Bug 111095 - Backlight flicker after suspend on certain Intel CherryTrail tablets
Summary: Backlight flicker after suspend on certain Intel CherryTrail tablets
Status: NEW
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Intel (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: high normal
Assignee: Intel GFX Bugs mailing list
QA Contact: Intel GFX Bugs mailing list
URL:
Whiteboard: Triaged, ReadyForDev
Keywords:
Depends on:
Blocks:
 
Reported: 2019-07-09 12:51 UTC by russianneuromancer
Modified: 2019-08-21 14:10 UTC (History)
4 users (show)

See Also:
i915 platform: BSW/CHT
i915 features: display/backlight, display/DSI


Attachments
drm-tip dmesg with drm.debug=0x1e from Irbis TW90 (1.62 MB, text/plain)
2019-07-09 12:51 UTC, russianneuromancer
no flags Details
drm-tip dmesg with drm.debug=0x1e from Lenovo Miix 320-10ICR (1.15 MB, text/plain)
2019-07-09 12:58 UTC, russianneuromancer
no flags Details
i915_vbt from Lenovo Miix320-10ICR (7.00 KB, application/octet-stream)
2019-08-21 14:10 UTC, russianneuromancer
no flags Details

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Description russianneuromancer 2019-07-09 12:51:07 UTC
Created attachment 144739 [details]
drm-tip dmesg with drm.debug=0x1e from Irbis TW90

Hello!

I find that backlight is flicker after suspend on certain Intel CherryTrail tablets. In particular, I reproduced this issue on Irbis TW90 and Lenovo Miix 320-10ICR. There is few ways of reproducing this issue, none is 100% reliable, but in general it boiling down to several suspend/wakeup cycles for a period of few hours. In attached Irbis TW90 log issue happened after two suspend/wakeup cycles, every suspend lasted for a ~3 hours. 

Other symptoms: 
1. When backlight flicker occur brightness adjustment to 10-20% level makes screen completely black (backlight is disabled). This doesn't happen before suspend.
2. When backlight flicker occur brightness adjustment to 100% allow to temporary workaround issue at cost of battery time.
3. Reboot or power cycle usually doesn't help. When backlight flicker started it continue to happen everywhere, even in BIOS.

Logs from drm-tip/2019-07-05 (ad5a0afdd20635e644d13406e1d1a7ec44398e0e) with drm.debug=0x1e from both devices is attached.
Comment 1 russianneuromancer 2019-07-09 12:58:12 UTC
Created attachment 144740 [details]
drm-tip dmesg with drm.debug=0x1e from Lenovo Miix 320-10ICR

Additional information about hardware and software:
Both devices have Intel Atom x5-Z8350 CPU and 2GB RAM. Both devices run Ubuntu 19.04 with Gnome Shell 3.32.2 session in Wayland mode and 200% scaling. libdrm version is 2.4.97
Comment 2 russianneuromancer 2019-07-09 16:27:28 UTC
Other user found that issue is also reproducible on Irbis TW52 tablet: http://4pda.ru/forum/index.php?showtopic=942823&view=findpost&p=86750476
Comment 3 Lakshmi 2019-07-10 05:35:21 UTC
@Jani/Imre, any suggestions here?
Comment 4 Jani Nikula 2019-08-01 09:13:14 UTC
(In reply to russianneuromancer from comment #0)
> 3. Reboot or power cycle usually doesn't help. When backlight flicker
> started it continue to happen everywhere, even in BIOS.

How do you recover from this?
Comment 5 russianneuromancer 2019-08-01 11:00:48 UTC
> How do you recover from this?

Poweroff tablet for a ten minutes or so. User mentioned in Comment 2 said that eventually flicker go away if tablet is powered on too, but I didn't tried that.
Comment 6 russianneuromancer 2019-08-05 12:33:50 UTC
Issue it reproducible with Linux 5.3rc3.
Comment 7 Lakshmi 2019-08-13 06:52:06 UTC
(In reply to russianneuromancer from comment #5)
> > How do you recover from this?
> 
> Poweroff tablet for a ten minutes or so. User mentioned in Comment 2 said
> that eventually flicker go away if tablet is powered on too, but I didn't
> tried that.

@Jani any further comments here?
Comment 8 russianneuromancer 2019-08-13 07:17:39 UTC
> User mentioned in Comment 2 said that eventually flicker go away if tablet is powered on too, but I didn't tried that.

Tested this couple of days ago with rc3, I tried to left Lenovo Miix320-10ICR powered on with flicker screen for two hours, and flicker doesn't go away. So this does not help in my case.

> Poweroff tablet for a ten minutes or so.

It seems like this was necessary with Linux 5.0/5.1, but with more recent kernels (Linux 5.3 and drm-tip) simple reboot was sufficient, at least latest two times I tried to do this.

Please let me know if I should test few latest Linux releases to find out since when reboot starting to be sufficient to workaround this issue.
Comment 9 Jani Nikula 2019-08-13 09:06:23 UTC
I'm not sure what to look for, but let's check some basics first. Please provide the output of

# intel_reg read 0x180000:0x61250 0x180000:0x61254 0x180000:0x61350 0x180000:0x61354

before and after it starts flickering. intel_reg is part of igt-gpu-tools.
Comment 10 Hans de Goede 2019-08-13 09:33:26 UTC
Jani, note that the affected devices are using the LPSS PWM controller for backlight control (AFAICT).
Comment 11 Jani Nikula 2019-08-13 13:26:03 UTC
Hum, is that right?

Please attach /sys/kernel/debug/dri/0/i915_vbt
Comment 12 russianneuromancer 2019-08-21 14:10:27 UTC
Created attachment 145114 [details]
i915_vbt from Lenovo Miix320-10ICR

> Please attach /sys/kernel/debug/dri/0/i915_vbt

Attached.


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