Failed to start Load/Save Screen Backlight

[WLeun.3]

Hi everyone,

I have encounter the following error when booting the stm32mp157f-dk2

Starting Load/Save Screen …of backlight:5a000000.dsi.0...
[FAILED] Failed to start Load/Save …s of backlight:5a000000.dsi.0.
See 'systemctl status systemd-backlight…ht:5a000000.dsi.0.service' for details.

the 'systemctl status systemd-backlight@5a000000' give me the following

* systemd-backlight@5a000000.service - Load/Save Screen Backlight Brightness of
5a000000
 
Loaded: loaded (/lib/systemd/system/systemd-backlight@.service; static; vendor preset: disabled)
Active: inactive (dead)
Docs: man:systemd-backlight@.service(8)

The screen is able to display the splash image during uboot, so I assume the hardware is OK. When calling a GUI application, it fail and report error as 'Could not initialize egl display'

Any ideas?

[Olivier GALLIEN]

Hi @WLeun.3​ ,

 'Could not initialize egl display'

This trace let me think you are not using default Starter Package with Weston.

Could you please clarify your context ?

What image are you using? Ecosystem version ?

Thanks

Olivier

[WLeun.3]

​Hi Olivier,

'This trace let me think you are not using default Starter Package with Weston.'

Yes, I am not using the default starter package.

'What image are you using?'

It is a custom image, with meta-st-stm32mp layer as BSP.

'Ecosystem version ?'

I am not sure if this mean the yocto version, if yes I am using dunfell.

Actually my question is on the backlight error. I would like to know under what condition will it fail and how should I debug it, in particular the vendor preset column should be enabled instead of disabled. Honestly I am not sure whether this is a generic linux question or something related to the board.

Sorry if the last paragraph have confused you. All I want to emphasize on that paragraph is that the hardware is OK and correct device tree(stm32mp157-dk2.dtb) is loaded.

Regards

Leung

[Kevin HUBER]

Hello @WLeun.3​ ,

Can I have your complete log please.

Do you have another error related to weston wayland?

[FAILED] Failed to start Weston Wayland Compositor.

In general the backlight or westo wayland error are because of an error in the DTS file.

Please Can you send me the traces if you run the command:

modetest -M stm

as explained here:

https://wiki.st.com/stm32mpu/wiki/DRM_KMS_overview#Show_display_overall_status

And then send me your stm32mp157f-dk2.dts and the stm32mpxx-dkx.dtsi please.

Regards,

Kévin

[WLeun.3]

Hi Kévin,

Thanks for your help!

'Do you have another error related to weston wayland?'

No, the backlight error is the only error I got.

I am able to display the test image as

modetest -M stm -s 35@40:480x800

but the backlight error still persist.

Regards,

Leung

[Kevin HUBER · Accepted solution]

Hello @WLeun.3​ ,

Your DTS configuration for DSI/LTDC devices seems correct and since you are able to use modetest, it means that your DRM/KMS test tool is working too.

As you said your are not using the default image with Weston, but to use the screen you have to use an image with a framework to manage the screen.

In our default distribution st-image-weston, we use wayland/weston.

When this package is enabled.

You must have in your log at least these traces:

         Starting Weston Wayland Compositor (on tty7)...

and

[  OK  ] Started Weston Wayland Compositor (on tty7).

Otherwise, you will not have your screen usable.

In a normal case, just after the creation of system backlight, you have system weston

[  OK  ] Created slice system-systemd\x2dbacklight.slice.
[  OK  ] Created slice system-weston.slice.

Did you removed weston support on purpose? You talked about eglfs before, if you want to use eglfs on purpose, please have a look at:

https://wiki.st.com/stm32mpu/wiki/How_to_build_and_use_an_SDK_for_QT#QT_image_and_SDK_with_EGLFS

And look at this DISTRO to verify that you correctly built all the needed package:

layers/meta-st/meta-st-openstlinux/conf/distro/openstlinux-eglfs.conf

I'm not use to EGLFS, but if you need more help, I will need your manifest file to see the packages that you built.

In the st-image-weston, you can find it in: <build-directory>/tmp-glibc/deploy/images/stm32mp1/st-image-weston-openstlinux-weston-stm32mp1.manifest

Its name is <your-image-name>.manifest.

Regards,

Kévin

[WLeun.3]

Hi Kévin,

Sorry for my late reply.

After testing with the openstlinux-eglfs distribution and the qt-example image, we think that it might be good enough for our application(although it is not perfect). At this point we will just stick with it and proceed our development to test other component.

Thanks for your help again.

​Leung