[PATCH v5 3/8] drivers: cpuidle: implement DT based idle states infrastructure

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On most common ARM systems, the low-power states a CPU can be put into are
not discoverable in HW and require device tree bindings to describe
power down suspend operations and idle states parameters.

In order to enable DT based idle states and configure idle drivers, this
patch implements the bulk infrastructure required to parse the device tree
idle states bindings and initialize the corresponding CPUidle driver states
data.

Code that initializes idle states checks the CPU idle driver cpumask so
that multiple CPU idle drivers can be initialized through it in the
kernel. The CPU idle driver cpumask defines which idle states should be
considered valid for the driver, ie idle states that are valid on a set
of cpus the idle driver manages.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
---
 drivers/cpuidle/Kconfig          |   8 ++
 drivers/cpuidle/Makefile         |   1 +
 drivers/cpuidle/dt_idle_states.c | 283 +++++++++++++++++++++++++++++++++++++++
 drivers/cpuidle/dt_idle_states.h |   8 ++
 4 files changed, 300 insertions(+)
 create mode 100644 drivers/cpuidle/dt_idle_states.c
 create mode 100644 drivers/cpuidle/dt_idle_states.h

diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 1b96fb9..414e7a96 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -30,6 +30,14 @@ config CPU_IDLE_GOV_MENU
 	bool "Menu governor (for tickless system)"
 	default y
 
+config DT_IDLE_STATES
+        bool "Idle states DT support"
+	depends on ARM || ARM64
+	help
+	 Allows the CPU idle framework to initialize CPU idle drivers
+	 state data by using DT provided nodes compliant with idle states
+	 device tree bindings.
+
 menu "ARM CPU Idle Drivers"
 depends on ARM
 source "drivers/cpuidle/Kconfig.arm"
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index d8bb1ff..b27a062 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -4,6 +4,7 @@
 
 obj-y += cpuidle.o driver.o governor.o sysfs.o governors/
 obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
+obj-$(CONFIG_DT_IDLE_STATES)		  += dt_idle_states.o
 
 ##################################################################################
 # ARM SoC drivers
diff --git a/drivers/cpuidle/dt_idle_states.c b/drivers/cpuidle/dt_idle_states.c
new file mode 100644
index 0000000..5c16001c
--- /dev/null
+++ b/drivers/cpuidle/dt_idle_states.c
@@ -0,0 +1,283 @@
+/*
+ * DT idle states parsing code.
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) "DT idle-states: " fmt
+
+#include <linux/cpuidle.h>
+#include <linux/cpumask.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/list_sort.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#include "dt_idle_states.h"
+
+struct state_elem {
+	struct list_head list;
+	struct device_node *node;
+	u32 val;
+};
+
+static struct list_head head __initdata = LIST_HEAD_INIT(head);
+
+static bool __init state_cpu_valid(struct device_node *state_node,
+				   struct device_node *cpu_node)
+{
+	int i = 0;
+	struct device_node *cpu_state;
+
+	while ((cpu_state = of_parse_phandle(cpu_node,
+					     "cpu-idle-states", i++))) {
+		if (cpu_state && state_node == cpu_state) {
+			of_node_put(cpu_state);
+			return true;
+		}
+		of_node_put(cpu_state);
+	}
+	return false;
+}
+
+static bool __init state_cpus_valid(const cpumask_t *cpus,
+				    struct device_node *state_node)
+{
+	int cpu;
+	struct device_node *cpu_node;
+
+	/*
+	 * Check if state is valid on driver cpumask cpus
+	 */
+	for_each_cpu(cpu, cpus) {
+		cpu_node = of_get_cpu_node(cpu, NULL);
+
+		if (!cpu_node) {
+			pr_err("Missing device node for CPU %d\n", cpu);
+			return false;
+		}
+
+		if (!state_cpu_valid(state_node, cpu_node))
+			return false;
+	}
+
+	return true;
+}
+
+static int __init state_cmp(void *priv, struct list_head *a,
+			    struct list_head *b)
+{
+	struct state_elem *ela, *elb;
+
+	ela = container_of(a, struct state_elem, list);
+	elb = container_of(b, struct state_elem, list);
+
+	return ela->val - elb->val;
+}
+
+static int __init add_state_node(cpumask_t *cpumask,
+				 struct device_node *state_node)
+{
+	struct state_elem *el;
+	u32 val;
+
+	pr_debug(" * %s...\n", state_node->full_name);
+
+	if (!state_cpus_valid(cpumask, state_node))
+		return -EINVAL;
+	/*
+	 * Parse just the property required to sort the states.
+	 */
+	if (of_property_read_u32(state_node, "power-rank",
+				 &val)) {
+		pr_debug(" * %s missing power-rank property\n",
+			     state_node->full_name);
+		return -EINVAL;
+	}
+
+	el = kmalloc(sizeof(*el), GFP_KERNEL);
+	if (!el) {
+		pr_err("%s failed to allocate memory\n", __func__);
+		return -ENOMEM;
+	}
+
+	el->node = state_node;
+	el->val = val;
+	list_add_tail(&el->list, &head);
+
+	return 0;
+}
+
+static void __init init_state_node(struct cpuidle_driver *drv,
+				   struct device_node *state_node,
+				   int *cnt)
+{
+	struct cpuidle_state *idle_state;
+
+	pr_debug(" * %s...\n", state_node->full_name);
+
+	idle_state = &drv->states[*cnt];
+
+	if (of_property_read_u32(state_node, "wakeup-latency-us",
+				 &idle_state->exit_latency)) {
+		u32 entry_latency, exit_latency;
+
+		if (of_property_read_u32(state_node, "entry-latency-us",
+					 &entry_latency)) {
+			pr_debug(" * %s missing entry-latency-us property\n",
+				 state_node->full_name);
+			return;
+		}
+
+		if (of_property_read_u32(state_node, "exit-latency-us",
+					 &exit_latency)) {
+			pr_debug(" * %s missing exit-latency-us property\n",
+				 state_node->full_name);
+			return;
+		}
+		/*
+		 * If wakeup-latency-us is missing, default to entry+exit
+		 * latencies as defined in idle states bindings
+		 */
+		idle_state->exit_latency = entry_latency + exit_latency;
+	}
+
+	if (of_property_read_u32(state_node, "min-residency-us",
+				 &idle_state->target_residency)) {
+		pr_debug(" * %s missing min-residency-us property\n",
+			     state_node->full_name);
+		return;
+	}
+
+	idle_state->flags = CPUIDLE_FLAG_TIME_VALID;
+	if (!of_property_read_bool(state_node, "timer-state-retained"))
+		idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
+
+	strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN);
+	strncpy(idle_state->desc, state_node->name, CPUIDLE_NAME_LEN);
+
+	(*cnt)++;
+}
+
+static int __init init_idle_states(struct cpuidle_driver *drv,
+				   struct device_node *state_nodes[],
+				   unsigned int start_idx, bool init_nodes)
+{
+	struct state_elem *el;
+	struct list_head *curr, *tmp;
+	unsigned int cnt = start_idx;
+
+	list_for_each_entry(el, &head, list) {
+		/*
+		 * Check if the init function has to fill the
+		 * state_nodes array on behalf of the CPUidle driver.
+		 */
+		if (init_nodes)
+			state_nodes[cnt] = el->node;
+		/*
+		 * cnt is updated on return if a state was added.
+		 */
+		init_state_node(drv, el->node, &cnt);
+
+		if (cnt == CPUIDLE_STATE_MAX) {
+			pr_warn("State index reached static CPU idle state limit\n");
+			break;
+		}
+	}
+
+	drv->state_count = cnt;
+
+	list_for_each_safe(curr, tmp, &head) {
+		list_del(curr);
+		kfree(container_of(curr, struct state_elem, list));
+	}
+
+	/*
+	 * If no idle states are detected, return an error and let the idle
+	 * driver initialization fail accordingly.
+	 */
+	return (cnt > start_idx) ? 0 : -ENODATA;
+}
+
+static void __init add_idle_states(struct cpuidle_driver *drv,
+				   struct device_node *idle_states)
+{
+	struct device_node *state_node;
+
+	for_each_child_of_node(idle_states, state_node) {
+		if ((!of_device_is_compatible(state_node, "arm,idle-state"))) {
+			pr_warn(" * %s: children of /cpus/idle-states must be \"arm,idle-state\" compatible\n",
+				     state_node->full_name);
+			continue;
+		}
+		/*
+		 * If memory allocation fails, better bail out.
+		 * Initialized nodes are freed at initialization
+		 * completion in of_init_idle_driver().
+		 */
+		if ((add_state_node(drv->cpumask, state_node) == -ENOMEM))
+			break;
+	}
+	/*
+	 * Sort the states list before initializing the CPUidle driver
+	 * states array.
+	 */
+	list_sort(NULL, &head, state_cmp);
+}
+
+/**
+ * dt_init_idle_driver() - Parse the DT idle states and initialize the
+ *			   idle driver states array
+ *
+ * @drv:	  Pointer to CPU idle driver to be initialized
+ * @state_nodes:  Array of struct device_nodes to be initialized if
+ *		  init_nodes == true. Must be sized CPUIDLE_STATE_MAX
+ * @start_idx:    First idle state index to be initialized
+ * @init_nodes:   Boolean to request device nodes initialization
+ *
+ * On success the states array in the cpuidle driver contains
+ * initialized entries in the states array, starting from index start_idx.
+ * If init_nodes == true, on success the state_nodes array is initialized
+ * with idle state DT node pointers, starting from index start_idx,
+ * in a 1:1 relation with the idle driver states array.
+ *
+ * Return:
+ *	0 on success
+ *	<0 on failure
+ */
+int __init dt_init_idle_driver(struct cpuidle_driver *drv,
+			       struct device_node *state_nodes[],
+			       unsigned int start_idx, bool init_nodes)
+{
+	struct device_node *idle_states_node;
+	int ret;
+
+	if (start_idx >= CPUIDLE_STATE_MAX) {
+		pr_warn("State index exceeds static CPU idle driver states array size\n");
+		return -EINVAL;
+	}
+
+	if (WARN(init_nodes && !state_nodes,
+		"Requested nodes stashing in an invalid nodes container\n"))
+		return -EINVAL;
+
+	idle_states_node = of_find_node_by_path("/cpus/idle-states");
+	if (!idle_states_node)
+		return -ENOENT;
+
+	add_idle_states(drv, idle_states_node);
+
+	ret = init_idle_states(drv, state_nodes, start_idx, init_nodes);
+
+	of_node_put(idle_states_node);
+
+	return ret;
+}
diff --git a/drivers/cpuidle/dt_idle_states.h b/drivers/cpuidle/dt_idle_states.h
new file mode 100644
index 0000000..e74f1e8
--- /dev/null
+++ b/drivers/cpuidle/dt_idle_states.h
@@ -0,0 +1,8 @@
+#ifndef __DT_IDLE_STATES
+#define __DT_IDLE_STATES
+
+int __init dt_init_idle_driver(struct cpuidle_driver *drv,
+			       struct device_node *state_nodes[],
+			       unsigned int start_idx,
+			       bool init_nodes);
+#endif
-- 
1.9.1