Linux/AM5726: DSP clock configuration

Allen35065

Part Number: AM5726

Tool/software: Linux

Hi expert,

Customer want to use DSP core in AM5726 at 600MHz to save power. They set DSP to 600M in uboot but after kernel boot up DSP clock was fixed to 750M.

Could you please tell me where to modify initial DSP clock in kernel?

Thank you.

Regards,

Allen

over 8 years ago

0 Yordan Kovachev over 8 years ago

TI__Guru**** 161600 points

I am looking into this. I will post my findings here.

Best Regards,
Yordan

0 Pavel Botev over 8 years ago

TI__Guru**** 170625 points

Hi Allen,

Do you use AM572x TI PSDK v4.00?

From what I understand you have modified bit-field CM_CLKSEL_DPLL_DSP[18:8] DPLL_MULT in u-boot code base? In which u-boot file exactly?

You can interrupt the boot process, enter into the u-boot prompt and check (with md command) if this DPLL_MULT value is still what you expect, thus will be sure that u-boot do not overwrite it.

Regards,
Pavel

0 Yordan Kovachev over 8 years ago in reply to Pavel Botev

TI__Guru**** 161600 points

In addition to Pavel's reply, this is done in DSP firmware, not in linux kernel. This is why your u-boot configurations are overwritten once the kernel takes over & loads dsp firmware.

Also the following guides will be useful in your case:
processors.wiki.ti.com/.../Processor_SDK_Linux_Automotive_FAQ

The automotive processor SDK & Processor SDK use almost the same kenrel & u-boot sources, so mentioned files should match.

Best Regards,
Yordan

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Linux/AM5726: DSP clock configuration