Flickering display backlight ASUS K501UQ

[Fullmoon]

Since installation I have some sort of flickering. It's not broken icons or lines or other graphical artifacts. It looks like backlight itself is flickering, or like AC frequency banding lines on photo. Minor and noticeable only on dark backgrounds on medium-low brightness, but still mildly infuriating.

I have changed display panel to a better one, but Windows does not have any flicker, so it's unlikely to be because of faulty hardware.

I had to inject EDID until 10.13.4 (black screen after sleep), but it didn't help with flickering.

Not sure if related, but I also have infamous broken Apple logo at boot (just like in this thread, for example). IntelGraphicsFixup is installed. Yes, I've checked Skylake intel glitch fix, but a) it's for 530, while I have 520, and b) I tried it anyway, and got black screen with ig-platform-id 19120000. Patch by itself didn't help.

What else could it be?

Debug info attached.

 

[RehabMan]

Since installation I have some sort of flickering. It's not broken icons or lines or other graphical artifacts. It looks like backlight itself is flickering, or like AC frequency banding lines on photo. Minor and noticeable only on dark backgrounds on medium-low brightness, but still mildly infuriating.

Attach sample photo that shows the image where flickering present.

 

[Fullmoon]

Attach sample photo that shows the image where flickering present.

That's part of the problem. It is so minor that most of the time I can see it only with peripheral vision. Here's what I managed to caught on camera. That's with sunlight as background lighting and on battery, so there shouldn't be any AC influence.

 

[RehabMan]

Here's what I managed to caught on camera.

I see nothing there... mostly a blank screen that doesn't even look like macOS is running.

 

[Fullmoon]

I see nothing there... mostly a blank screen that doesn't even look like macOS is running.

Well, yes, because I tried to get dark background without anything else.

Ok, I tried to get another one. This time in complete darkness and with some macOS interface. Here. Hmm, now it looks worse than it really is.

Maybe something is wrong with display frequency.

 

[RehabMan]

Well, yes, because I tried to get dark background without anything else.

Ok, I tried to get another one. This time in complete darkness and with some macOS interface. Here. Hmm, now it looks worse than it really is.

Maybe something is wrong with display frequency.

You might try different ig-platform-id values.

 

[Fullmoon]

You might try different ig-platform-id values.

Ok, I'll try. What are compatible values for HD 520? I'm using 19160000, and, I think, 191b0000 is another. Are there others?

 

[RehabMan]

Ok, I'll try. What are compatible values for HD 520? I'm using 19160000, and, I think, 191b0000 is another. Are there others?

This is how you obtain all ig-platform-id values for SKL.

Install Hex Fiend.
In Terminal:

open -a "Hex Fiend" /System/Library/Extensions/AppleIntelSKLGraphicsFramebuffer.kext/Contents/MacOS/AppleIntelSKLGraphicsFramebuffer

In Hex Fiend, search for a known ig-platform-id, for example, 0x19120000 is hex search for '00 00 12 19'
Each ig-platform-id is 184 bytes (in this kext and KBL).
It helps to expand the Hex Fiend window to 23 columns (need a big screen, 184/4/2=23), because then you can see each ig-platform-id lined up vertically (every other row).
You will find the table starts with 0x191e0000 and the last is 0x19260007. The 0xFFFFFFFF signifies the end of table.

 

[Fullmoon]

Ok, I'll see if this leads anywhere. For now I noticed that at full brightness there is no flicker at all. I suspect that maybe something in SSDT-PNLF is wrong.

 

[RehabMan]

Ok, I'll see if this leads anywhere. For now I noticed that at full brightness there is no flicker at all. I suspect that maybe something in SSDT-PNLF is wrong.

Make sure you read the comments in SSDT-PNLF and the options you can set in SSDT-RMCF carefully.