xref: /openbmc/linux/Documentation/ABI/testing/debugfs-driver-dcc (revision 9a87ffc99ec8eb8d35eed7c4f816d75f5cc9662e)

What:           /sys/kernel/debug/dcc/.../ready
Date:           December 2022
Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Description:
		This file is used to check the status of the dcc
		hardware if it's ready to receive user configurations.
		A 'Y' here indicates dcc is ready.

What:           /sys/kernel/debug/dcc/.../trigger
Date:           December 2022
Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Description:
		This is the debugfs interface for manual software
		triggers. The trigger can be invoked by writing '1'
		to the file.

What:           /sys/kernel/debug/dcc/.../config_reset
Date:           December 2022
Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Description:
		This file is used to reset the configuration of
		a dcc driver to the default configuration. When '1'
		is written to the file, all the previous addresses
		stored in the driver gets removed and users need to
		reconfigure addresses again.

What:           /sys/kernel/debug/dcc/.../[list-number]/config
Date:		 December 2022
Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Description:
		This stores the addresses of the registers which
		can be read in case of a hardware crash or manual
		software triggers. The input addresses type
		can be one of following dcc instructions: read,
		write, read-write, and loop type. The lists need to
		be configured sequentially and not in a overlapping
		manner; e.g. users can jump to list x only after
		list y is configured and enabled. The input format for
		each type is as follows:

	        i) Read instruction

		   ::

		     echo R <addr> <n> <bus> >/sys/kernel/debug/dcc/../[list-number]/config

		   where:

		   <addr>
			The address to be read.

		   <n>
			The addresses word count, starting from address <1>.
			Each word is 32 bits (4 bytes). If omitted, defaulted
			to 1.

		   <bus type>
			The bus type, which can be either 'apb' or 'ahb'.
			The default is 'ahb' if leaved out.

		ii) Write instruction

		    ::

		      echo W <addr> <n> <bus type> > /sys/kernel/debug/dcc/../[list-number]/config

		    where:

		    <addr>
			The address to be written.

		    <n>
			The value to be written at <addr>.

		    <bus type>
			The bus type, which can be either 'apb' or 'ahb'.

	        iii) Read-write instruction

		     ::

		       echo RW <addr> <n> <mask> > /sys/kernel/debug/dcc/../[list-number]/config

		     where:

		     <addr>
			The address to be read and written.

		     <n>
		        The value to be written at <addr>.

		     <mask>
			The value mask.

		iv) Loop instruction

		    ::

		      echo L <loop count> <address count> <address>... > /sys/kernel/debug/dcc/../[list-number]/config

		    where:

		    <loop count>
			Number of iterations

		    <address count>
			total number of addresses to be written

		    <address>
			Space-separated list of addresses.

What:           /sys/kernel/debug/dcc/.../[list-number]/enable
Date:           December 2022
Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Description:
		This debugfs interface is used for enabling the
		the dcc hardware. A file named "enable" is in the
		directory list number where users can enable/disable
		the specific list by writing boolean (1 or 0) to the
		file.

		On enabling the dcc, all the addresses specified
		by the user for the corresponding list is written
		into dcc sram which is read by the dcc hardware
		on manual or crash induced triggers. Lists must
		be configured and enabled sequentially, e.g. list
		2 can only be enabled when list 1 have so.