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KGB-8375

Member

Registered: 2020-09-25

Posts: 4

[SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

When trying to change the brightness, the screen turns off and on again repeatedly. I have a Lenovo Ideapad Flex 5 15 IIL05 with an intel i7-1065G7 cpu.

For example, using

xbacklight -set 50

the screen will turn off for a second and on for a second, until I set it to maximum brightness again.

The brightness keys appear to work since KDE displays a brightness popup, however no matter what method I have tried, the screen just blinks on and off.

I've tried changing acpi_backlight to vendor, native, and video; none of those helped. I also tried using several other linux command line options, none of those seemed to have any effect. I also tried with and without the xf86-video-intel package.

Last edited by KGB-8375 (2020-10-01 13:39:04)

solskog

Member

Registered: 2020-09-05

Posts: 416

Re: [SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

Does this issue repeat in tty without X, when changing it manually?

$ cat /sys/class/backlight/intel_backlight/max_brightness
# echo NUMBER > /sys/class/backlight/intel_backlight/brightness

KGB-8375

Member

Registered: 2020-09-25

Posts: 4

Re: [SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

No, it continues to make the screen flash. It's also worth mentioning this is a brand new install, on the latest zen kernel (5.8.10). As I previously mentioned, I tried playing around with the kernel parameter acpi_backlight, which gave me the other options "thinkpad" which did nothing, and "acpi0" which also flashed the same way intel_backlight flashes.

Head_on_a_Stick

Member

From: London

Registered: 2014-02-20

Posts: 7,732

Website

Re: [SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

Perhaps check the PWM frequency: https://wiki.archlinux.org/index.php/Ba … i915_only)

It's a bit of a long shot and probably highly unlikely but it could be set *very* low.

---

Are you infected with Wetiko?

KGB-8375

Member

Registered: 2020-09-25

Posts: 4

Re: [SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

Using

sudo intel_reg read 0xC8254
                                    (0x000c8254): 0x05330064 (freq 1331, cycle 100)
sudo intel_reg write write 0xC8254 0x2998032

seemed to make it blink faster, leading me to think that it was helping. However using

sudo intel_reg read 0xC8254
                                    (0x000c8254): 0x05330064 (freq 1331, cycle 100)
sudo intel_reg write write 0xC8254 0x00533006

actually made my display cut off both in X and the TTY, forcing me to reboot. I don't know that this information is correct for current intel GPU's, or if I set the value too low?

EDIT:

I forgot to only change the upper 2 bits (oops!)

However changing the upper 2 bits does make it blink faster but not in the intended way. At 0x0053 the screen is at full brightness permanently until I set it to ~20%, where it is black and flashes to full brightness, and 0% where it's completely off.

Last edited by KGB-8375 (2020-09-28 18:51:41)

KGB-8375

Member

Registered: 2020-09-25

Posts: 4

Re: [SOLVED] Brightness not working on Lenovo Ideapad Flex 5 15

While using windows I checked Lenovo's update tool (Vantage) and saw there was a new BIOS update, revision ECCN29WW. Installing this removed my Grub UEFI boot entry, but after recreating it, this fixed the issue.