imx7s DDR frequency scaling

tmeyer — Fri, 16 Jun 2017 14:25:19 GMT

I have linux-fslc 4.1-1.0.x-imx running on my imx7 target. The busfreq driver is working as I can see the DDR freequency change between 24 and 533 MHz. However, the busfreq driver seems to be missing support for various other frequencies.

In the dts file changing fsl,max_ddr_freq = <200000000> in "fsl,imx_busfreq", for example, hos no effect. I traced through the code and ended at ddr3_freq_imx7d.S. This driver (unless I miss-read it) only handles 24, 100, & everything above 100 gets set to 533. I looked through th imx6 variant of this file and it seemed to have more support for the input clock frequency.

Am I understanding this correctly? Is there a new version of this driver that supports other frequencies? Or do I change the ddr3_freq_imx7d.S for my desired clock source and frequency?

Thanks in advance,

Tim

Re: imx7s DDR frequency scaling

igorpadykov — Fri, 16 Jun 2017 23:20:15 GMT

Hi Tim

yes this is correct understanding, supported limited number of frequency

setpoints, please check description of bus frequency driver

in sect.24.1.2 Software Operation attached Linux Manual.

Best regards
igor
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imx7s DDR frequency scaling

Re: imx7s DDR frequency scaling