xref: /linux/Documentation/ABI/testing/debugfs-driver-dcc (revision dc2f5a499de420001813562ddbc9d51ece295978)

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 take the inputs. A 'Y'
		here indicates dcc is in a ready condition.
		Example:
		cat /sys/kernel/debug/dcc/.../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 user can simply enter a 1 against
		the debugfs file and enable a manual trigger.
		Example:
		echo  1 > /sys/kernel/debug/dcc/.../trigger

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. This
		means that all the previous addresses stored in
		the driver gets removed and user needs to enter
		the address values from the start.
		Example:
		echo  1 > /sys/kernel/debug/dcc/../config_reset

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
		should be read in case of a hardware crash or
		manual software triggers. The addresses entered here
		are considered under all the 4 types of dcc
		instructions Read type, Write type, Read Modify Write
		type and Loop type. The lists need to be configured
		sequentially and not in a overlapping manner. As an
		example user can jump to list x only after list y is
		configured and enabled. The format for entering all
		types of instructions are explained in examples as
		follows:

	        i) Read Type Instruction

		   echo R <1> <2> <3> >/sys/kernel/debug/dcc/../[list-number]/config

		   1->Address to be considered for reading the value.

		   2->The word count of the addresses, read n words
		      starting from address <1>. Each word is of 32 bits.
		      If not entered 1 is considered.

		   3->Can be 'apb' or 'ahb' which indicates if it is apb or ahb
		      bus respectively. If not entered ahb is considered.

		ii) Write Type Instruction

		    echo W <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		    1->Address to be considered for writing the value.

		    2->The value that needs to be written at the location.

		    3->Can be a 'apb' or 'ahb' which indicates if it is apb or ahb
		       but respectively.

	        iii) Read Modify Write type instruction

		     echo RW <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		     1->The address which needs to be considered for read then write.

		     2->The value that needs to be written on the address.

		     3->The mask of the value to be written.

		iv) Loop Type Instruction

		    echo L <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		    1->The loop count, the number of times the value of the addresses will be
		       captured.

		    2->The address count, total number of addresses to be entered in this
		       instruction.

		    3->The series of addresses to be entered separated by a space like <addr1>
		       <addr2>... and so on.

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. Enable file is kept under the
		directory list number for which the user wants
		to enable it. For example if the user wants to
		enable list 1, then he should go for
		echo 1 > /sys/kernel/debug/dcc/.../1/enable.
		On enabling the dcc, all the addresses entered
		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 should
		be enabled sequentially.For example after configuring
		addresses for list 1 and enabling it, a user can
		proceed to enable list 2 or vice versa.
		Example:
		echo  0 > /sys/kernel/debug/dcc/.../[list-number]/enable
		(disable dcc for the corresponding list number)
		echo  1 > /sys/kernel/debug/dcc/.../[list-number]/enable
		(enable dcc for the corresponding list number)