AM625: Timestampe externel events via CPTS

Hello Zain,

Please provide additional information.

1) What version of Linux SDK are you using?

2) What changes did you make to the DTS files?

3) which pin / header are you attaching your input signal to?

4) How are you running tests from the software side?

At this point, I have not used testptp for general timestamping. Off the top of my head, I am not sure if it can be used in that way, or if it is specific to Ethernet PTP communication.

Regards,

Nick

Hello Nick,

• Version 09.02.01.10
• I added this to the DTS:

  • &timesync_router {
            status = "okay";
            pinctrl-names = "default";
            pinctrl-0 = <&cpsw_cpts>;
    
            cpsw_cpts: cpsw-cpts {
                    pinctrl-single,pins = <
                                 .
                                 .
                                 .
                            /* TS Push Pin [CP_GEMAC_CPTS0_HW1TSPUSH] in12 -> out12 [cpsw cpts hw1_push] */
                            K3_TS_OFFSET(10, 12)
                            >;
            };
    };
    
    

  • &main_pmx0 {
            
            .
            .
            .
            cpsw3g1_pins_default: cpsw3g1-default-pins {
                    pinctrl-single,pins = <
                            AM62X_IOPAD(0x01c0, PIN_INPUT, 1) /* (B13) SPI0_D0.CP_GEMAC_CPTS0_HW1TSPUSH */
                    >;
            };
    
    
    
    };
    

• I use the Synphony Board from Variscite. I used the J10. First i disbaled the spi interface for the resestive touch because i use the same CP_GEMAC_CPTS0_HW1TSPUSH pin and i don't use it at all.

  • &main_spi0 {
            status = "disable";
            pinctrl-names = "default";
            pinctrl-0 = <&main_spi0_pins_default>;
            ti,pindir-d0-out-d1-in = <1>;
    
            ads7846@0 {
    
                    status = "disable";
            };
    };
    
    

• I run testes using testptp tool with the following command;

  •     testptp -d /dev/ptp0 -e 10 -i 2   
    

    
    

Of course testptp is specific to PTP. I have the ptp0 interface allready and it works fine.

Do you any another tools to measure timestamping?

BR

Zain

Hello Zain,

Good question. I do not see any kernel drivers that make use of CPTS for timestamping outside of drivers/net/ethernet/ti. Give me a couple of days to ask around to see if there is any preexisting code that I am unaware of.

Can you tell me a bit more about your usecase?

We do support using ECAP to capture timestamps for sure. So that might be an easier solution for your usecase. See this thread for more:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1242640/am625-ecap/4766153#4766153

Regards,

Nick

Hi Nick,

do you have any new info?

In /sys/class/ptp/ptp0 i can'nt enable extts_enable. I get the following error:

root@am62x-var-som:~# echo 1 > /sys/class/ptp/ptp0/extts_enable 
-bash: echo: write error: Invalid argument

root@am62x-var-som:/sys/class/ptp/ptp0# cat extts_enable 
cat: extts_enable: Permission denied

Hello Nick,

I would like to use the HW-TS feature in CPTS to timestamp an external frequency. I have already successfully implemented eCAP, but discovered that timestamps only refer to a 32-bit counter. Therefore, the input event is timestamped based on the counter value and not, as with cpts, based on the system time. Of course, I can measure the current time for each timestamp. I don't want to do that because cpts's HW TS does it automatically and much more accurately than eCAP.

Hello Zain,

I have not played around with the extts_enable feature yet. It looks like you need to write the channel index, followed by a "1" to enable timestamps from that channel: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-ptp

Ok, so... what is each channel?

Looks like entry n_external_timestamps tells us how many external timestamp channels are offered. Off the top of my head I am not sure exactly how many channels there are, and how they map to the CPTS inputs. But hopefully with a bit of trial and error we can figure out if there is a channel associated with HWxTSPUSH.

Regards,

Nick