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iMX6 - how to change DDR PFD frequency

Question asked by nickbedbury on Feb 5, 2019
Latest reply on Mar 25, 2019 by igorpadykov

I'd like to change the frequency of the iMX6UL DDR clock via the PFD divider. 

 

I've been able to change register "CCM_ANALOG_PFD_528n" field "PFD2_FRAC" in uboot and see clock adjust accordingly.  However, after changing the fractional divider value, the "PFD2_STABLE" bit never shows stable (1), it stays (0).

 

What is the proper sequence of register writes so that the PFD is stable after editing?

 

I've read through EB790 (https://www.nxp.com/docs/en/engineering-bulletin/EB790.pdf ) but it does not seem to give an example of changing the frequency divider, just disabling or bypassing altogether.

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