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+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Texas Instruments TPS6594 PFSM driver
+=====================================
+
+Author: Julien Panis (jpanis@baylibre.com)
+
+Overview
+========
+
+Strictly speaking, PFSM (Pre-configurable Finite State Machine) is not
+hardware. It is a piece of code.
+
+The TPS6594 PMIC (Power Management IC) integrates a state machine which
+manages operational modes. Depending on the current operational mode,
+some voltage domains remain energized while others can be off.
+
+The PFSM driver can be used to trigger transitions between configured
+states. It also provides R/W access to the device registers.
+
+Supported chips
+---------------
+
+- tps6594-q1
+- tps6593-q1
+- lp8764-q1
+
+Driver location
+===============
+
+drivers/misc/tps6594-pfsm.c
+
+Driver type definitions
+=======================
+
+include/uapi/linux/tps6594_pfsm.h
+
+Driver IOCTLs
+=============
+
+:c:macro::`PMIC_GOTO_STANDBY`
+All device resources are powered down. The processor is off, and
+no voltage domains are energized.
+
+:c:macro::`PMIC_GOTO_LP_STANDBY`
+The digital and analog functions of the PMIC, which are not
+required to be always-on, are turned off (low-power).
+
+:c:macro::`PMIC_UPDATE_PGM`
+Triggers a firmware update.
+
+:c:macro::`PMIC_SET_ACTIVE_STATE`
+One of the operational modes.
+The PMICs are fully functional and supply power to all PDN loads.
+All voltage domains are energized in both MCU and Main processor
+sections.
+
+:c:macro::`PMIC_SET_MCU_ONLY_STATE`
+One of the operational modes.
+Only the power resources assigned to the MCU Safety Island are on.
+
+:c:macro::`PMIC_SET_RETENTION_STATE`
+One of the operational modes.
+Depending on the triggers set, some DDR/GPIO voltage domains can
+remain energized, while all other domains are off to minimize
+total system power.
+
+Driver usage
+============
+
+See available PFSMs::
+
+ # ls /dev/pfsm*
+
+Dump the registers of pages 0 and 1::
+
+ # hexdump -C /dev/pfsm-0-0x48
+
+See PFSM events::
+
+ # cat /proc/interrupts
+
+Userspace code example
+----------------------
+
+samples/pfsm/pfsm-wakeup.c