openwrt/target/linux/bcm27xx/patches-5.4/950-0986-gpio-Add-gpio-fsm-driver.patch

From c31626a9e173f2b2e0adc4cb8bfbb86a958bafcd Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 30 Sep 2020 12:00:54 +0100
Subject: [PATCH] gpio: Add gpio-fsm driver

The gpio-fsm driver implements simple state machines that allow GPIOs
to be controlled in response to inputs from other GPIOs - real and
soft/virtual - and time delays. It can:
+ create dummy GPIOs for drivers that demand them,
+ drive multiple GPIOs from a single input, with optional delays,
+ add a debounce circuit to an input,
+ drive pattern sequences onto LEDs
etc.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/gpio/Kconfig                |    9 +
 drivers/gpio/Makefile               |    1 +
 drivers/gpio/gpio-fsm.c             | 1103 +++++++++++++++++++++++++++
 include/dt-bindings/gpio/gpio-fsm.h |   21 +
 4 files changed, 1134 insertions(+)
 create mode 100644 drivers/gpio/gpio-fsm.c
 create mode 100644 include/dt-bindings/gpio/gpio-fsm.h

--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1071,6 +1071,15 @@ config HTC_EGPIO
 	  several HTC phones.  It provides basic support for input
 	  pins, output pins, and irqs.
 
+config GPIO_FSM
+	tristate "GPIO FSM support"
+	help
+	  The GPIO FSM driver allows the creation of state machines for
+	  manipulating GPIOs (both real and virtual), with state transitions
+	  triggered by GPIO edges or delays.
+
+	  If unsure, say N.
+
 config GPIO_JANZ_TTL
 	tristate "Janz VMOD-TTL Digital IO Module"
 	depends on MFD_JANZ_CMODIO
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_GPIO_EP93XX)		+= gpio-ep93x
 obj-$(CONFIG_GPIO_EXAR)			+= gpio-exar.o
 obj-$(CONFIG_GPIO_F7188X)		+= gpio-f7188x.o
 obj-$(CONFIG_GPIO_FTGPIO010)		+= gpio-ftgpio010.o
+obj-$(CONFIG_GPIO_FSM)			+= gpio-fsm.o
 obj-$(CONFIG_GPIO_GE_FPGA)		+= gpio-ge.o
 obj-$(CONFIG_GPIO_GPIO_MM)		+= gpio-gpio-mm.o
 obj-$(CONFIG_GPIO_GRGPIO)		+= gpio-grgpio.o
--- /dev/null
+++ b/drivers/gpio/gpio-fsm.c
@@ -0,0 +1,1103 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  GPIO FSM driver
+ *
+ *  This driver implements simple state machines that allow real GPIOs to be
+ *  controlled in response to inputs from other GPIOs - real and soft/virtual -
+ *  and time delays. It can:
+ *  + create dummy GPIOs for drivers that demand them
+ *  + drive multiple GPIOs from a single input,  with optional delays
+ *  + add a debounce circuit to an input
+ *  + drive pattern sequences onto LEDs
+ *  etc.
+ *
+ *  Copyright (C) 2020 Raspberry Pi (Trading) Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <dt-bindings/gpio/gpio-fsm.h>
+
+#define MODULE_NAME "gpio-fsm"
+
+#define GF_IO_TYPE(x) ((u32)(x) & 0xffff)
+#define GF_IO_INDEX(x) ((u32)(x) >> 16)
+
+enum {
+	SIGNAL_GPIO,
+	SIGNAL_SOFT
+};
+
+enum {
+	INPUT_GPIO,
+	INPUT_SOFT
+};
+
+enum {
+	SYM_UNDEFINED,
+	SYM_NAME,
+	SYM_SET,
+	SYM_START,
+	SYM_SHUTDOWN,
+
+	SYM_MAX
+};
+
+struct soft_gpio {
+	int dir;
+	int value;
+};
+
+struct input_gpio_state {
+	struct gpio_fsm *gf;
+	struct gpio_desc  *desc;
+	struct fsm_state *target;
+	int index;
+	int value;
+	int irq;
+	bool enabled;
+	bool active_low;
+};
+
+struct gpio_event {
+	int index;
+	int value;
+	struct fsm_state *target;
+};
+
+struct symtab_entry {
+	const char *name;
+	void *value;
+	struct symtab_entry *next;
+};
+
+struct output_signal {
+	u8 type;
+	u8 value;
+	u16 index;
+};
+
+struct fsm_state {
+	const char *name;
+	struct output_signal *signals;
+	struct gpio_event *gpio_events;
+	struct gpio_event *soft_events;
+	struct fsm_state *delay_target;
+	struct fsm_state *shutdown_target;
+	unsigned int num_signals;
+	unsigned int num_gpio_events;
+	unsigned int num_soft_events;
+	unsigned int delay_ms;
+	unsigned int shutdown_ms;
+};
+
+struct gpio_fsm {
+	struct gpio_chip gc;
+	struct device *dev;
+	spinlock_t spinlock;
+	struct work_struct work;
+	struct timer_list timer;
+	wait_queue_head_t shutdown_event;
+	struct fsm_state *states;
+	struct input_gpio_state *input_gpio_states;
+	struct gpio_descs *input_gpios;
+	struct gpio_descs *output_gpios;
+	struct soft_gpio *soft_gpios;
+	struct fsm_state *start_state;
+	struct fsm_state *shutdown_state;
+	unsigned int num_states;
+	unsigned int num_output_gpios;
+	unsigned int num_input_gpios;
+	unsigned int num_soft_gpios;
+	unsigned int shutdown_timeout_ms;
+	unsigned int shutdown_jiffies;
+
+	struct fsm_state *current_state;
+	struct fsm_state *next_state;
+	struct fsm_state *delay_target_state;
+	int delay_ms;
+	unsigned int debug;
+	bool shutting_down;
+	struct symtab_entry *symtab;
+};
+
+static struct symtab_entry *do_add_symbol(struct symtab_entry **symtab,
+					  const char *name, void *value)
+{
+	struct symtab_entry **p = symtab;
+
+	while (*p && strcmp((*p)->name, name))
+		p = &(*p)->next;
+
+	if (*p) {
+		/* This is an existing symbol */
+		if ((*p)->value) {
+			/* Already defined */
+			if (value) {
+				if ((uintptr_t)value < SYM_MAX)
+					return ERR_PTR(-EINVAL);
+				else
+					return ERR_PTR(-EEXIST);
+			}
+		} else {
+			/* Undefined */
+			(*p)->value = value;
+		}
+	} else {
+		/* This is a new symbol */
+		*p = kmalloc(sizeof(struct symtab_entry), GFP_KERNEL);
+		if (*p) {
+			(*p)->name = name;
+			(*p)->value = value;
+			(*p)->next = NULL;
+		}
+	}
+	return *p;
+}
+
+static int add_symbol(struct symtab_entry **symtab,
+		      const char *name, void *value)
+{
+	struct symtab_entry *sym = do_add_symbol(symtab, name, value);
+
+	return PTR_ERR_OR_ZERO(sym);
+}
+
+static struct symtab_entry *get_symbol(struct symtab_entry **symtab,
+				       const char *name)
+{
+	struct symtab_entry *sym = do_add_symbol(symtab, name, NULL);
+
+	if (IS_ERR(sym))
+		return NULL;
+	return sym;
+}
+
+static void free_symbols(struct symtab_entry **symtab)
+{
+	struct symtab_entry *sym = *symtab;
+	void *p;
+
+	*symtab = NULL;
+	while (sym) {
+		p = sym;
+		sym = sym->next;
+		kfree(p);
+	}
+}
+
+static int gpio_fsm_get_direction(struct gpio_chip *gc, unsigned int off)
+{
+	struct gpio_fsm *gf = gpiochip_get_data(gc);
+	struct soft_gpio *sg;
+
+	if (off >= gf->num_soft_gpios)
+		return -EINVAL;
+	sg = &gf->soft_gpios[off];
+
+	return sg->dir;
+}
+
+static int gpio_fsm_get(struct gpio_chip *gc, unsigned int off)
+{
+	struct gpio_fsm *gf = gpiochip_get_data(gc);
+	struct soft_gpio *sg;
+
+	if (off >= gf->num_soft_gpios)
+		return -EINVAL;
+	sg = &gf->soft_gpios[off];
+
+	return sg->value;
+}
+
+static void gpio_fsm_go_to_state(struct gpio_fsm *gf,
+				   struct fsm_state *new_state)
+{
+	struct input_gpio_state *inp_state;
+	struct gpio_event *gp_ev;
+	struct fsm_state *state;
+	int i;
+
+	dev_dbg(gf->dev, "go_to_state(%s)\n",
+		  new_state ? new_state->name : "<unset>");
+
+	spin_lock(&gf->spinlock);
+
+	if (gf->next_state) {
+		/* Something else has already requested a transition */
+		spin_unlock(&gf->spinlock);
+		return;
+	}
+
+	gf->next_state = new_state;
+	state = gf->current_state;
+	gf->delay_target_state = NULL;
+
+	if (state) {
+		/* Disarm any GPIO IRQs */
+		for (i = 0; i < state->num_gpio_events; i++) {
+			gp_ev = &state->gpio_events[i];
+			inp_state = &gf->input_gpio_states[gp_ev->index];
+			inp_state->target = NULL;
+		}
+	}
+
+	spin_unlock(&gf->spinlock);
+
+	if (new_state)
+		schedule_work(&gf->work);
+}
+
+static void gpio_fsm_set_soft(struct gpio_fsm *gf,
+				unsigned int off, int val)
+{
+	struct soft_gpio *sg = &gf->soft_gpios[off];
+	struct gpio_event *gp_ev;
+	struct fsm_state *state;
+	int i;
+
+	dev_dbg(gf->dev, "set(%d,%d)\n", off, val);
+	state = gf->current_state;
+	sg->value = val;
+	for (i = 0; i < state->num_soft_events; i++) {
+		gp_ev = &state->soft_events[i];
+		if (gp_ev->index == off && gp_ev->value == val) {
+			if (gf->debug)
+				dev_info(gf->dev,
+					 "GF_SOFT %d->%d -> %s\n", gp_ev->index,
+					 gp_ev->value, gp_ev->target->name);
+			gpio_fsm_go_to_state(gf, gp_ev->target);
+			break;
+		}
+	}
+}
+
+static int gpio_fsm_direction_input(struct gpio_chip *gc, unsigned int off)
+{
+	struct gpio_fsm *gf = gpiochip_get_data(gc);
+	struct soft_gpio *sg;
+
+	if (off >= gf->num_soft_gpios)
+		return -EINVAL;
+	sg = &gf->soft_gpios[off];
+	sg->dir = GPIOF_DIR_IN;
+
+	return 0;
+}
+
+static int gpio_fsm_direction_output(struct gpio_chip *gc, unsigned int off,
+				       int value)
+{
+	struct gpio_fsm *gf = gpiochip_get_data(gc);
+	struct soft_gpio *sg;
+
+	if (off >= gf->num_soft_gpios)
+		return -EINVAL;
+	sg = &gf->soft_gpios[off];
+	sg->dir = GPIOF_DIR_OUT;
+	gpio_fsm_set_soft(gf, off, value);
+
+	return 0;
+}
+
+static void gpio_fsm_set(struct gpio_chip *gc, unsigned int off, int val)
+{
+	struct gpio_fsm *gf;
+
+	gf = gpiochip_get_data(gc);
+	if (off < gf->num_soft_gpios)
+		gpio_fsm_set_soft(gf, off, val);
+}
+
+static void gpio_fsm_enter_state(struct gpio_fsm *gf,
+				   struct fsm_state *state)
+{
+	struct input_gpio_state *inp_state;
+	struct output_signal *signal;
+	struct gpio_event *event;
+	struct gpio_desc *gpiod;
+	struct soft_gpio *soft;
+	int value;
+	int i;
+
+	dev_dbg(gf->dev, "enter_state(%s)\n", state->name);
+
+	gf->current_state = state;
+
+	// 1. Apply any listed signals
+	for (i = 0; i < state->num_signals; i++) {
+		signal = &state->signals[i];
+
+		if (gf->debug)
+			dev_info(gf->dev, "  set %s %d->%d\n",
+				 (signal->type == SIGNAL_GPIO) ? "GF_OUT" :
+				 "GF_SOFT",
+				 signal->index, signal->value);
+		switch (signal->type) {
+		case SIGNAL_GPIO:
+			gpiod = gf->output_gpios->desc[signal->index];
+			gpiod_set_value_cansleep(gpiod, signal->value);
+			break;
+		case SIGNAL_SOFT:
+			soft = &gf->soft_gpios[signal->index];
+			gpio_fsm_set_soft(gf, signal->index, signal->value);
+			break;
+		}
+	}
+
+	// 2. Exit if successfully reached shutdown state
+	if (gf->shutting_down && state == state->shutdown_target) {
+		wake_up(&gf->shutdown_event);
+		return;
+	}
+
+	// 3. Schedule a timer callback if shutting down
+	if (state->shutdown_target) {
+		// Remember the absolute shutdown time in case remove is called
+		// at a later time.
+		gf->shutdown_jiffies =
+			jiffies + msecs_to_jiffies(state->shutdown_ms);
+
+		if (gf->shutting_down) {
+			gf->delay_target_state = state->shutdown_target;
+			gf->delay_ms = state->shutdown_ms;
+			mod_timer(&gf->timer, gf->shutdown_jiffies);
+		}
+	}
+
+	// During shutdown, skip everything else
+	if (gf->shutting_down)
+		return;
+
+	// Otherwise record what the shutdown time would be
+	gf->shutdown_jiffies = jiffies + msecs_to_jiffies(state->shutdown_ms);
+
+	// 4. Check soft inputs for transitions to take
+	for (i = 0; i < state->num_soft_events; i++) {
+		event = &state->soft_events[i];
+		if (gf->soft_gpios[event->index].value == event->value) {
+			if (gf->debug)
+				dev_info(gf->dev,
+					 "GF_SOFT %d=%d -> %s\n", event->index,
+					 event->value, event->target->name);
+			gpio_fsm_go_to_state(gf, event->target);
+			return;
+		}
+	}
+
+	// 5. Check GPIOs for transitions to take, enabling the IRQs
+	for (i = 0; i < state->num_gpio_events; i++) {
+		event = &state->gpio_events[i];
+		inp_state = &gf->input_gpio_states[event->index];
+		inp_state->target = event->target;
+		inp_state->value = event->value;
+		inp_state->enabled = true;
+
+		value = gpiod_get_value(gf->input_gpios->desc[event->index]);
+
+		// Clear stale event state
+		disable_irq(inp_state->irq);
+
+		irq_set_irq_type(inp_state->irq,
+				 (inp_state->value ^ inp_state->active_low) ?
+				 IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING);
+		enable_irq(inp_state->irq);
+
+		if (value == event->value && inp_state->target) {
+			if (gf->debug)
+				dev_info(gf->dev,
+					 "GF_IN %d=%d -> %s\n", event->index,
+					 event->value, event->target->name);
+			gpio_fsm_go_to_state(gf, event->target);
+			return;
+		}
+	}
+
+	// 6. Schedule a timer callback if delay_target
+	if (state->delay_target) {
+		gf->delay_target_state = state->delay_target;
+		gf->delay_ms = state->delay_ms;
+		mod_timer(&gf->timer,
+			  jiffies + msecs_to_jiffies(state->delay_ms));
+	}
+}
+
+static void gpio_fsm_work(struct work_struct *work)
+{
+	struct input_gpio_state *inp_state;
+	struct fsm_state *new_state;
+	struct fsm_state *state;
+	struct gpio_event *gp_ev;
+	struct gpio_fsm *gf;
+	int i;
+
+	gf = container_of(work, struct gpio_fsm, work);
+	spin_lock(&gf->spinlock);
+	state = gf->current_state;
+	new_state = gf->next_state;
+	if (!new_state)
+		new_state = gf->delay_target_state;
+	gf->next_state = NULL;
+	gf->delay_target_state = NULL;
+	spin_unlock(&gf->spinlock);
+
+	if (state) {
+		/* Disable any enabled GPIO IRQs */
+		for (i = 0; i < state->num_gpio_events; i++) {
+			gp_ev = &state->gpio_events[i];
+			inp_state = &gf->input_gpio_states[gp_ev->index];
+			if (inp_state->enabled) {
+				inp_state->enabled = false;
+				irq_set_irq_type(inp_state->irq,
+						 IRQF_TRIGGER_NONE);
+			}
+		}
+	}
+
+	if (new_state)
+		gpio_fsm_enter_state(gf, new_state);
+}
+
+static irqreturn_t gpio_fsm_gpio_irq_handler(int irq, void *dev_id)
+{
+	struct input_gpio_state *inp_state = dev_id;
+	struct gpio_fsm *gf = inp_state->gf;
+	struct fsm_state *target;
+
+	target = inp_state->target;
+	if (!target)
+		return IRQ_NONE;
+
+	/* If the IRQ has fired then the desired state _must_ have occurred */
+	inp_state->enabled = false;
+	irq_set_irq_type(inp_state->irq, IRQF_TRIGGER_NONE);
+	if (gf->debug)
+		dev_info(gf->dev, "GF_IN %d->%d -> %s\n",
+			 inp_state->index, inp_state->value, target->name);
+	gpio_fsm_go_to_state(gf, target);
+	return IRQ_HANDLED;
+}
+
+static void gpio_fsm_timer(struct timer_list *timer)
+{
+	struct gpio_fsm *gf = container_of(timer, struct gpio_fsm, timer);
+	struct fsm_state *target;
+
+	target = gf->delay_target_state;
+	if (!target)
+		return;
+
+	if (gf->debug)
+		dev_info(gf->dev, "GF_DELAY %d -> %s\n", gf->delay_ms,
+			 target->name);
+
+	gpio_fsm_go_to_state(gf, target);
+}
+
+int gpio_fsm_parse_signals(struct gpio_fsm *gf, struct fsm_state *state,
+			     struct property *prop)
+{
+	const __be32 *cells = prop->value;
+	struct output_signal *signal;
+	u32 io;
+	u32 type;
+	u32 index;
+	u32 value;
+	int ret = 0;
+	int i;
+
+	if (prop->length % 8) {
+		dev_err(gf->dev, "malformed set in state %s\n",
+			state->name);
+		return -EINVAL;
+	}
+
+	state->num_signals = prop->length/8;
+	state->signals = devm_kcalloc(gf->dev, state->num_signals,
+				      sizeof(struct output_signal),
+				      GFP_KERNEL);
+	for (i = 0; i < state->num_signals; i++) {
+		signal = &state->signals[i];
+		io = be32_to_cpu(cells[0]);
+		type = GF_IO_TYPE(io);
+		index = GF_IO_INDEX(io);
+		value = be32_to_cpu(cells[1]);
+
+		if (type != GF_OUT && type != GF_SOFT) {
+			dev_err(gf->dev,
+				"invalid set type %d in state %s\n",
+				type, state->name);
+			ret = -EINVAL;
+			break;
+		}
+		if (type == GF_OUT && index >= gf->num_output_gpios) {
+			dev_err(gf->dev,
+				"invalid GF_OUT number %d in state %s\n",
+				index, state->name);
+			ret = -EINVAL;
+			break;
+		}
+		if (type == GF_SOFT && index >= gf->num_soft_gpios) {
+			dev_err(gf->dev,
+				"invalid GF_SOFT number %d in state %s\n",
+				index, state->name);
+			ret = -EINVAL;
+			break;
+		}
+		if (value != 0 && value != 1) {
+			dev_err(gf->dev,
+				"invalid set value %d in state %s\n",
+				value, state->name);
+			ret = -EINVAL;
+			break;
+		}
+		signal->type = (type == GF_OUT) ? SIGNAL_GPIO : SIGNAL_SOFT;
+		signal->index = index;
+		signal->value = value;
+		cells += 2;
+	}
+
+	return ret;
+}
+
+struct gpio_event *new_event(struct gpio_event **events, int *num_events)
+{
+	int num = ++(*num_events);
+	*events = krealloc(*events, num * sizeof(struct gpio_event),
+			   GFP_KERNEL);
+	return *events ? *events + (num - 1) : NULL;
+}
+
+int gpio_fsm_parse_events(struct gpio_fsm *gf, struct fsm_state *state,
+			    struct property *prop)
+{
+	const __be32 *cells = prop->value;
+	struct symtab_entry *sym;
+	int num_cells;
+	int ret = 0;
+	int i;
+
+	if (prop->length % 8) {
+		dev_err(gf->dev,
+			"malformed transitions from state %s to state %s\n",
+			state->name, prop->name);
+		return -EINVAL;
+	}
+
+	sym = get_symbol(&gf->symtab, prop->name);
+	num_cells = prop->length / 4;
+	i = 0;
+	while (i < num_cells) {
+		struct gpio_event *gp_ev;
+		u32 event, param;
+		u32 index;
+
+		event = be32_to_cpu(cells[i++]);
+		param = be32_to_cpu(cells[i++]);
+		index = GF_IO_INDEX(event);
+
+		switch (GF_IO_TYPE(event)) {
+		case GF_IN:
+			if (index >= gf->num_input_gpios) {
+				dev_err(gf->dev,
+					"invalid GF_IN %d in transitions from state %s to state %s\n",
+					index, state->name, prop->name);
+				return -EINVAL;
+			}
+			if (param > 1) {
+				dev_err(gf->dev,
+					"invalid GF_IN value %d in transitions from state %s to state %s\n",
+					param, state->name, prop->name);
+				return -EINVAL;
+			}
+			gp_ev = new_event(&state->gpio_events,
+					  &state->num_gpio_events);
+			if (!gp_ev)
+				return -ENOMEM;
+			gp_ev->index = index;
+			gp_ev->value = param;
+			gp_ev->target = (struct fsm_state *)sym;
+			break;
+
+		case GF_SOFT:
+			if (index >= gf->num_soft_gpios) {
+				dev_err(gf->dev,
+					"invalid GF_SOFT %d in transitions from state %s to state %s\n",
+					index, state->name, prop->name);
+				return -EINVAL;
+			}
+			if (param > 1) {
+				dev_err(gf->dev,
+					"invalid GF_SOFT value %d in transitions from state %s to state %s\n",
+					param, state->name, prop->name);
+				return -EINVAL;
+			}
+			gp_ev = new_event(&state->soft_events,
+					  &state->num_soft_events);
+			if (!gp_ev)
+				return -ENOMEM;
+			gp_ev->index = index;
+			gp_ev->value = param;
+			gp_ev->target = (struct fsm_state *)sym;
+			break;
+
+		case GF_DELAY:
+			if (state->delay_target) {
+				dev_err(gf->dev,
+					"state %s has multiple GF_DELAYs\n",
+					state->name);
+				return -EINVAL;
+			}
+			state->delay_target = (struct fsm_state *)sym;
+			state->delay_ms = param;
+			break;
+
+		case GF_SHUTDOWN:
+			if (state->shutdown_target == state) {
+				dev_err(gf->dev,
+					"shutdown state %s has GF_SHUTDOWN\n",
+					state->name);
+				return -EINVAL;
+			} else if (state->shutdown_target) {
+				dev_err(gf->dev,
+					"state %s has multiple GF_SHUTDOWNs\n",
+					state->name);
+				return -EINVAL;
+			}
+			state->shutdown_target =
+				(struct fsm_state *)sym;
+			state->shutdown_ms = param;
+			break;
+
+		default:
+			dev_err(gf->dev,
+				"invalid event %08x in transitions from state %s to state %s\n",
+				event, state->name, prop->name);
+			return -EINVAL;
+		}
+	}
+	if (i != num_cells) {
+		dev_err(gf->dev,
+			"malformed transitions from state %s to state %s\n",
+			state->name, prop->name);
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+int gpio_fsm_parse_state(struct gpio_fsm *gf,
+			   struct fsm_state *state,
+			   struct device_node *np)
+{
+	struct symtab_entry *sym;
+	struct property *prop;
+	int ret;
+
+	state->name = np->name;
+	ret = add_symbol(&gf->symtab, np->name, state);
+	if (ret) {
+		switch (ret) {
+		case -EINVAL:
+			dev_err(gf->dev, "'%s' is not a valid state name\n",
+				np->name);
+			break;
+		case -EEXIST:
+			dev_err(gf->dev, "state %s already defined\n",
+				np->name);
+			break;
+		default:
+			dev_err(gf->dev, "error %d adding state %s symbol\n",
+				ret, np->name);
+			break;
+		}
+		return ret;
+	}
+
+	for_each_property_of_node(np, prop) {
+		sym = get_symbol(&gf->symtab, prop->name);
+		if (!sym) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		switch ((uintptr_t)sym->value) {
+		case SYM_SET:
+			ret = gpio_fsm_parse_signals(gf, state, prop);
+			break;
+		case SYM_START:
+			if (gf->start_state) {
+				dev_err(gf->dev, "multiple start states\n");
+				ret = -EINVAL;
+			} else {
+				gf->start_state = state;
+			}
+			break;
+		case SYM_SHUTDOWN:
+			state->shutdown_target = state;
+			gf->shutdown_state = state;
+			break;
+		case SYM_NAME:
+			/* Ignore */
+			break;
+		default:
+			/* A set of transition events to this state */
+			ret = gpio_fsm_parse_events(gf, state, prop);
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static void dump_all(struct gpio_fsm *gf)
+{
+	int i, j;
+
+	dev_info(gf->dev, "Input GPIOs:\n");
+	for (i = 0; i < gf->num_input_gpios; i++)
+		dev_info(gf->dev, "  %d: %p\n", i,
+			 gf->input_gpios->desc[i]);
+
+	dev_info(gf->dev, "Output GPIOs:\n");
+	for (i = 0; i < gf->num_output_gpios; i++)
+		dev_info(gf->dev, "  %d: %p\n", i,
+			 gf->output_gpios->desc[i]);
+
+	dev_info(gf->dev, "Soft GPIOs:\n");
+	for (i = 0; i < gf->num_soft_gpios; i++)
+		dev_info(gf->dev, "  %d: %s %d\n", i,
+			 (gf->soft_gpios[i].dir == GPIOF_DIR_IN) ? "IN" : "OUT",
+			 gf->soft_gpios[i].value);
+
+	dev_info(gf->dev, "Start state: %s\n",
+		 gf->start_state ? gf->start_state->name : "-");
+
+	dev_info(gf->dev, "Shutdown timeout: %d ms\n",
+		 gf->shutdown_timeout_ms);
+
+	for (i = 0; i < gf->num_states; i++) {
+		struct fsm_state *state = &gf->states[i];
+
+		dev_info(gf->dev, "State %s:\n", state->name);
+
+		if (state->shutdown_target == state)
+			dev_info(gf->dev, "  Shutdown state\n");
+
+		dev_info(gf->dev, "  Signals:\n");
+		for (j = 0; j < state->num_signals; j++) {
+			struct output_signal *signal = &state->signals[j];
+
+			dev_info(gf->dev, "    %d: %s %d=%d\n", j,
+				 (signal->type == SIGNAL_GPIO) ? "GPIO" :
+								 "SOFT",
+				 signal->index, signal->value);
+		}
+
+		dev_info(gf->dev, "  GPIO events:\n");
+		for (j = 0; j < state->num_gpio_events; j++) {
+			struct gpio_event *event = &state->gpio_events[j];
+
+			dev_info(gf->dev, "    %d: %d=%d -> %s\n", j,
+				 event->index, event->value,
+				 event->target->name);
+		}
+
+		dev_info(gf->dev, "  Soft events:\n");
+		for (j = 0; j < state->num_soft_events; j++) {
+			struct gpio_event *event = &state->soft_events[j];
+
+			dev_info(gf->dev, "    %d: %d=%d -> %s\n", j,
+				 event->index, event->value,
+				 event->target->name);
+		}
+
+		if (state->delay_target)
+			dev_info(gf->dev, "  Delay: %d ms -> %s\n",
+				 state->delay_ms, state->delay_target->name);
+
+		if (state->shutdown_target && state->shutdown_target != state)
+			dev_info(gf->dev, "  Shutdown: %d ms -> %s\n",
+				 state->shutdown_ms,
+				 state->shutdown_target->name);
+	}
+	dev_info(gf->dev, "\n");
+}
+
+static int resolve_sym_to_state(struct gpio_fsm *gf, struct fsm_state **pstate)
+{
+	struct symtab_entry *sym = (struct symtab_entry *)*pstate;
+
+	if (!sym)
+		return -ENOMEM;
+
+	*pstate = sym->value;
+
+	if (!*pstate) {
+		dev_err(gf->dev, "state %s not defined\n",
+			sym->name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int gpio_fsm_probe(struct platform_device *pdev)
+{
+	struct input_gpio_state *inp_state;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *cp;
+	struct gpio_fsm *gf;
+	u32 debug = 0;
+	int num_states;
+	u32 num_soft_gpios;
+	int ret;
+	int i;
+	static const char *const reserved_symbols[] = {
+		[SYM_NAME] = "name",
+		[SYM_SET] = "set",
+		[SYM_START] = "start_state",
+		[SYM_SHUTDOWN] = "shutdown_state",
+	};
+
+	if (of_property_read_u32(np, "num-soft-gpios", &num_soft_gpios)) {
+		dev_err(dev, "missing 'num-soft-gpios' property\n");
+		return -EINVAL;
+	}
+
+	of_property_read_u32(np, "debug", &debug);
+
+	gf = devm_kzalloc(dev, sizeof(*gf), GFP_KERNEL);
+	if (!gf)
+		return -ENOMEM;
+
+	gf->dev = dev;
+	gf->debug = debug;
+
+	if (of_property_read_u32(np, "shutdown-timeout-ms",
+				 &gf->shutdown_timeout_ms))
+		gf->shutdown_timeout_ms = 5000;
+
+	gf->num_soft_gpios = num_soft_gpios;
+	gf->soft_gpios = devm_kcalloc(dev, num_soft_gpios,
+				      sizeof(struct soft_gpio), GFP_KERNEL);
+	if (!gf->soft_gpios)
+		return -ENOMEM;
+	for (i = 0; i < num_soft_gpios; i++) {
+		struct soft_gpio *sg = &gf->soft_gpios[i];
+
+		sg->dir = GPIOF_DIR_IN;
+		sg->value = 0;
+	}
+
+	gf->input_gpios = devm_gpiod_get_array_optional(dev, "input", GPIOD_IN);
+	if (IS_ERR(gf->input_gpios)) {
+		ret = PTR_ERR(gf->input_gpios);
+		dev_err(dev, "failed to get input gpios from DT - %d\n", ret);
+		return ret;
+	}
+	gf->num_input_gpios = (gf->input_gpios ? gf->input_gpios->ndescs : 0);
+
+	gf->input_gpio_states = devm_kcalloc(dev, gf->num_input_gpios,
+					     sizeof(struct input_gpio_state),
+					     GFP_KERNEL);
+	if (!gf->input_gpio_states)
+		return -ENOMEM;
+	for (i = 0; i < gf->num_input_gpios; i++) {
+		inp_state = &gf->input_gpio_states[i];
+		inp_state->desc = gf->input_gpios->desc[i];
+		inp_state->gf = gf;
+		inp_state->index = i;
+		inp_state->irq = gpiod_to_irq(inp_state->desc);
+		inp_state->active_low = gpiod_is_active_low(inp_state->desc);
+		if (inp_state->irq >= 0)
+			ret = devm_request_irq(gf->dev, inp_state->irq,
+					       gpio_fsm_gpio_irq_handler,
+					       IRQF_TRIGGER_NONE,
+					       dev_name(dev),
+					       inp_state);
+		else
+			ret = inp_state->irq;
+
+		if (ret) {
+			dev_err(dev,
+				"failed to get IRQ for input gpio - %d\n",
+				ret);
+			return ret;
+		}
+	}
+
+	gf->output_gpios = devm_gpiod_get_array_optional(dev, "output",
+							 GPIOD_OUT_LOW);
+	if (IS_ERR(gf->output_gpios)) {
+		ret = PTR_ERR(gf->output_gpios);
+		dev_err(dev, "failed to get output gpios from DT - %d\n", ret);
+		return ret;
+	}
+	gf->num_output_gpios = (gf->output_gpios ? gf->output_gpios->ndescs :
+				0);
+
+	num_states = of_get_child_count(np);
+	if (!num_states) {
+		dev_err(dev, "no states declared\n");
+		return -EINVAL;
+	}
+	gf->states = devm_kcalloc(dev, num_states,
+				  sizeof(struct fsm_state), GFP_KERNEL);
+	if (!gf->states)
+		return -ENOMEM;
+
+	// add reserved words to the symbol table
+	for (i = 0; i < ARRAY_SIZE(reserved_symbols); i++) {
+		if (reserved_symbols[i])
+			add_symbol(&gf->symtab, reserved_symbols[i], (void *)i);
+	}
+
+	// parse the state
+	for_each_child_of_node(np, cp) {
+		struct fsm_state *state = &gf->states[gf->num_states];
+
+		ret = gpio_fsm_parse_state(gf, state, cp);
+		if (ret)
+			return ret;
+		gf->num_states++;
+	}
+
+	if (!gf->start_state) {
+		dev_err(gf->dev, "no start state defined\n");
+		return -EINVAL;
+	}
+
+	// resolve symbol pointers into state pointers
+	for (i = 0; !ret && i < gf->num_states; i++) {
+		struct fsm_state *state = &gf->states[i];
+		int j;
+
+		for (j = 0; !ret && j < state->num_gpio_events; j++) {
+			struct gpio_event *ev = &state->gpio_events[j];
+
+			ret = resolve_sym_to_state(gf, &ev->target);
+		}
+
+		for (j = 0; !ret && j < state->num_soft_events; j++) {
+			struct gpio_event *ev = &state->soft_events[j];
+
+			ret = resolve_sym_to_state(gf, &ev->target);
+		}
+
+		if (!ret) {
+			resolve_sym_to_state(gf, &state->delay_target);
+			if (state->shutdown_target != state)
+				resolve_sym_to_state(gf,
+						     &state->shutdown_target);
+		}
+	}
+
+	if (!ret && gf->debug > 1)
+		dump_all(gf);
+
+	free_symbols(&gf->symtab);
+
+	if (ret)
+		return ret;
+
+	gf->gc.parent = dev;
+	gf->gc.label = np->name;
+	gf->gc.owner = THIS_MODULE;
+	gf->gc.of_node = np;
+	gf->gc.base = -1;
+	gf->gc.ngpio = num_soft_gpios;
+
+	gf->gc.get_direction = gpio_fsm_get_direction;
+	gf->gc.direction_input = gpio_fsm_direction_input;
+	gf->gc.direction_output = gpio_fsm_direction_output;
+	gf->gc.get = gpio_fsm_get;
+	gf->gc.set = gpio_fsm_set;
+	gf->gc.can_sleep = true;
+	spin_lock_init(&gf->spinlock);
+	INIT_WORK(&gf->work, gpio_fsm_work);
+	timer_setup(&gf->timer, gpio_fsm_timer, 0);
+	init_waitqueue_head(&gf->shutdown_event);
+
+	platform_set_drvdata(pdev, gf);
+
+	if (gf->debug)
+		dev_info(gf->dev, "Start -> %s\n", gf->start_state->name);
+
+	gpio_fsm_go_to_state(gf, gf->start_state);
+
+	return devm_gpiochip_add_data(dev, &gf->gc, gf);
+}
+
+static int gpio_fsm_remove(struct platform_device *pdev)
+{
+	struct gpio_fsm *gf = platform_get_drvdata(pdev);
+	int i;
+
+	if (gf->shutdown_state) {
+		if (gf->debug)
+			dev_info(gf->dev, "Shutting down...\n");
+
+		spin_lock(&gf->spinlock);
+		gf->shutting_down = true;
+		if (gf->current_state->shutdown_target &&
+		    gf->current_state->shutdown_target != gf->current_state) {
+			gf->delay_target_state =
+				gf->current_state->shutdown_target;
+			mod_timer(&gf->timer, gf->shutdown_jiffies);
+		}
+		spin_unlock(&gf->spinlock);
+
+		wait_event_timeout(gf->shutdown_event,
+				   gf->current_state->shutdown_target ==
+				   gf->current_state,
+				   msecs_to_jiffies(gf->shutdown_timeout_ms));
+		if (gf->current_state->shutdown_target == gf->current_state)
+			gpio_fsm_enter_state(gf, gf->shutdown_state);
+	}
+	cancel_work_sync(&gf->work);
+	del_timer_sync(&gf->timer);
+
+	/* Events aren't allocated from managed storage */
+	for (i = 0; i < gf->num_states; i++) {
+		kfree(gf->states[i].gpio_events);
+		kfree(gf->states[i].soft_events);
+	}
+	if (gf->debug)
+		dev_info(gf->dev, "Exiting\n");
+
+	return 0;
+}
+
+static void gpio_fsm_shutdown(struct platform_device *pdev)
+{
+	gpio_fsm_remove(pdev);
+}
+
+static const struct of_device_id gpio_fsm_ids[] = {
+	{ .compatible = "rpi,gpio-fsm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_fsm_ids);
+
+static struct platform_driver gpio_fsm_driver = {
+	.driver	= {
+		.name		= MODULE_NAME,
+		.of_match_table	= of_match_ptr(gpio_fsm_ids),
+	},
+	.probe = gpio_fsm_probe,
+	.remove = gpio_fsm_remove,
+	.shutdown = gpio_fsm_shutdown,
+};
+module_platform_driver(gpio_fsm_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Phil Elwell <phil@raspberrypi.com>");
+MODULE_DESCRIPTION("GPIO FSM driver");
+MODULE_ALIAS("platform:gpio-fsm");
--- /dev/null
+++ b/include/dt-bindings/gpio/gpio-fsm.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * This header provides constants for binding rpi,gpio-fsm.
+ */
+
+#ifndef _DT_BINDINGS_GPIO_FSM_H
+#define _DT_BINDINGS_GPIO_FSM_H
+
+#define GF_IN       0
+#define GF_OUT      1
+#define GF_SOFT     2
+#define GF_DELAY    3
+#define GF_SHUTDOWN 4
+
+#define GF_IO(t, v) (((v) << 16) | ((t) & 0xffff))
+
+#define GF_IP(x)    GF_IO(GF_IN, (x))
+#define GF_OP(x)    GF_IO(GF_OUT, (x))
+#define GF_SW(x)    GF_IO(GF_SOFT, (x))
+
+#endif