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T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

T430 and later, plus T530 and later series specific matters only
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Reagle
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T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

#1 Post by Reagle » Sat May 02, 2020 6:58 pm

Had this machine upgraded in 2016 (viewtopic.php?f=68&t=122281&p=789484#p789484) and it's been mostly fine, but every so often screen would just go blank after windows starts. If I connect external monitor it would come back and run on the LCD at the wrong resolution. I started poking at it and realized the B140HAN01.2 panel I put in did not have Lenovo specific info in its EDID so it runs generic Windows 10 drivers and occasionally get miss-configured.
After much googling I found out that EDID data can be rewritten under Linux to that of Lenovo version of the same panel. Trouble is I am not able to find the EDID chip on any i2C buses.
This is using Ubunutu 20.04 live image,
get-edid scans all buses and finds no EDID at all
i2cdetect sees i915 gmbus panel on I2c-3 bus
edid-rw does not see the chip there

Any idea why none of tehse tools can see the panel? Somehow in windows under moninfo I can get most of what's in it
http://kuzyatech.com
T490 20N2CTO1WW
T440P 20AWS0RQ00 (aka FrankenPad)
T420 4236-J22
X200 7454-95U
X31 2672-C2U
X31 2672-N7U
X31 2672-B1U (parts)

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Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

#2 Post by RealBlackStuff » Sun May 03, 2020 1:49 am

Not all LCDs have an EDID-chip.
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Reagle
Posts: 14
Joined: Fri Apr 10, 2009 1:39 pm
Location: Rochester, NY
Contact:

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

#3 Post by Reagle » Sun May 03, 2020 7:34 am

How is the system detecting the panel though? It knows enough to say it' AUO and use the correct timing most of the time.
Or am i chasing the wrong issue and something else makes windows 10 confused with this?
http://kuzyatech.com
T490 20N2CTO1WW
T440P 20AWS0RQ00 (aka FrankenPad)
T420 4236-J22
X200 7454-95U
X31 2672-C2U
X31 2672-N7U
X31 2672-B1U (parts)

Reagle
Posts: 14
Joined: Fri Apr 10, 2009 1:39 pm
Location: Rochester, NY
Contact:

Re: T440P with transplanted 1080P IPS panel- windows screen blanking, EDID data?

#4 Post by Reagle » Sun May 03, 2020 10:41 pm

Never mind, I found the answer- these are eDP panels, so they do not expose EDID data externally over I2C like older LVDS panels did.
They use an Aux channel of eDP to send all this data. So the EDID eeprom is still there but is accessed differently.
I suppose reflashing it directly might be an option.
See http://www.vesa.org/wp-content/uploads ... 10-v3.pdf pages 8 and 10
http://kuzyatech.com
T490 20N2CTO1WW
T440P 20AWS0RQ00 (aka FrankenPad)
T420 4236-J22
X200 7454-95U
X31 2672-C2U
X31 2672-N7U
X31 2672-B1U (parts)

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