Full range of brightness using ACPIBacklight

[nguyenmac]

You should set XRGL to 3.

I will fix the Haswell one (eg. set it to one by default). Setting it to 1 or 0 is equivalent.

Also noticed I forgot to remove XOPT in the removal part of the data patch(es).

I don't understand, why shouldn't we use level 0? My laptop works fine with it.

 

[RehabMan]

I don't understand, why shouldn't we use level 0? My laptop works fine with it.

With it set to zero, it is possible to set the value to 1 or 2 which cause your display to blink/flicker. Because as you manipulate the slider in SysPrefs->Displays, ACPIBacklight could set a 1 or 2 if you're in the exact right spot. Also, during transition to off, it will hit 2, then 1, then zero, albeit at 1 and 2 only for a short period of time.

XRGL should be set to the lowest non-zero value your display can handle.

 

[nguyenmac]

With it set to zero, it is possible to set the value to 1 or 2 which cause your display to blink/flicker. Because as you manipulate the slider in SysPrefs->Displays, ACPIBacklight could set a 1 or 2 if you're in the exact right spot. Also, during transition to off, it will hit 2, then 1, then zero, albeit at 1 and 2 only for a short period of time.

XRGL should be set to the lowest non-zero value your display can handle.

Thank you for your explanation. I don't see any strange flicker yet, even in transition to off. I prefer value 0, the tiny light in level 3 annoys me.

 

[RehabMan]

Thank you for your explanation. I don't see any strange flicker yet, even in transition to off. I prefer value 0, the tiny light in level 3 annoys me.

You will never see the "tiny light in level 3" if you have the up-to-date patch. See post #169.

 

[nguyenmac]

You will never see the "tiny light in level 3" if you have the up-to-date patch. See post #169.

Thanks, it works now after changing XRGL to 3.

 

[philip_petev]

Thanks, it works now after changing XRGL to 3.

Just tried the same on my ProBook, works for me as well, probably for everyone too.

 

[RehabMan]

Just tried the same on my ProBook, works for me as well, probably for everyone too.

I think kpkp had issues with levels like 0x1f (31). So... we'll see...

 

[m.gbt2]

It wasn’t easy for me to collect the pieces in order to decently ask for support, so I’ll try to leave here my little help to the next ones.


1. Install ACPIBacklight Debug version
2. Install ioio to /usr/bin
3. Apply graphics_PNLF patch according to your processor microarchitecture (in my case, Sandy Bridge)
4. De-comment the whole Method (DEB1) from the just added Device (PNLF)
5. Do some experimenting with ioio


Once I did steps 1-4 and rebooted, my first impression is that the backlight is definitely higher than before. It used to be darker than the minimum one at Windows and now it is nearly equal the minimum.


Experimenting with ioio:
1. the following command has absolutely no effect, it doesn’t matter the value I place, I can even enter 0x0. The brightness slider in System Preferences > Display doesn’t move.

ioio -s ACPIBacklightPanel KLVX 0x710

2. the following command flickers my screen, for every value in the range 0x100 to 0x100000000… I don’t know how many zeros because I couldn’t read it, but I kept adding zeros to watch the effect. If out of that range (less than 0x100, more than 0x1000000..), the display turns off (or seems to).

ioio -s ACPIBacklightPanel RawBrightness 0x710

Originally, from Windows, my display should go from 0x111 to 0x122A.

Can you please recommend me new tests?
Attaching here my extracted system DSDT and IORegistryExplorer output.

 

[RehabMan]

It wasn’t easy for me to collect the pieces in order to decently ask for support, so I’ll try to leave here my little help to the next ones.


1. Install ACPIBacklight Debug version
2. Install ioio to /usr/bin
3. Apply graphics_PNLF patch according to your processor microarchitecture (in my case, Sandy Bridge)
4. De-comment the whole Method (DEB1) from the just added Device (PNLF)
5. Do some experimenting with ioio


Once I did steps 1-4 and rebooted, my first impression is that the backlight is definitely higher than before. It used to be darker than the minimum one at Windows and now it is nearly equal the minimum.


Experimenting with ioio:
1. the following command has absolutely no effect, it doesn’t matter the value I place, I can even enter 0x0. The brightness slider in System Preferences > Display doesn’t move.

ioio -s ACPIBacklightPanel KLVX 0x710

Setting KLVX by itself will have no effect until you set RawBrightness. And setting it to 0x710 will change nothing, as that is the default value for the patch (eg. it is already set to 0x710).

2. the following command flickers my screen, for every value in the range 0x100 to 0x100000000… I don’t know how many zeros because I couldn’t read it, but I kept adding zeros to watch the effect. If out of that range (less than 0x100, more than 0x1000000..), the display turns off (or seems to).

ioio -s ACPIBacklightPanel RawBrightness 0x710

Originally, from Windows, my display should go from 0x111 to 0x122A.

You should only set RawBrightness in the range 0 to KLVX (per Intel documentation). See what happens if you set KLVX to Windows levels (and RawBrightness):

ioio -s ACPIBacklightPanel KLVX 0x122a
ioio -s ACPIBacklightPanel RawBrightness 0x122a

Note: The ratio between RawBrightness/KLVX determines the PWM output and thus backlight level.

 

[m.gbt2]

See what happens if you set KLVX to Windows levels (and RawBrightness):

ioio -s ACPIBacklightPanel KLVX 0x122a
ioio -s ACPIBacklightPanel RawBrightness 0x122a

Flickering