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Linux: Mcasp clock synchronization

Tool/software: Linux

Hii ,

I am trying to achieve media clock synchronization between two jacinto 6 EVM boards with ti-glsdk_dra7xx-evm_7_03_00_03 kernel image . For that I want the talker to get timestamps of the sampling clock from one node ,To achieve this I have planned of using CPTS driver for getting timestamps . In other EVM node I have to create a sampling clock with particular frequency and I have to align the rising edges of the clock from user space . My queries are as follows:

1. Whether I can achieve the synchronization of the two evm mcasp clocks?.

2. If possible How can I route the mcasp clock to CPTS? and how can I get the timestamps in user space ?.

3. I want to access the PLL used by Mcasp clock from user space. Is there any available sys calls for that purpose or I have to do any changes in the kernel source code?

  • Hi Kumar,

    I'm not an MCASP expert, but I'm wondering  - isn't it enough to configure one MCASP as clock source and the other as clock sink? MCASP chapter in TRM describes many of the clock sync scenarios for MCASP.

    Regards,

    Stan

  • Kumar,

    Re "I want to access the PLL used by Mcasp clock from user space" - It's not possible to access the PLL from userspace. For debugging purposes one can use tools like omapconf to access any register, but I imagine that's not the context of your question.

    What's the reason behind trying to access the DPLL? If the intention is to adjust its frequency to match the other EVM node, then I'm afraid it's not possible. I believe there are exceptions, but generally speaking the DPLLs can't be changed on-the-fly.