Documentation/ABI: Add document for Mellanox PMC driver

Document the sysfs interface for programming and monitoring the
performance counters in various HW blocks of Mellanox BlueField-1,
BlueField-2 and BlueField-3.

Signed-off-by: Shravan Kumar Ramani <shravankr@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/9a9e69bd99cad3ad8d1847a6e4e10aff80c6df50.1736413033.git.shravankr@nvidia.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/Documentation/ABI/testing/sysfs-platform-mellanox-pmc b/Documentation/ABI/testing/sysfs-platform-mellanox-pmc
new file mode 100644 (file)
index 0000000..9f987c6
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+HID           Driver         Description
+MLNXBFD0      mlxbf-pmc      Performance counters (BlueField-1)
+MLNXBFD1      mlxbf-pmc      Performance counters (BlueField-2)
+MLNXBFD2      mlxbf-pmc      Performance counters (BlueField-3)
+
+What:          /sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/event_list
+Date:          Dec 2020
+KernelVersion: 5.10
+Contact:       "Shravan Kumar Ramani <shravankr@nvidia.com>"
+Description:
+               List of events supported by the counters in the specific block.
+               It is used to extract the event number or ID associated with
+               each event.
+
+What:          /sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/event<N>
+Date:          Dec 2020
+KernelVersion: 5.10
+Contact:       "Shravan Kumar Ramani <shravankr@nvidia.com>"
+Description:
+               Event monitored by corresponding counter. This is used to
+               program or read back the event that should be or is currently
+               being monitored by counter<N>.
+
+What:          /sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/counter<N>
+Date:          Dec 2020
+KernelVersion: 5.10
+Contact:       "Shravan Kumar Ramani <shravankr@nvidia.com>"
+Description:
+               Counter value of the event being monitored. This is used to
+               read the counter value of the event which was programmed using
+               event<N>. This is also used to clear or reset the counter value
+               by writing 0 to the counter sysfs.
+
+What:          /sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/enable
+Date:          Dec 2020
+KernelVersion: 5.10
+Contact:       "Shravan Kumar Ramani <shravankr@nvidia.com>"
+Description:
+               Start or stop counters. This is used to start the counters
+               for monitoring the programmed events and also to stop the
+               counters after the desired duration. Writing value 1 will
+               start all the counters in the block, and writing 0 will
+               stop all the counters together.
+
+What:          /sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/<reg>
+Date:          Dec 2020
+KernelVersion: 5.10
+Contact:       "Shravan Kumar Ramani <shravankr@nvidia.com>"
+Description:
+               Value of register. This is used to read or reset the registers
+               where various performance statistics are counted for each block.
+               Writing 0 to the sysfs will clear the counter, writing any other
+               value is not allowed.
+