[POCO M3 Pro / Redmi Note 10 5G] Screen won't wake

[DavidPinilo]

Screen won't wake for notifications. Also in low light conditions, screen brightness seems to fall to 0 and although the screen works, you can't see anything logcat_04-26-2022_09-03-04.txt g Device: POCO M3 Pro / Redmi Note 10 5G AOSP 12.1 v412

[malfunchan]

while debugging this issue, I found that the backlight service sends two backlight signals. one to /sys/class/leds/lcd-backlight/brightness and another to /sys/class/leds/lcd-backlight/brightness_clone. However, the data that gets sent to brightness_clone is the real backlight values that are supposed to be in brightness.

Here's a logcat snippet while sliding the brightness slider up:

05-17 05:06:54.949  1056  1056 D android.hardware.lights-service.mediatek: write 3436 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:54.950  1056  1056 D android.hardware.lights-service.mediatek: write 1717 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:54.966  1056  1056 D android.hardware.lights-service.mediatek: write 3452 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:54.966  1056  1056 D android.hardware.lights-service.mediatek: write 1725 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:54.983  1056  1056 D android.hardware.lights-service.mediatek: write 3468 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:54.984  1056  1056 D android.hardware.lights-service.mediatek: write 1733 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.019  1056  1056 D android.hardware.lights-service.mediatek: write 3500 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.019  1056  1056 D android.hardware.lights-service.mediatek: write 1749 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.035  1056  1056 D android.hardware.lights-service.mediatek: write 3516 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.035  1056  1056 D android.hardware.lights-service.mediatek: write 1757 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.048  1056  1056 D android.hardware.lights-service.mediatek: write 3532 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.048  1056  1056 D android.hardware.lights-service.mediatek: write 1765 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.067  1056  1056 D android.hardware.lights-service.mediatek: write 3549 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.067  1056  1056 D android.hardware.lights-service.mediatek: write 1774 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.084  1056  1056 D android.hardware.lights-service.mediatek: write 3565 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.085  1056  1056 D android.hardware.lights-service.mediatek: write 1782 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.118  1056  1056 D android.hardware.lights-service.mediatek: write 3597 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.118  1056  1056 D android.hardware.lights-service.mediatek: write 1798 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.132  1056  1056 D android.hardware.lights-service.mediatek: write 3645 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.132  1056  1056 D android.hardware.lights-service.mediatek: write 1822 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.149  1056  1056 D android.hardware.lights-service.mediatek: write 3709 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.149  1056  1056 D android.hardware.lights-service.mediatek: write 1854 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.168  1056  1056 D android.hardware.lights-service.mediatek: write 3757 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.168  1056  1056 D android.hardware.lights-service.mediatek: write 1878 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.202  1056  1056 D android.hardware.lights-service.mediatek: write 3789 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.202  1056  1056 D android.hardware.lights-service.mediatek: write 1894 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.218  1056  1056 D android.hardware.lights-service.mediatek: write 3838 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.218  1056  1056 D android.hardware.lights-service.mediatek: write 1918 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.233  1056  1056 D android.hardware.lights-service.mediatek: write 3902 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.233  1056  1056 D android.hardware.lights-service.mediatek: write 1950 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.268  1056  1056 D android.hardware.lights-service.mediatek: write 3934 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.268  1056  1056 D android.hardware.lights-service.mediatek: write 1966 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.288  1056  1056 D android.hardware.lights-service.mediatek: write 3998 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.288  1056  1056 D android.hardware.lights-service.mediatek: write 1998 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.300  1056  1056 D android.hardware.lights-service.mediatek: write 4046 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.300  1056  1056 D android.hardware.lights-service.mediatek: write 2022 to /sys/class/leds/lcd-backlight/brightness, result: 0
05-17 05:06:55.316  1056  1056 D android.hardware.lights-service.mediatek: write 4095 to /sys/class/leds/lcd-backlight/brightness_clone, result: 0
05-17 05:06:55.316  1056  1056 D android.hardware.lights-service.mediatek: write 2047 to /sys/class/leds/lcd-backlight/brightness, result: 0

As you probably can tell, brightness_clone is more consistent and accurate than brightness, so i made a loop to take all brightness_clone values and send them to brightness and the brightness values are fixed. while true; do cat /sys/class/leds/lcd-backlight/brightness_clone > /sys/class/leds/lcd-backlight/brightness_clone; done With this running in the background I can use the whole slider and brightness go as low as 13 and as high as 4095 (max, after setting persist.sys.qcom-brightness to 4095).

I still don't know how to fix this but at least we now know the cause of it.

(and yeah this is the cause to 0 backlight issue after sleep)

[phhusson]

Sorry for not updating the infos here, I actually debugged this issue few days ago...

What you said is right, though it doesn't explain the details. So:

• "Use alternate backlight scale" which changes lights called to call setLights with brightness rather than ARGB is required, but it assumes that the max is the content of /sys/class/leds/lcd-backlight/max_brightness. On this device, it's wrong, it's 4095, because the lights HAL does *=2 on the light value (probably because all Xiaomi devices use 4095 scale, and didn't bother to change for that one)
• Both enabling that option and setting it in 4095 is done in https://github.com/phhusson/device_phh_treble/commit/71f0000b6a9586307233c0c4ba83eb3181db0e13
• Between 400 and 4095, the values are properly transmitted by the Lights HAL to brightness not-clone as-is
• Under 400, it's not transmitted at all (hence the potential 0 backlight after sleep)
• Xiaomi's Android framework sends 400 when the user sets it to lower than 400
• Xiaomi's Android framework triggers DC diming when under 400, using Mediatek's setColorMatrix_3x3 (so instead of sending identity matrix [[1,0,0],[0,1,0],[0,0,1]] it sends [[0.8,0,0],[0,0.8,0],[0,0,0.8]])
• If Xiaomi switch to DC diming, it's probably because that real diming under 400 isn't nice with color artifacts

So the first part (>=400) of the issue is fixed, but the under 400 sounds uh, extremely annoying. I can technically add a giant hack where Android's framework writes directly in /sys/class/leds/lcd-backlight/brightness, but this will most likely break various stuff (well, you have no AOD, so at least I can't break AOD...)

[brian0309]

hello thanks for the code. It helps! Also i created temporary magisk module to run it on boot, it's working fine now ^^ you guys are awesome! magisk

[phhusson]

FYI the while command eats 100% of one CPU, which will kill your battery life

[malfunchan]

• "Use alternate backlight scale" which changes lights called to call setLights with brightness rather than ARGB is required, but it assumes that the max is the content of /sys/class/leds/lcd-backlight/max_brightness. On this device, it's wrong, it's 4095, because the lights HAL does *=2 on the light value (probably because all Xiaomi devices use 4095 scale, and didn't bother to change for that one)

Makes sense. It's Xiaomi we're talking about.

• Both enabling that option and setting it in 4095 is done in phhusson/device_phh_treble@71f0000

At the time of writing, I didn't know that.

• Xiaomi's Android framework triggers DC diming when under 400, using Mediatek's setColorMatrix_3x3 (so instead of sending identity matrix [[1,0,0],[0,1,0],[0,0,1]] it sends [[0.8,0,0],[0,0.8,0],[0,0,0.8]])

Interesting.

• If Xiaomi switch to DC diming, it's probably because that real diming under 400 isn't nice with color artifacts

Well from what I tried there are no artifacts or anything wrong with the display under 400 using the loop I mentioned above, which as you mentioned eats battery and prevents the device from sleep.

So the first part (>=400) of the issue is fixed, but the under 400 sounds uh, extremely annoying. I can technically add a giant hack where Android's framework writes directly in /sys/class/leds/lcd-backlight/brightness, but this will most likely break various stuff (well, you have no AOD, so at least I can't break AOD...)

Well... I was about to try playing with the lights service in aosp and try to implement DC Dimming but instead I looked at android.hardware.lights-service.mediatek since it's the one writing to brightness_clone and did a string edit using HxD and... it worked! as silly as it is.

in offset 00001BB0, there's a single mention of brightness_clone. fill "_clone" with 00 and push it to /vendor/bin/hw. that's it. Brightness works perfectly.

I'll make a magisk module when I'm off work and send it here.

[phhusson]

You can probably just do mount -o bind /sys/..../brightness_clone /sys/.../brightness from rw-system.sh instead

[malfunchan]

You can probably just do mount -o bind /sys/..../brightness_clone /sys/.../brightness from rw-system.sh instead

Not sure why this hasn't came to mind when I was brainstorming a solution... but at least I came up with one, I guess...

[phhusson]

meh, you already had a solution, i just improved yours a tiny bit But so can you try it, and PR the modified rw-system.sh if it works? it's always better to have the workaround in gsi rather than as a separate magisk module

[malfunchan]

meh, you already had a solution, i just improved yours a tiny bit But so can you try it, and PR the modified rw-system.sh if it works? it's always better to have the workaround in gsi rather than as a separate magisk module

Unfortunately it didn't work.

[malfunchan]

Here's the magisk module for now until we find another way to fix it.

Camellia Brightness fix.zip

[malfunchan]

Interesting... I used begonia's lightservice.mediatek file and it completely fixed brightness. no need for linear brightness either. The mod I did kept writing two values to brightness over 400 so it didn't give full brightness. While I tried different mods like removing the second "real" brightness line from camellia's lightservice file and some other stuff none of them worked. As a last resort I looked online for similar devices and I tool begonia as a test, and it works flawlessly.

Even though it sets brightness to 2074, I tried manually changing it to 4095 with no difference at all.

I'll update the magisk module I made to use begonia's lightservice instead once I'm done with testing.