[Librem-5-dev] Bringing up the lcd

[Andy Green]

On 06/03/2019 15:53, Guido Günther wrote:
> Hi,
> On Wed, Mar 06, 2019 at 11:39:14AM +0800, Andy Green via Librem-5-dev wrote:
>> Hi -
>>
>> I'm running
>>
>> Linux version 4.18.11-00385-g997d1697a591
>>
>> which is HEAD from March 5th... how to bring up the LCD + backlight from the
>> commandline?
>>
>> Eg,
>>
>> # echo 1 > /sys/class/backlight/backlight_dsi/bl_power
>> # echo 100 > /sys/class/backlight/backlight_dsi/brightness
>>
>> doesn't buy me anything.
>>
>> # chvt 2
>>
>> shows it spawned an agetty on the VT, but nothing displayed.
>>
>> /sbin/agetty -o -p -- \u --noclear tty2 linux
>>
>> Is it written somewhere how to bring up the display with current
>> kernels?
> 
> If you already flashed a new image¹ (just updating the kernel is not

Thanks... I hadn't... I had just upgraded all the packages and tried the 
new kernel. [1]

FYI on Fedora, I had to install the following to build uuu (AFAIK it's 
not packaged for Fedora).

$ sudo dnf install libusb-devel libzip-devel bzip2-devel libstdc++-static

The names for the python pieces of the image download script turned out 
to be the same on Fedora

$ sudo dnf install python3-jenkins python3-tqdm python3-yaml

> enough since you also need to update device tree) and the backlight

My dtb is in /boot and was also updated to match the kernel image.

But on the factory image, the kernel commandline forces related stuff

video=HDMI-A-1:1920x1080-32 at 60

via U-Boot environment. [2]

> doesn't even turn on try reseating the ribbon cable². In case of a
> complete blank display that's the number one cause.

I guess that's talking about J1202, eyeballing it, it looks straight 
within a degree or two.

The problem was the flat cable must be pushed into the receptacle.  It 
was only vaguly going in the apeture.

The white line on the cable must be obscured by the hinged lid closing 
on it.  After I pushed it in and closed the lid, it worked 
immediately.... very cool :-)

-Andy

[1] I realize it's early, pre-release days but it'll be a huge advantage 
over Android to be able to completely update by packaging "from the 
start".  So I hope "reimage" goes away soon as a prescription for updating.

Being able to reimage from scratch is obviously important, but it should 
only be needed for debricking or something like repartitioning.

[2] .. if that's why it needs a complete reimage (the kernel commandline 
after the update no longer has video= ) it's another sign that the 
U-Boot environment is a bit of a fingertrap when it comes to maintaining it.

> Cheers,
>   -- Guido
> 
> 1: https://developer.puri.sm/Librem5/Development_Environment/Boards/imx8.html#flashing-emmc
> 2; https://source.puri.sm/Librem5/developer.puri.sm/issues/82
> 
>>
>> -Andy
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