: 0000000000000001 RSI: 0000000000000092 RDI: ffffffff8ece6bcc
> [   67.896339] RBP: ffff9a06c121b9b0 R08: 0000000000000029 R09: 00000000000002d8
> [   67.896344] R10: 0000000000000000 R11: 0000000000000320 R12: ffff8d6e723c5000
> [   67.896348] R13: 00000000ffffffff R14: ffff8d6e7423e800 R15: ffff8d6e74ab9830
> [   67.896355] FS:  00007fb8d7e00a40(0000) GS:ffff8d6e7fc80000(0000) knlGS:0000000000000000
> [   67.896359] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   67.896364] CR2: 0000557bfe77dfd0 CR3: 0000000274d31000 CR4: 00000000001006e0
> [   67.896368] Call Trace:
> [   67.896383]  intel_panel_disable_backlight+0x51/0x80
> [   67.896391]  intel_edp_backlight_off+0x42/0x50
> [   67.896397]  intel_disable_dp+0x70/0xf0
> [   67.896407]  intel_encoders_disable.isra.103+0x82/0x90
> [   67.896416]  i9xx_crtc_disable+0x51/0x3b0
> [   67.896424]  ? intel_crtc_disable_planes+0xd4/0xf0
> [   67.896434]  intel_atomic_commit_tail+0x892/0xfb0
> [   67.896444]  ? insert_work+0x52/0x70
> [   67.896453]  ? __queue_work+0x12e/0x390
> [   67.896461]  ? intel_atomic_commit_ready+0x70/0x80
> [   67.896470]  intel_atomic_commit+0x3e6/0x4b0
> [   67.896479]  ? handle_conflicting_encoders+0x279/0x290
> [   67.896489]  drm_atomic_commit+0x46/0x50
> [   67.896497]  drm_atomic_helper_set_config+0x6b/0xa0
> [   67.896507]  __drm_mode_set_config_internal+0x62/0x110
> [   67.896514]  drm_mode_setcrtc+0x4ba/0x5a0
> [   67.896524]  drm_ioctl+0x326/0x430
> [   67.896532]  ? drm_mode_getcrtc+0x170/0x170
> [   67.896543]  do_vfs_ioctl+0x8f/0x5a0
> [   67.896552]  ? getnstimeofday64+0x9/0x20
> [   67.896561]  SyS_ioctl+0x74/0x80
> [   67.896569]  do_syscall_64+0x48/0xb0
> [   67.896580]  entry_SYSCALL64_slow_path+0x25/0x25
> [   67.896586] RIP: 0033:0x7fb8d5932507
> [   67.896590] RSP: 002b:00007ffe8bf43018 EFLAGS: 00003246 ORIG_RAX: 0000000000000010
> [   67.896598] RAX: ffffffffffffffda RBX: 0000561b92c11210 RCX: 00007fb8d5932507
> [   67.896602] RDX: 00007ffe8bf43140 RSI: 00000000c06864a2 RDI: 0000000000000009
> [   67.896607] RBP: 00007ffe8bf43140 R08: 0000561b92c11050 R09: 0000000000000001
> [   67.896611] R10: 0000000000000001 R11: 0000000000003246 R12: 00000000c06864a2
> [   67.896615] R13: 0000000000000009 R14: 0000561b92c13f70 R15: 00007fb8d7d67000
> [   67.896620] Code: df 41 8d b4 05 50 12 06 00 ff 93 f8 06 00 00 5b 41 5c 41 5d 5d c3 48 c7 c6 18 bc 88 8e 48 c7 c7 22 e8 82 8e 31 c0 e8 47 70 b6 ff <0f> ff eb e0 66 0f 1f 44 00 00 55 8b b7 f4 03 00 00 48 89 e5 e8 
> [   67.896771] ---[ end trace 528f42628325fc1b ]---
> [  490.370803] [drm] Atomic update on pipe (A) took 102 us, max time under evasion is 100 us
> [ 2623.216311] [drm] Atomic update on pipe (A) took 415 us, max time under evasion is 100 us
>
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-- 
Jani Nikula, Intel Open Source Technology Center