Merge branch 'phc-support-in-ena-driver'

David Arinzon says:

====================
PHC support in ENA driver

This patchset adds the support for PHC (PTP Hardware Clock)
in the ENA driver. The documentation part of the patchset
includes additional information, including statistics,
utilization and invocation examples through the testptp
utility.
====================

Link: https://patch.msgid.link/20250617110545.5659-1-darinzon@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 111 insertions, 0 deletions

diff --git a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
index 4561e8ab9e08..14784a0a6a8a 100644
--- a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
+++ b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
@@ -56,6 +56,9 @@ ena_netdev.[ch]     Main Linux kernel driver.
 ena_ethtool.c       ethtool callbacks.
 ena_xdp.[ch]        XDP files
 ena_pci_id_tbl.h    Supported device IDs.
+ena_phc.[ch]        PTP hardware clock infrastructure (see `PHC`_ for more info)
+ena_devlink.[ch]    devlink files.
+ena_debugfs.[ch]    debugfs files.
 =================   ======================================================
 
 Management Interface:
@@ -221,6 +224,99 @@ descriptor it was received on would be recycled. When a packet smaller
 than RX copybreak bytes is received, it is copied into a new memory
 buffer and the RX descriptor is returned to HW.
 
+.. _`PHC`:
+
+PTP Hardware Clock (PHC)
+========================
+.. _`ptp-userspace-api`: https://docs.kernel.org/driver-api/ptp.html#ptp-hardware-clock-user-space-api
+.. _`testptp`: https://elixir.bootlin.com/linux/latest/source/tools/testing/selftests/ptp/testptp.c
+
+ENA Linux driver supports PTP hardware clock providing timestamp reference to achieve nanosecond resolution.
+
+**PHC support**
+
+PHC depends on the PTP module, which needs to be either loaded as a module or compiled into the kernel.
+
+Verify if the PTP module is present:
+
+.. code-block:: shell
+
+  grep -w '^CONFIG_PTP_1588_CLOCK=[ym]' /boot/config-`uname -r`
+
+- If no output is provided, the ENA driver cannot be loaded with PHC support.
+
+**PHC activation**
+
+The feature is turned off by default, in order to turn the feature on, the ENA driver
+can be loaded in the following way:
+
+- devlink:
+
+.. code-block:: shell
+
+  sudo devlink dev param set pci/<domain:bus:slot.function> name enable_phc value true cmode driverinit
+  sudo devlink dev reload pci/<domain:bus:slot.function>
+  # for example:
+  sudo devlink dev param set pci/0000:00:06.0 name enable_phc value true cmode driverinit
+  sudo devlink dev reload pci/0000:00:06.0
+
+All available PTP clock sources can be tracked here:
+
+.. code-block:: shell
+
+  ls /sys/class/ptp
+
+PHC support and capabilities can be verified using ethtool:
+
+.. code-block:: shell
+
+  ethtool -T <interface>
+
+**PHC timestamp**
+
+To retrieve PHC timestamp, use `ptp-userspace-api`_, usage example using `testptp`_:
+
+.. code-block:: shell
+
+  testptp -d /dev/ptp$(ethtool -T <interface> | awk '/PTP Hardware Clock:/ {print $NF}') -k 1
+
+PHC get time requests should be within reasonable bounds,
+avoid excessive utilization to ensure optimal performance and efficiency.
+The ENA device restricts the frequency of PHC get time requests to a maximum
+of 125 requests per second. If this limit is surpassed, the get time request
+will fail, leading to an increment in the phc_err_ts statistic.
+
+**PHC statistics**
+
+PHC can be monitored using debugfs (if mounted):
+
+.. code-block:: shell
+
+  sudo cat /sys/kernel/debug/<domain:bus:slot.function>/phc_stats
+
+  # for example:
+  sudo cat /sys/kernel/debug/0000:00:06.0/phc_stats
+
+PHC errors must remain below 1% of all PHC requests to maintain the desired level of accuracy and reliability
+
+=================   ======================================================
+**phc_cnt**         | Number of successful retrieved timestamps (below expire timeout).
+**phc_exp**         | Number of expired retrieved timestamps (above expire timeout).
+**phc_skp**         | Number of skipped get time attempts (during block period).
+**phc_err_dv**      | Number of failed get time attempts due to device errors (entering into block state).
+**phc_err_ts**      | Number of failed get time attempts due to timestamp errors (entering into block state),
+                    | This occurs if driver exceeded the request limit or device received an invalid timestamp.
+=================   ======================================================
+
+PHC timeouts:
+
+=================   ======================================================
+**expire**          | Max time for a valid timestamp retrieval, passing this threshold will fail
+                    | the get time request and block new requests until block timeout.
+**block**           | Blocking period starts once get time request expires or fails,
+                    | all get time requests during block period will be skipped.
+=================   ======================================================
+
 Statistics
 ==========
 
@@ -268,6 +364,18 @@ RSS
 - The user can provide a hash key, hash function, and configure the
   indirection table through `ethtool(8)`.
 
+DEVLINK SUPPORT
+===============
+.. _`devlink`: https://www.kernel.org/doc/html/latest/networking/devlink/index.html
+
+`devlink`_ supports reloading the driver and initiating re-negotiation with the ENA device
+
+.. code-block:: shell
+
+  sudo devlink dev reload pci/<domain:bus:slot.function>
+  # for example:
+  sudo devlink dev reload pci/0000:00:06.0
+
 DATA PATH
 =========
 
diff --git a/Documentation/networking/devlink/devlink-params.rst b/Documentation/networking/devlink/devlink-params.rst
index 4e01dc32bc08..3da8f4ef2417 100644
--- a/Documentation/networking/devlink/devlink-params.rst
+++ b/Documentation/networking/devlink/devlink-params.rst
@@ -137,3 +137,6 @@ own name.
    * - ``event_eq_size``
      - u32
      - Control the size of asynchronous control events EQ.
+   * - ``enable_phc``
+     - Boolean
+     - Enable PHC (PTP Hardware Clock) functionality in the device.