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Dell Latitude 5491: HDMI not working


tidelust

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Greetings everyone, so I tried many ig-platform-id to make either my HDMI port or DP (Type-C) works on my Dell Latitude 5491 running i7-8850H. As far as I know the recommended id is 3EA50009 which falls to these arrangements:image.png.549c4a9c8d6048178ac89f95fd4a162a.png

The only problem is I couldn't figure out on how to make the HDMI port work, while the connector isn't patched to HDMI yet it supposed to output video signal but not audio afaik, but in this case nothing appears on my monitor.
I didn't turn off any HDMI or DP related settings in the BIOS setup. Tried USB-C to HDMI, and direct HDMI port but it still outputs nothing.
I attached my EFI (without unnecessary kexts, and so on that's unrelated to this problem) and IOReg dump in one zipped file, helps are appreciated. Thank you in advance.

Archive.zip

Edited by tidelust
Grammar mistakes... yet again :D
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Hello, you're using the recommended CFL framebuffer layout for sure. I've noticed 2 things:

  1. your IOReg shows MBP15,1 in use, yet your OC config uses MBP15,3 SMBIOS; there is discrepancy here.
  2. you patch iGPU fbmem and stolenmem with recommended values but this can occasionally impact HDMI output.

If you can patch your BIOS through the documented GRUB process to set DVMT to 64MB (or higher), you could get rid of the fbmem/stolenmem patches.

Did you try the igfxonln=1 boot arg? It's sometimes required to get HDMI working alongside the built-in screen.

Then, of course, no harm in experimenting patching con1 and/or con2 to HDMI type. Yes, it's usually only required for HDMI audio but, on occasion, it can fix issues with HDMI video issues.

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1. I actually tried to change the SMBIOS model in the EFI config on another USB stick just so I thought it'll just work, but I realized I've mixed the IOReg file with one another. I attached the correct IOReg, sorry for the confusion.Rin's MacBook Pro.ioreg.zip

2. I've never thought this will impact HDMI... Is there a guide to patch DVMT to 64MB? 

 

I will edit this reply once I tried igfxonln=1 boot-arg, and lastly for patching con1 and/or con2 to HDMI type I've done that before but still it doesn't output anything.

EDIT: Tried igfxonln=1 boot-arg still doesn't work.

This kind of confuses me too, when I checked Windows does: "Dedicated Video Memory" simply means DVMT? If that's so then I can safely remove framebuffer-fbmem and framebuffer-stolenmem altogether, right?

Screenshot 2024-02-19 235054.png

Edited by tidelust
Tried adding igfxonln=1 to the boot-arg, removing framebuffer-stolenmem and framebuffer-fbmem properties, and attaching screenshot
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Ok, then you have to experiment with patching of connectors: index, BusID, possibly Pipe and highly likely Flags.

Did you try to monitor your iGPU connectors real-time in IOReg as you plug/unplug an HDMI cable?

 

With regards to DVMT, if you try and boot without fbmem and stolenmem patches, do so on a bootable USB Key so that you don't mess out your bootable installation on the SSD. Or vice versa; if you modify the SSD on the EFI partition of your SSD, make sure to have a bootable USB key as backup.

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On 2/20/2024 at 6:19 PM, Hervé said:

Did you try to monitor your iGPU connectors real-time in IOReg as you plug/unplug an HDMI cable?

Yeah, I've tried everything except changing flags... For some reason the screen on my laptop went blank for a while when I go to System Settings -> Display and then clicking on "Detect Displays".

By looking at my laptop's IOReg, yes there are two other connectors besides the main display, and both AppleIntelFramebuffer 1 and 2 was assigned to DP by default. Tried using WhateverGreen debug didn't shed any lights to the problem, it remains undetected in both system.log (according to WhateverGreen's docs) and IOReg.

 

I'm sure my HDMI works properly because I have Windows to test it out.

But just for kicks and giggles is there a way to determine what Windows actually recognize/read every display out port(s)? Like the Index, BusID, and flags?

 

Sorry for late reply, I'm catching up on uni things.

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I see, so the only way to find out is to cycle around BusIDs in the end... Last time I tried the same ig-platform-id but without the force-online property in DeviceProperties (I believe it's the same as igfxonln=1 in boot-args), and it seems like the screen didn't refresh when I click on "Detect Displays" so maybe I should give another shot of cycling around BusIDs with that property included?

 

For changing flags, I don't really understand how flags actually work. After some extent searches it didn't yield any kind of results that I'm looking for. Pipe number is about the same... Now I'm really confused. 😭

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Well, this kinda drive me nuts.

The Type-C HDMI seems to almost work because when I click on Detect Displays the screen refreshes and when I unplug the HDMI and did the same thing, the screen remains on.

 

Currently cycling around con1 with these properties (Port, BusID, and Pipe), trying to cycle around BusIDs first and then Pipe numbers:

Quote

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