Merge branch 'mlx5-ptm-cross-timestamping-support'

Tariq Toukan says:

====================
mlx5 PTM cross timestamping support

This patchset by Rahul and Carolina adds PTM (Precision Time Measurement)
support to the mlx5 driver.

PTM is a PCI extended capability introduced by PCI-SIG for providing an
accurate read of the device clock offset without being impacted by
asymmetric bus transfer rates.

The performance of PTM on ConnectX-7 was evaluated using both real-time
(RTC) and free-running (FRC) clocks under traffic and no traffic
conditions. Tests with phc2sys measured the maximum offset values at a 50Hz
rate, with and without PTM.

Results:

1. No traffic
+-----+--------+--------+
|     | No-PTM | PTM    |
+-----+--------+--------+
| FRC | 125 ns | <29 ns |
+-----+--------+--------+
| RTC | 248 ns | <34 ns |
+-----+--------+--------+

2. With traffic
+-----+--------+--------+
|     | No-PTM | PTM    |
+-----+--------+--------+
| FRC | 254 ns | <40 ns |
+-----+--------+--------+
| RTC | 255 ns | <45 ns |
+-----+--------+--------+

v2: https://lore.kernel.org/d1dba3e1-2ecc-4fdf-a23b-7696c4bccf45@gmail.com
====================

Link: https://patch.msgid.link/20240730134055.1835261-1-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>