xref: /openbmc/linux/Documentation/ABI/testing/sysfs-devices-soc (revision 4f2c0a4acffbec01079c28f839422e64ddeff004)

What:		/sys/devices/socX
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		The /sys/devices/ directory contains a sub-directory for each
		System-on-Chip (SoC) device on a running platform. Information
		regarding each SoC can be obtained by reading sysfs files. This
		functionality is only available if implemented by the platform.

		The directory created for each SoC will also house information
		about devices which are commonly contained in /sys/devices/platform.
		It has been agreed that if an SoC device exists, its supported
		devices would be better suited to appear as children of that SoC.

What:		/sys/devices/socX/machine
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		Read-only attribute common to all SoCs. Contains the SoC machine
		name (e.g. Ux500).

What:		/sys/devices/socX/family
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		Read-only attribute common to all SoCs. Contains SoC family name
		(e.g. DB8500).

		On many of ARM based silicon with SMCCC v1.2+ compliant firmware
		this will contain the JEDEC JEP106 manufacturer’s identification
		code. The format is "jep106:XXYY" where XX is identity code and
		YY is continuation code.

		This manufacturer’s identification code is defined by one
		or more eight (8) bit fields, each consisting of seven (7)
		data bits plus one (1) odd parity bit. It is a single field,
		limiting the possible number of vendors to 126. To expand
		the maximum number of identification codes, a continuation
		scheme has been defined.

		The specified mechanism is that an identity code of 0x7F
		represents the "continuation code" and implies the presence
		of an additional identity code field, and this mechanism
		may be extended to multiple continuation codes followed
		by the manufacturer's identity code.

		For example, ARM has identity code 0x7F 0x7F 0x7F 0x7F 0x3B,
		which is code 0x3B on the fifth 'page'. This is shortened
		as JEP106 identity code of 0x3B and a continuation code of
		0x4 to represent the four continuation codes preceding the
		identity code.

What:		/sys/devices/socX/serial_number
Date:		January 2019
contact:	Bjorn Andersson <bjorn.andersson@linaro.org>
Description:
		Read-only attribute supported by most SoCs. Contains the SoC's
		serial number, if available.

What:		/sys/devices/socX/soc_id
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		Read-only attribute supported by most SoCs. In the case of
		ST-Ericsson's chips this contains the SoC serial number.

		On many of ARM based silicon with SMCCC v1.2+ compliant firmware
		this will contain the SOC ID appended to the family attribute
		to ensure there is no conflict in this namespace across various
		vendors. The format is "jep106:XXYY:ZZZZ" where XX is identity
		code, YY is continuation code and ZZZZ is the SOC ID.

What:		/sys/devices/socX/revision
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		Read-only attribute supported by most SoCs. Contains the SoC's
		manufacturing revision number.

What:		/sys/devices/socX/process
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		Read-only attribute supported ST-Ericsson's silicon. Contains the
		the process by which the silicon chip was manufactured.

What:		/sys/bus/soc
Date:		January 2012
contact:	Lee Jones <lee@kernel.org>
Description:
		The /sys/bus/soc/ directory contains the usual sub-folders
		expected under most buses. /sys/bus/soc/devices is of particular
		interest, as it contains a symlink for each SoC device found on
		the system. Each symlink points back into the aforementioned
		/sys/devices/socX devices.