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Message-ID: <20241031085245.18146-4-darinzon@amazon.com>
Date: Thu, 31 Oct 2024 10:52:44 +0200
From: David Arinzon <darinzon@...zon.com>
To: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
<netdev@...r.kernel.org>
CC: David Arinzon <darinzon@...zon.com>, Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>,
"Woodhouse, David" <dwmw@...zon.com>, "Machulsky, Zorik" <zorik@...zon.com>,
"Matushevsky, Alexander" <matua@...zon.com>, Saeed Bshara
<saeedb@...zon.com>, "Wilson, Matt" <msw@...zon.com>, "Liguori, Anthony"
<aliguori@...zon.com>, "Bshara, Nafea" <nafea@...zon.com>, "Schmeilin,
Evgeny" <evgenys@...zon.com>, "Belgazal, Netanel" <netanel@...zon.com>,
"Saidi, Ali" <alisaidi@...zon.com>, "Herrenschmidt, Benjamin"
<benh@...zon.com>, "Kiyanovski, Arthur" <akiyano@...zon.com>, "Dagan, Noam"
<ndagan@...zon.com>, "Bernstein, Amit" <amitbern@...zon.com>, "Agroskin,
Shay" <shayagr@...zon.com>, "Abboud, Osama" <osamaabb@...zon.com>,
"Ostrovsky, Evgeny" <evostrov@...zon.com>, "Tabachnik, Ofir"
<ofirt@...zon.com>, "Machnikowski, Maciek" <maciek@...hnikowski.net>
Subject: [PATCH v2 net-next 3/3] net: ena: Add PHC documentation
Provide the relevant information and guidelines
about the feature support in the ENA driver.
Signed-off-by: Amit Bernstein <amitbern@...zon.com>
Signed-off-by: David Arinzon <darinzon@...zon.com>
---
.../device_drivers/ethernet/amazon/ena.rst | 78 +++++++++++++++++++
1 file changed, 78 insertions(+)
diff --git a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
index 4561e8ab..12665ea8 100644
--- a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
+++ b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
@@ -56,6 +56,7 @@ 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)
================= ======================================================
Management Interface:
@@ -221,6 +222,83 @@ 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 accuracy.
+
+**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.
+
+- ``CONFIG_PTP_1588_CLOCK=y``: the PTP module is already compiled and loaded inside the kernel binary file.
+
+- ``CONFIG_PTP_1588_CLOCK=m``: the PTP module needs to be loaded prior to loading the ENA driver:
+
+Load PTP module:
+
+.. code-block:: shell
+
+ sudo modprobe ptp
+
+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 statistic.
+
+**PHC statistics**
+
+PHC can be monitored using :code:`ethtool -S` counters:
+
+================= ======================================================
+**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** Number of failed get time attempts (entering into block state).
+================= ======================================================
+
+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
==========
--
2.40.1
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