PROCESSOR-SDK-AM57X: DM Timer support on CPTS driver is missing on TI SDK 9

Hello Naiara,

I am checking in with our dev team and will respond accordingly.

-Josue

I was investigating a bit more about this topic, in the SDK 9.03 documentation you describe the possibility of using the phc2pwm program within linuxptp to generate the PPS signal from a DM timer. A specific DTB with PPS generation support is also referenced, but I can't find it on installed SDK 9.03: am571x-idk-pps.dtb.

And then run in console:

Processor SDK Linux for AM57X - CPTS

If I would like DM Timer 13 to generate PPS signal when synchronizing through PTP over GMAC, shall I only include the following node in DTB?

pwm13: dmtimer-pwm {
        compatible = "ti,omap-dmtimer-pwm";
        ti,timers = <&timer13>;
        #pwm-cells = <3>;
};

And then run in console:

 # phc2pwm -h
usage: phc2pwm [options]

-p [dev]       Clock device to use
-e [id]        PTP index for event/trigger
-w [id]        PWM chip device id
-c [id]        PWM channel id from PWM chip
-l [num]       set the logging level to 'num'
-h             prints this message and exits

 # ./phc2pwm -p /dev/ptp0 -c 0 -e 0 -w 0

Are these arguments correct? Is there something else missing?

Thank you Naiara,

I am still awaiting input from our Dev team. Thank you for your patience.

You are correct. I do not believe the PPS overlay was included in the 9.3 release. The only place i see it is in the 5.10 kernel which is 8.02 SDK. I also think it is available in the older release. 

My guess this is not supported based on the note on that documentation shared: 

"CPTS module in AM335x, AM437x and AM57xx SoCs did not support generating a PTP clock synchronized Pulse-Per-Second (PPS) signal. "

And the suggestion is merely some direction on how to enable it if needed. I will wait or the Dev teams feedback.

-Josue

Naiara,

The dev team has confirmed that there was no validation nor testing done for this functionality on the 9.3 SDK. Therefore it is not officially supported.

-Josue

Thanks Josue for the rapid response.

We are highly concerned about this issue. How could we integrate PTP protocol on AM57x with 9.3 SDK without the DM timer support from CPTS? Is it planned to manage from linuxptp stack through a PWM node as you reported in the documentation? Should we declare support of HW_TS_PUSH inputs in DT?

I looked for cpts-ext-ts-inputs property within TI Ethernet driver folder, but I found that property to be parsed from DT only in am65-cpts.c file for AM65 boards. Maybe a patch could be applied to cpts.c file employed in our system to give support to that property and make it configurable in the DT? 

Could you tell me from which release of linuxptp stack on is available the PWM based PPS generation? Which branch and commit of processor-sdk/linuxptp/ repo should we employed in that case?

Regards,

Naiara

Naiara,

Will have to check with our dev team again. The documentation clearly states that PTP in AM57 is not supported. So for now, this is a new feature request.

Josue Zamitiz-Ayala said:

"CPTS module in AM335x, AM437x and AM57xx SoCs did not support generating a PTP clock synchronized Pulse-Per-Second (PPS) signal. "

https://software-dl.ti.com/processor-sdk-linux/esd/AM57X/09_03_06_05/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW.html#:~:text=CPTS%20module%20in%20AM335x%2C%20AM437x%20and%20AM57xx%20SoCs%20did%20not%20support%20generating%20a%20PTP%20clock%20synchronized%20Pulse%2DPer%2DSecond%20(PPS)%20signal.

Again, thank you for your patience.

-Josue

Hi Josue,

Please, check PTP support on AM57xx as soon as possible with your dev team. This is highly important in our system to provide PTP.

I appreciate your clarity, but I am not sure about PTP not being supported. What documentation says is that CPTS module does not support PPS signal generation, it never had support for that in previous releases of AM57xx SDK. This support and the corresponding HW timestamping support was provided by a patch to the driver which employed a DM timer to include this feature. This patch is missing in the SDK 9.3 release.

Otherwise, in SDK 9.3 documentation, this support is suggested to be achieved by configuring one of the DM timers that are connected to CPTS module in PWM mode, but the referenced example DT files were not found:

https://software-dl.ti.com/processor-sdk-linux/esd/AM57X/09_03_06_05/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW.html#:~:text=It%20is%20required%20to%20boot%20kernel%20using%20pps%20specfic%20dtb.%20Like%20for%20am571%2Didk%2C%20am571x%2Didk%2Dpps.dtb%20should%20be%20used.

Naiara

Naiara,

I understand your ask and urgency. The dev team is already looking into it, as i mentioned above. You are correct that there is no documentation for it not being supported other then the lack of patch and the confirmation given above.

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1465438/processor-sdk-am57x-dm-timer-support-on-cpts-driver-is-missing-on-ti-sdk-9/5629343#5629343

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1465438/processor-sdk-am57x-dm-timer-support-on-cpts-driver-is-missing-on-ti-sdk-9/5627532#5627532

-Josue