docs: ABI: testing: Document the OCC hwmon FFDC binary interface

Add documentation for the new binary sysfs that will dump the SBEFIFO
FFDC.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20211019205307.36946-4-eajames@linux.ibm.com
Signed-off-by: Joel Stanley <joel@jms.id.au>

diff --git a/Documentation/ABI/testing/sysfs-bus-platform-devices-occ-hwmon b/Documentation/ABI/testing/sysfs-bus-platform-devices-occ-hwmon
new file mode 100644 (file)
index 0000000..b24d7ab
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-platform-devices-occ-hwmon
@@ -0,0 +1,13 @@
+What:          /sys/bus/platform/devices/occ-hwmon.X/ffdc
+KernelVersion: 5.15
+Contact:       eajames@linux.ibm.com
+Description:
+               Contains the First Failure Data Capture from the SBEFIFO
+               hardware, if there is any from a previous transfer. Otherwise,
+               the file is empty. The data is cleared when it's been
+               completely read by a user. As the name suggests, only the data
+               from the first error is saved, until it's cleared upon read. The OCC hwmon driver, running on
+               a Baseboard Management Controller (BMC), communicates with
+               POWER9 and up processors over the Self-Boot Engine (SBE) FIFO.
+               In many error conditions, the SBEFIFO will return error data
+               indicating the type of error and system state, etc.