Bug 677694 - /sys/class/backlight/nv_backlight/max_brightness is set to lower value after suspend on battery power giving dim display
/sys/class/backlight/nv_backlight/max_brightness is set to lower value after ...
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
Depends On:
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Reported: 2011-02-15 10:53 EST by Greg Crichton
Modified: 2011-02-21 07:02 EST (History)
6 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2011-02-21 07:02:38 EST
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Regression: ---
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
lspci -vv -nn -d 10de:0a29 (2.73 KB, application/octet-stream)
2011-02-15 10:53 EST, Greg Crichton
no flags Details
/var/log/messages excerpt after issue (408.31 KB, application/octet-stream)
2011-02-15 11:02 EST, Greg Crichton
no flags Details
Xorg log (29.86 KB, application/octet-stream)
2011-02-15 11:03 EST, Greg Crichton
no flags Details

  None (edit)
Description Greg Crichton 2011-02-15 10:53:22 EST
Created attachment 478899 [details]
lspci -vv -nn -d 10de:0a29

Description of problem:
On boot with updated Rawhide on Samsung R590 laptop (Nvidea GM330) /sys/class/backlight/nv_backlight/max_brightness is set to 1073864551
The brightness is fine for viewing and controllable via keys. If power cable is connected suspend/resume is ok and the brightness consistent.
However, when on battery power a resume comes back with a very dim display and max_brightness is set to 1025. Keys work for adjusting brightness but do not get more than very dim.
Attempting to exceed the now lower max_value results in:
echo 1026 > /sys/class/backlight/nv_backlight/brightness 
-bash: echo: write error: Invalid argument
(attempted writing large value to max_brightness results in permission denied)

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Boot, login. 
2. Note /sys/class/backlight/nv_backlight/max_brightness is 1073864551. 
3. Run on battery and suspend/resume. Note dimmed display and changed max_brightness value.
Actual results:
Display is dim. Brightness keys go to max but display is still too dark to use.
/sys/class/backlight/nv_backlight/max_brightness is set to 1025

Expected results:
Brightness returns to normal levels. 

Additional info:
Possibly related to https://bugzilla.redhat.com/show_bug.cgi?id=625171
In which case it is the initial max_brightness value is incorrect (but which works).
Comment 1 Greg Crichton 2011-02-15 11:02:57 EST
Created attachment 478900 [details]
/var/log/messages excerpt after issue
Comment 2 Greg Crichton 2011-02-15 11:03:46 EST
Created attachment 478901 [details]
Xorg log
Comment 3 Greg Crichton 2011-02-21 07:02:38 EST
This has been fixed with latest updates.

/sys/class/backlight/acpi_video0/max_brightness is now 7
Removing power dims the screen but using keyboard it can be increased to 7.

/sys/class/backlight/nv_backlight is no longer present.

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