firmware: rsu: document sysfs interface

Describe Intel Stratix10 Remote System Update (RSU) device attributes
Signed-off-by: Richard Gong <richard.gong@intel.com>
Reviewed-by: Alan Tull <atull@kernel.org>
Link: https://lore.kernel.org/r/1567516701-26026-4-git-send-email-richard.gong@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-devices-platform-stratix10-rsu

+	Intel Stratix10 Remote System Update (RSU) device attributes
+
+What:		/sys/devices/platform/stratix10-rsu.0/current_image
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the address in flash of currently running image.
+
+What:		/sys/devices/platform/stratix10-rsu.0/fail_image
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the address in flash of failed image.
+
+What:		/sys/devices/platform/stratix10-rsu.0/state
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the state of RSU system.
+		The state field has two parts: major error code in
+		upper 16 bits and minor error code in lower 16 bits.
+
+		b[15:0]
+			Currently used only when major error is 0xF006
+			(CPU watchdog timeout), in which case the minor
+			error code is the value reported by CPU to
+			firmware through the RSU notify command before
+			the watchdog timeout occurs.
+
+		b[31:16]
+			0xF001	bitstream error
+			0xF002	hardware access failure
+			0xF003	bitstream corruption
+			0xF004	internal error
+			0xF005	device error
+			0xF006	CPU watchdog timeout
+			0xF007	internal unknown error
+
+What:		/sys/devices/platform/stratix10-rsu.0/version
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the version number of RSU firmware. 19.3 or late
+		version includes information about the firmware which
+		reported the error.
+
+		pre 19.3:
+			b[31:0]
+				0x0	version number
+
+		19.3 or late:
+			b[15:0]
+				0x1	version number
+			b[31:16]
+				0x0	no error
+				0x0DCF	Decision CMF error
+				0x0ACF	Application CMF error
+
+What:		/sys/devices/platform/stratix10-rsu.0/error_location
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the error offset inside the image that failed.
+
+What:		/sys/devices/platform/stratix10-rsu.0/error_details
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) error code.
+
+What:		/sys/devices/platform/stratix10-rsu.0/retry_counter
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(RO) the current image's retry counter, which is used by
+		user to know how many times the images is still allowed
+		to reload itself before giving up and starting RSU
+		fail-over flow.
+
+What:		/sys/devices/platform/stratix10-rsu.0/reboot_image
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(WO) the address in flash of image to be loaded on next
+		reboot command.
+
+What:		/sys/devices/platform/stratix10-rsu.0/notify
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Richard Gong <richard.gong@linux.intel.com>
+Description:
+		(WO) client to notify firmware with different actions.
+
+		b[15:0]
+			inform firmware the current software execution
+			stage.
+			0	the first stage bootloader didn't run or
+				didn't reach the point of launching second
+				stage bootloader.
+			1	failed in second bootloader or didn't get
+				to the point of launching the operating
+				system.
+			2	both first and second stage bootloader ran
+				and the operating system launch was
+				attempted.
+
+		b[16]
+			1	firmware to reset current image retry
+				counter.
+			0	no action.
+
+		b[17]
+			1	firmware to clear RSU log
+			0	no action.
+
+		b[18]
+			this is negative logic
+			1	no action
+			0	firmware record the notify code defined
+				in b[15:0].