LVDS display problem with kernel 3.14.28

[ivandrobyshevsk]

I'm trying to add support for LVDS display to i.MX6DL board running 3.14.28 kernel, but the picture is distorted. See attached photos for details (in boot screen photo dark areas are supposed to be solid black).

The same display works fine with kernel imx_4.1.15_2.0.0_ga, but unfortunately there's a requirement to make it work with 3.14.28 kernel.

I've used exactly the same relevant DT nodes from 4.1.15 kernel (attached in a fido_display.dts file).

What is strange: setting resolution to 1920x1080 (proper/desired resolution is 800x480) and enabling split mode fixes the picture (see fbtest_ok.JPG), but it doesn't fit the display.

Any suggestions as to where to look: missing commit(s) to one of IPU drivers, DT properties, etc?

Also what kind of setting mismatch could produce picture distortion we are observing?

Thanks!

[ivandrobyshevsk · Accepted solution]

For whatever reason, clock speed had to be set two times faster compared to kernel 4.1.15. With higher speed picture looks good again.

[igorpadykov]

Hi Ivan

one can check if recommended LDB Clock Switch Procedure was implemented as

recommended by EB821

https://www.nxp.com/docs/en/engineering-bulletin/EB821.pdf 

Also one can try official nxp bsps described on

https://www.nxp.com/support/developer-resources/run-time-software/i.mx-developer-resources/i.mx-6ser...

Best regards
igor
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