[coreboot] Solving zilogpnz's backlight problem at Lenovo G505s

Vladimir quickcracktime at gmail.com
Sat May 2 19:29:03 CEST 2015


Try using vgabios of your Radeon HD 8650G ( " 1002,990b " graphic device of
A10-5750M APU ) during coreboot compilation. According to G505s wiki page,
currently AtomBIOS blob is needed for onboard VGA, but maybe its also
needed for your working backlight?

I retrieved my vgabios via Linux kernel 3.19 using this method -
http://www.coreboot.org/VGA_support#Retrieval_via_Linux_kernel  .Then I
downloaded latest sources of SeaBIOS & Coreboot, and build Coreboot using
compiled SeaBIOS payload as well as vgabios file. My configuration is a bit
similar to this one -
http://www.coreboot.org/Supported_Motherboards#lenovo.2Fg505s - although
some options were added and some removed since a time of that build.

In my understanding, vgabios needs to be extracted from a running machine.
So just in case if your G505s is in bricked state and you can't run it for
extraction of vgabios, I am sending it to you in attachments of this letter!

However I need to mention one interesting thing: *after *my laptop started
running coreboot, what I retrieve via Linux kernel is now slightly
different -- if to compare with what I used to retrieve *before *, while my
laptop was still running a proprietary BIOS. And I have flashed coreboot
rom into BIOS chip with file verification , so that doesn't seem to be a
"bad flashing" case. Looks like Coreboot does not load a vgabios ROM inside
it AS-IS, and instead modifies it slightly while loading...

So here are two bios files for you (could use any of them, maybe "before"
one like I did)
vgabios_before.bin - SHA1 checksum: e4d320eb278b0118c46e2e470e7154b12c41966d
vgabios__after.bin - SHA1 checksum: a9e2ed569bbaaea283b5380a5f6c44fc4efc3da4

And here is a report about 3 bytes difference between them -
http://www.diffnow.com/?report=2kwq3

P.S. What if your backlight problem could be related to manufacturer/model
of LCD panel? For the reference, my panel is Samsung LTN156AT30L01 ( SDC
Model 4652 ) which is working perfectly

On 4 April 2015 at 13:08, Vladimir <quickcracktime at gmail.com> wrote:
> Very sorry to hear that your LCD backlight problem is not resolved yet!
> Are you confident that LCD backlight is not faulty, and have you tried
> reinstalling coreboot?
>
> If answer for both questions is "yes", then you could try these two
advices:
>
> 1) Redownload a source code of coreboot from github, compile it and flash
> again to your G505s.
> Since your last try - at the end of January - there were 5 commits to
> "coreboot/src/mainboard/lenovo/g505s" branch,
> and also some commits to the common branches, changes that affect all the
> mainboards supported by coreboot.
> Maybe your issue will be resolved if you would try coreboot again, with
> latest sources!
>
> 2) If 1st advice doesn't work, you could open
> "coreboot/src/mainboard/lenovo/g505s/buildOpts.c" file
> (which is the only file from G505s branch that has a reference to "LCD")
> Go to line 158, try to change the "#define
BLDCFG_CFG_LCD_BACK_LIGHT_CONTROL
> 200" parameter.
> Default value seems to be 200 for most platforms, but you could try
setting
> it to 0. Then compile & flash again
>
> === Any advices from experienced coreboot members would be very welcome!
===
>
> On 3 April 2015 at 17:46, 1 1 <zilogpnz at gmail.com> wrote:
>>
>> No. I not solved this problem.
>>
>> 2015-04-03 17:08 GMT+04:00 Vladimir <quickcracktime at gmail.com>:
>>>
>>> > On Mon Jan 26 13:07:42 CET 2015 zilogpnz wrote:
>>> >> I'm trying to run Coreboot on Lenovo G505s and have a problem:
>>> >> - backlight of LCD is not turn on. But on the external LCD (by CRT
>>> >> connector) is all good.
>>> >>
>>> >> Could you help me with a solution to this problem?
>>>
>>>
>>> Sorry for such a long reply, but what is a current status of this
>>> problem?
>>> Have you resolved the LCD backlight problem with your G505s - and, if
>>> yes, how?
>>
>>
>
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