PROCESSOR-SDK-AM64X: AM64x PTP related question

Hello Matt, 

1. What Linux SDK version are you using?

2. Are both your grandmaster and follower device a TI AM64x EVM?

3. What are the contents of your gPTP.cfg file?

Matt Tsai52 said:

Does the rms offset between grandmaster and slave look reasonable? If not, how can we fix it?

From tests I've ran in the past the rms offset should typically be in the double-digit ns level. So, we need to figure out what are the differences between your test setup and mine.

-Daolin

Hi Daolin,

For #1, #2:

Yes, both the PTP grandmaster and slave are running on TI AM64x EVM, with the default SDK on SD card.

root@am64xx-evm:~/# uname -a
Linux am64xx-evm 6.6.58-ti-01497-ga7758da17c28-dirty #1 SMP PREEMPT Wed Nov 27 13:23:15 UTC 2024 aarch64 GNU/Linux

For #3: The gPTP.cfg was taken from https://github.com/richardcochran/linuxptp/blob/master/configs/gPTP.cfg (as suggested by some TI instruction):

root@am64xx-evm:~/# cat gPTP.cfg
#
# 802.1AS example configuration containing those attributes which
# differ from the defaults.  See the file, default.cfg, for the
# complete list of available options.
#
[global]
gmCapable               1
priority1               248
priority2               248
logAnnounceInterval     0
logSyncInterval         -3
syncReceiptTimeout      3
neighborPropDelayThresh 800
min_neighbor_prop_delay -20000000
assume_two_step         1
path_trace_enabled      1
follow_up_info          1
transportSpecific       0x1
ptp_dst_mac             01:80:C2:00:00:0E
network_transport       L2
delay_mechanism         P2P

# Add these lines for the TI PHY:
ingressLatency 88
egressLatency  288

Hi Matt, 

Matt Tsai52 said:

root@am64xx-evm:~/# uname -a
Linux am64xx-evm 6.6.58-ti-01497-ga7758da17c28-dirty #1 SMP PREEMPT Wed Nov 27 13:23:15 UTC 2024 aarch64 GNU/Linux

Any particular reason for using non-RT Linux vs RT Linux? (I noticed you're not using PREEMPT_RT)

Matt Tsai52 said:

priority1               248

Can you try configuring "priority1" in your gPTP.cfg to be "100" for the grandmaster and "240" for the follower?

-Daolin

Hi Daolin,

I used non-RT Linux because that is on the TI AM64x EVM SD card and the instructions I found online do not seem to mention to use RT Linux for TSN features.

Here is the output on the slave side after changing the gPTP.cfg as you suggested:

ptp4l[378.503]: selected /dev/ptp0 as PTP clock
ptp4l[378.554]: port 1 (eth0): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[378.554]: port 0 (/var/run/ptp4l): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[378.554]: port 0 (/var/run/ptp4lro): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[381.879]: port 1 (eth0): new foreign master 70ff76.fffe.1fe2de-1
ptp4l[381.907]: selected local clock 641c10.fffe.24678f as best master
ptp4l[383.879]: selected best master clock 70ff76.fffe.1fe2de
ptp4l[383.879]: port 1 (eth0): LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[384.846]: port 1 (eth0): UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[385.473]: rms 38884 max 77824 freq  +4611 +/- 2133 delay    33 +/-   0
ptp4l[386.473]: rms 1090 max 1413 freq  +7261 +/- 796 delay    33 +/-   0
ptp4l[387.474]: rms 1099 max 1424 freq  +8580 +/- 132 delay    33 +/-   0
ptp4l[388.474]: rms  512 max  641 freq  +8553 +/- 164 delay    33 +/-   0
ptp4l[389.475]: rms  291 max  445 freq  +7674 +/- 272 delay    33 +/-   0
ptp4l[390.475]: rms  239 max  371 freq  +7523 +/- 244 delay    33 +/-   0
ptp4l[391.476]: rms  263 max  384 freq  +7934 +/- 319 delay    33 +/-   0
ptp4l[392.476]: rms  357 max  463 freq  +8484 +/- 190 delay    33 +/-   0
ptp4l[393.477]: rms  256 max  416 freq  +8657 +/- 119 delay    33 +/-   0
ptp4l[394.478]: rms  230 max  474 freq  +8724 +/- 251 delay    33 +/-   0
ptp4l[395.478]: rms  481 max  619 freq  +9525 +/- 100 delay    33 +/-   0
ptp4l[396.479]: rms  116 max  228 freq  +9204 +/- 140 delay    33 +/-   0
ptp4l[397.479]: rms  145 max  263 freq  +9365 +/- 132 delay    33 +/-   0
ptp4l[398.480]: rms  205 max  332 freq  +9215 +/- 289 delay    33 +/-   0
ptp4l[399.481]: rms  173 max  295 freq  +9264 +/- 242 delay    33 +/-   0
ptp4l[400.481]: rms  223 max  277 freq  +9673 +/- 100 delay    33 +/-   0
ptp4l[401.482]: rms  372 max  479 freq +10142 +/- 239 delay    33 +/-   0
ptp4l[402.482]: rms  195 max  393 freq +10199 +/- 112 delay    34 +/-   0
ptp4l[403.483]: rms  377 max  488 freq  +9382 +/- 253 delay    34 +/-   0
ptp4l[404.483]: rms  348 max  454 freq  +9008 +/-  89 delay    34 +/-   0
ptp4l[405.484]: rms  327 max  386 freq  +8710 +/- 138 delay    34 +/-   0
ptp4l[406.484]: rms  245 max  384 freq  +9111 +/- 337 delay    34 +/-   0
ptp4l[407.485]: rms  155 max  282 freq  +9257 +/- 172 delay    34 +/-   0
ptp4l[408.485]: rms  402 max  541 freq  +9914 +/- 171 delay    34 +/-   0
ptp4l[409.486]: rms  437 max  611 freq  +8859 +/- 355 delay    33 +/-   0
ptp4l[410.486]: rms  339 max  488 freq  +8603 +/- 276 delay    33 +/-   0
ptp4l[411.487]: rms  231 max  384 freq  +9075 +/- 278 delay    34 +/-   0
ptp4l[412.487]: rms  125 max  168 freq  +9110 +/- 145 delay    33 +/-   0
ptp4l[413.488]: rms  538 max  702 freq  +8104 +/- 361 delay    33 +/-   

Any comments?

Thank you for your help!

HI Daolin,

Just checking the status of this, do you have any insights on why the rms offsets are not double digits and how to improve?

Thank you! 

Hi Matt, 

Apologies for the delay in response.

Matt Tsai52 said:

For #1, #2:

Yes, both the PTP grandmaster and slave are running on TI AM64x EVM, with the default SDK on SD card.

root@am64xx-evm:~/# uname -a
Linux am64xx-evm 6.6.58-ti-01497-ga7758da17c28-dirty #1 SMP PREEMPT Wed Nov 27 13:23:15 UTC 2024 aarch64 GNU/Linux

Are you able to replicate the same PTP offset on SDK 11.1 (which should be kernel version 6.12.x)? 

It might be worth checking if the RT-Linux version will also produce the same rms offsets, just as a sanity check or comparison with non-RT.

Just to clarify, you are using CPSW Ethernet (and not ICSSG Ethernet) to test PTP?

Here is what I found when testing on AM64x EVM1 eth0 <----> eth0 AM64x EVM2, where eth0 is CPSW Ethernet and using RT-Linux SDK 11.1. With this configuration, I see the expected 2-digit offset values.

EVM1- Grandmaster

root@am64xx-evm:~# cat gPTP.cfg 
# 802.1AS example configuration containing those attributes which
# differ from the defaults. See the file, default.cfg, for the
# complete list of available options.
#
[global]
gmCapable 1
priority1 100
priority2 248
logAnnounceInterval 0
logSyncInterval -3
syncReceiptTimeout 3
neighborPropDelayThresh 800
min_neighbor_prop_delay -20000000
assume_two_step 1
path_trace_enabled 1
follow_up_info 1
transportSpecific 0x1
ptp_dst_mac 01:80:C2:00:00:0E
network_transport L2
delay_mechanism P2P
ingressLatency 96
egressLatency 288
root@am64xx-evm:~# ptp4l -P -2 -H -i eth0 -f gPTP.cfg --step_threshold=1 -m -q -p /dev/ptp0     
ptp4l[1261.577]: selected /dev/ptp0 as PTP clock
ptp4l[1261.605]: port 1 (eth0): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1261.605]: port 0 (/var/run/ptp4l): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1261.606]: port 0 (/var/run/ptp4lro): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1265.107]: port 1 (eth0): new foreign master 1c6349.fffe.1ad7bc-1
ptp4l[1265.594]: port 1 (eth0): LISTENING to MASTER on ANNOUNCE_RECEIPT_TIMEOUT_EXPIRES
ptp4l[1265.595]: selected local clock 3408e1.fffe.80a7ad as best master
ptp4l[1265.595]: port 1 (eth0): assuming the grand master role
ptp4l[1267.108]: selected best master clock 1c6349.fffe.1ad7bc
ptp4l[1267.108]: port 1 (eth0): assuming the grand master role
^Croot@am64xx-evm:~# uname -a
Linux am64xx-evm 6.12.35-g563c0d3bd742 #6 SMP PREEMPT_RT Thu Aug 14 15:16:24 CDT 2025 aarch64 GNU/Lx
root@am64xx-evm:~#

EVM2- Follower

root@am64xx-evm:~# cat gPTP.cfg 
# 802.1AS example configuration containing those attributes which
# differ from the defaults. See the file, default.cfg, for the
# complete list of available options.
#
[global]
gmCapable 1
priority1 240
priority2 248
logAnnounceInterval 0
logSyncInterval -3
syncReceiptTimeout 3
neighborPropDelayThresh 800
min_neighbor_prop_delay -20000000
assume_two_step 1
path_trace_enabled 1
follow_up_info 1
transportSpecific 0x1
ptp_dst_mac 01:80:C2:00:00:0E
network_transport L2
delay_mechanism P2P
ingressLatency 96
egressLatency 288

root@am64xx-evm:~# ptp4l -P -2 -H -i eth0 -f gPTP.cfg --step_threshold=1 -m -q -p /dev/ptp0     
ptp4l[1257.220]: selected /dev/ptp0 as PTP clock
ptp4l[1257.251]: port 1 (eth0): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1257.252]: port 0 (/var/run/ptp4l): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1257.252]: port 0 (/var/run/ptp4lro): INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[1261.220]: port 1 (eth0): LISTENING to MASTER on ANNOUNCE_RECEIPT_TIMEOUT_EXPIRES
ptp4l[1261.221]: selected local clock 1c6349.fffe.1ad7bc as best master
ptp4l[1261.221]: port 1 (eth0): assuming the grand master role
ptp4l[1262.710]: port 1 (eth0): new foreign master 3408e1.fffe.80a7ad-1
ptp4l[1263.335]: port 1 (eth0): received SYNC without timestamp
ptp4l[1264.210]: port 1 (eth0): received SYNC without timestamp
ptp4l[1264.711]: selected best master clock 3408e1.fffe.80a7ad
ptp4l[1264.711]: port 1 (eth0): MASTER to UNCALIBRATED on RS_SLAVE
ptp4l[1265.461]: port 1 (eth0): UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[1266.212]: rms 15114 max 19954 freq +16779 +/- 10396 delay  27 +/-  0
ptp4l[1267.212]: rms 2787 max 4269 freq +7682 +/- 3785 delay  27 +/-  0
ptp4l[1267.462]: port 1 (eth0): received SYNC without timestamp
ptp4l[1268.338]: rms 4737 max 5028 freq  -948 +/- 1247 delay  27 +/-  0
ptp4l[1269.339]: rms 2929 max 3924 freq -2476 +/- 139 delay  27 +/-  0
ptp4l[1270.339]: rms 913 max 1527 freq -1504 +/- 352 delay  27 +/-  0
ptp4l[1271.340]: rms 181 max 281 freq  -487 +/- 215 delay  27 +/-  0
ptp4l[1272.340]: rms 282 max 303 freq  -19 +/- 66 delay  26 +/-  0
ptp4l[1273.341]: rms 170 max 231 freq  +60 +/-  9 delay  26 +/-  0
ptp4l[1274.342]: rms  53 max  90 freq   +2 +/- 24 delay  27 +/-  0
ptp4l[1274.721]: port 1 (eth0): received PDELAY_REQ without timestamp
ptp4l[1275.342]: rms  38 max  56 freq  -104 +/- 32 delay  27 +/-  0
ptp4l[1276.343]: rms  21 max  37 freq  -116 +/- 10 delay  27 +/-  0
ptp4l[1277.343]: rms  8 max  13 freq  -88 +/-  8 delay  27 +/-  0
ptp4l[1278.344]: rms  11 max  14 freq  -72 +/-  5 delay  27 +/-  0
ptp4l[1279.345]: rms  4 max  7 freq  -76 +/-  4 delay  27 +/-  0
ptp4l[1280.345]: rms  5 max  9 freq  -85 +/-  5 delay  27 +/-  0
^Croot@am64xx-evm:~# uname -a
Linux am64xx-evm 6.12.35-g563c0d3bd742 #6 SMP PREEMPT_RT Thu Aug 14 15:16:24 CDT 2025 aarch64 GNU/Lx
root@am64xx-evm:~# 

-Daolin

Hi Daolin,

Thank you for the response. 
I believe I tested PTP with CPSW Ethernet. I roughly followed this TI webinar presentation to set up EVM1 as a switch (without cut-through), then testing PTP with EVM1 eth1 <--> EVM2 eth0
e2e.ti.com/.../TI-Sitara-Linux-TSN-webinar.pdf
Please explain if you think I might be using the ICSSG Ethernet.

I am willing to try SDK 11.1 with both non-RT kernel and RT kernel.
Can you please point out how do I obtain both images for the SD card?

Thank you for your help!

Hi Matt, 

Apologies again for the delay in response as I was/am out of office this week.

Matt Tsai52 said:

I am willing to try SDK 11.1 with both non-RT kernel and RT kernel.
Can you please point out how do I obtain both images for the SD card?

You can find the SDK 11.1 RT wic image here: https://www.ti.com/tool/de-de/download/PROCESSOR-SDK-LINUX-RT-AM64X 

For SDK 11.1 non-RT wic image: https://www.ti.com/tool/de-de/download/PROCESSOR-SDK-LINUX-AM64X 

Matt Tsai52 said:

I believe I tested PTP with CPSW Ethernet. I roughly followed this TI webinar presentation to set up EVM1 as a switch (without cut-through), then testing PTP with EVM1 eth1 <--> EVM2 eth0
e2e.ti.com/.../TI-Sitara-Linux-TSN-webinar.pdf
Please explain if you think I might be using the ICSSG Ethernet.

The webinar assumes that you are using the TI provided wic image. Based on that and assuming you made no changes to device tree or device tree overlay, both eth0 and eth1 by default are using CPSW Ethernet. 

-Daolin

Thank you, Daolin!

I will try PTP on SDK 11.1 and let you know the results. It may take a while. Thank you.