LVDS - Kernel 5.4 - linux-imx

[ycardaillac]

Hi there,

I'm updating a custom imx6d board from kernel 4.x to kernel 5.4 from your main yocto recipes.

I'm having a hard time integrating my lvds screen. I can't find what is my dts error, I'm basing the integration on your imx6qdl-sabreauto devicetree. And it's also based on my older kernel device tree.

Basically my board has two screens, one in lcd which is working (eventhough I had to back port the lcd driver), and the other one is in lvds channel 1.

Do you see anything missing that might explain why my configuration doesn't work, I know that this is not a hardware problem since the scerens are working with my older kernel+dts.

Find in this pastebin the relevant part of my dts: https://pastebin.com/Yai8Xqng

For the sake of completeness here is my complete devicetree, just in case something might be missing: https://pastebin.com/m15BduAd

Best regards,

Yann

[Zhiming_Liu]

Can you also compare the lvds boot log between kernel 4.x and kernel 5.4?

This should be a compatibility issue with certain APIs after the kernel upgrade.

[ycardaillac]

Hi Qmiller,

Actually I can't see much difference between the two versions, both
[ 0.416328] mxc_sdc_fb fb@0: registered mxc display driver ldb
[ 0.563388] mxc_sdc_fb fb@2: registered mxc display driver lcd

The lcd side however did work as expected, I'm wondering what do you mean by kernel API change? Shouldn't it work directly since the driver comes from your repos?

Best regards,

Yann

[Zhiming_Liu]

Hi @ycardaillac 

You can dump the clock setting and registers about lvds display and then compare the difference between L 4.14 and L5.4

[ycardaillac]

oh, ok nice good idea, how would you do that?

I think I could use devmem2 to do that, what register should I look at? What are the relevant one?