Spread spectrum on DSI output of Colibri iMX8X with and without DSI-to-HDMI adapter

Dear Community,

after rebuilding SCFW enabling spread spectrum on DC0 PPL0 and PLL1 as explained in “User Guide About Spread Spectrum Support for i.MX 8QuadMax and i.MX 8QuadXPlus Display, User Guide, Rev.2.1, 05/2020” by NXP and deploying it as a boot container to the Colibri iMX8X, I cannot measure the spread spectrum clock on clock signals, neither on DSI output on Colibri X2 connector nor on HDMI clock after the LT8912B output of the DSI-to-HDMI adapter.

Is it possible that some further changes are needed in device tree or in other parameters? Or maybe the DC0 PPL settings are applied only to LVDS and not to DSI output even if the are from the same “combo” PHY?

Even if LT8912B clock output on HDMI side is independent from the DSI clock input, I would expect to see at least the DSI clock oscillation. Unfortunately I cannot find user manual of LT8192B online.

Thank you for the attention and best regards,


Greetings @ldvp!

Can you please try these steps on a newer image? I see that you’re using TorizonCore 5.1.0, but I highly suggest you to try this on TorizonCore (or BSP) 5.2.0. or even on the newer 5.3.0 nightlies.

Hi @gustavo.tx! Thank you for the suggestion, I will soon upgrade to latest version, rebuild the SCFW in boot-container and re-measure. According to the commit log, with respect to the one I used (1f184f1), there are indedded changes on RAM clock, NXP SDK and UART logging.

On the other hand, I wonder why Toradex does not enable spread spectrum by default on LVDS output clock in i.MX-System-Controller-Firmware.git. If video performance is the same but radiated emission peak is reduced, I think it would be beneficial to all users.

Hi @ldvp!

Nice, let me know about your results.

I also brought your suggestion of enabling SS by default on the LVDS output clock to the BSP team. I’ll let you know if they provide any comments on that also.

Hello, Gustavo is there something new.

best Regards,


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hi @gustavo.tx

Will Toradex do a version of SCFW with Spread Spectrum enabled?

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Hello Dmray,

I forwarded this to the development team.

but I can not if and when they will add this and some dokumentation.

Best Regrads