AM625: Enable flicker free screen from kernel simple-framebuffer to panel-simple

Gireesh Hiremath

Part Number: AM625
Other Parts Discussed in Thread: SK-LCD1

Hi,

We are working on parallel display bring up for custom board based on am625.

Able to enable splash screen from spl -> u-boot -> simple-framebuffer(kernel with reserved memory)-> panel-simple(actual kernel driver). we seen negligible flicker from spl->u-boot and no flicker form u-boot -> simple-framebuffer, but seeing considerable flicker from simple-framebuffer -> panel-simple. It may be due to complete restart of display subsystem at kernel, is there any option to null or reduce flicker at stage simple-framebuffer -> panel-simple ?

Thanks,

Gireesh Hiremath

6 days ago

0 Divyansh Mittal 3 days ago

TI__Genius 14020 points

Hi Gireesh,
I am assuming you already have the 'simple-framebuffer' related changes as per the default TI-SDK in your setup (https://software-dl.ti.com/processor-sdk-linux/esd/AM62PX/latest/exports/docs/linux/Foundational_Components/U-Boot/UG-Splash-Screen.html#flicker-free-display-across-boot-stages-and-linux-kernel).

Can you please share the output of the following:
zcat /proc/config.gz | grep CONFIG_DRM_FBDEV_EMULATION

If this is set to 'y', can you please try unsetting in the defconfig and retry? For more details:
https://software-dl.ti.com/processor-sdk-linux/esd/AM62PX/latest/exports/docs/linux/Foundational_Components/U-Boot/UG-Splash-Screen.html#flicker-free-and-persistent-display-until-display-server

0 Gireesh Hiremath 2 days ago in reply to Divyansh Mittal

Intellectual 445 points

Hi Divyansh,

I tried by disabling CONFIG_DRM_FBDEV_EMULATION, it is stopping kernel splash screen and also started getting color loop on screen ( entire screen blue for one second - then green one second - red-white-black...) and also not transferring control to application.

Please give suggestion.

Regards,

Gireesh Hiremath

0 Divyansh Mittal 2 days ago in reply to Gireesh Hiremath

TI__Genius 14020 points

Hi Gireesh,
Seems there are some changes in your custom setup. If you have a TI EVM, would recommend checking this out on that. What you mentioned is not expected and not seen at my end.

0 Gireesh Hiremath 1 day ago in reply to Divyansh Mittal

Intellectual 445 points

Hi Divyansh,

Ok, we have TI EVM but not the same display, any alternative to validate?

Regards,

Gireesh Hiremath

0 Divyansh Mittal 1 day ago in reply to Gireesh Hiremath

TI__Genius 14020 points

Hi Gireesh,
Which display are you using, is it not directly compatible with the TI EVM, typically you can check this on SK-LCD1 OLDI panel out-of-the box, but you can use the compatible for your OLDI panel if the pins are directly compatible.

0 Gireesh Hiremath 1 day ago in reply to Divyansh Mittal

Intellectual 445 points

Hi Divyansh,

We are using parallel display, it is compatible with OLDI pins. disabling CONFIG_DRM_FBDEV_EMULATION will not work for parallel display?

Regards,

Gireesh Hiremath

0 Divyansh Mittal 23 hours ago in reply to Gireesh Hiremath

TI__Genius 14020 points

Hi Gireesh,
I am slightly confused on which interface you are using. Current U-Boot only supports dual-link OLDI based splash, while the kernel supports both OLDI and DPI via separate Video Ports.
This flicker free transition on current SDK will be effective when using OLDI panel transitioning from U-Boot to Kernel.
Are you using a DPI panel or OLDI panel?

0 Gireesh Hiremath 17 hours ago in reply to Divyansh Mittal

Intellectual 445 points

Hi,

I am using DPI panel.

Regards,

Gireesh

0 Divyansh Mittal 18 minutes ago in reply to Gireesh Hiremath

TI__Genius 14020 points

How are you getting a splash screen on DPI? Have you made custom changes on the U-Boot side?

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AM625: Enable flicker free screen from kernel simple-framebuffer to panel-simple