/*
 * 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/module.h>
#include <linux/of.h>
#include <linux/of_device.h>

#include "dt_idle_states.h"

static int init_state_node(struct cpuidle_state *idle_state,
                           const struct of_device_id *matches,
                           struct device_node *state_node)
{
        int err;
        const struct of_device_id *match_id;
        const char *desc;

        match_id = of_match_node(matches, state_node);
        if (!match_id)
                return -ENODEV;
        /*
         * CPUidle drivers are expected to initialize the const void *data
         * pointer of the passed in struct of_device_id array to the idle
         * state enter function.
         */
        idle_state->enter = match_id->data;
        /*
         * Since this is not a "coupled" state, it's safe to assume interrupts
         * won't be enabled when it exits allowing the tick to be frozen
         * safely. So enter() can be also enter_s2idle() callback.
         */
        idle_state->enter_s2idle = match_id->data;

        err = of_property_read_u32(state_node, "wakeup-latency-us",
                                   &idle_state->exit_latency);
        if (err) {
                u32 entry_latency, exit_latency;

                err = of_property_read_u32(state_node, "entry-latency-us",
                                           &entry_latency);
                if (err) {
                        pr_debug(" * %pOF missing entry-latency-us property\n",
                                 state_node);
                        return -EINVAL;
                }

                err = of_property_read_u32(state_node, "exit-latency-us",
                                           &exit_latency);
                if (err) {
                        pr_debug(" * %pOF missing exit-latency-us property\n",
                                 state_node);
                        return -EINVAL;
                }
                /*
                 * 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;
        }

        err = of_property_read_u32(state_node, "min-residency-us",
                                   &idle_state->target_residency);
        if (err) {
                pr_debug(" * %pOF missing min-residency-us property\n",
                             state_node);
                return -EINVAL;
        }

        err = of_property_read_string(state_node, "idle-state-name", &desc);
        if (err)
                desc = state_node->name;

        idle_state->flags = 0;
        if (of_property_read_bool(state_node, "local-timer-stop"))
                idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
        /*
         * TODO:
         *      replace with kstrdup and pointer assignment when name
         *      and desc become string pointers
         */
        strncpy(idle_state->name, state_node->name, CPUIDLE_NAME_LEN - 1);
        strncpy(idle_state->desc, desc, CPUIDLE_DESC_LEN - 1);
        return 0;
}

/*
 * Check that the idle state is uniform across all CPUs in the CPUidle driver
 * cpumask
 */
static bool idle_state_valid(struct device_node *state_node, unsigned int idx,
                             const cpumask_t *cpumask)
{
        int cpu;
        struct device_node *cpu_node, *curr_state_node;
        bool valid = true;

        /*
         * Compare idle state phandles for index idx on all CPUs in the
         * CPUidle driver cpumask. Start from next logical cpu following
         * cpumask_first(cpumask) since that's the CPU state_node was
         * retrieved from. If a mismatch is found bail out straight
         * away since we certainly hit a firmware misconfiguration.
         */
        for (cpu = cpumask_next(cpumask_first(cpumask), cpumask);
             cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpumask)) {
                cpu_node = of_cpu_device_node_get(cpu);
                curr_state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
                                                   idx);
                if (state_node != curr_state_node)
                        valid = false;

                of_node_put(curr_state_node);
                of_node_put(cpu_node);
                if (!valid)
                        break;
        }

        return valid;
}

/**
 * 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
 * @matches:      Array of of_device_id match structures to search in for
 *                compatible idle state nodes. The data pointer for each valid
 *                struct of_device_id entry in the matches array must point to
 *                a function with the following signature, that corresponds to
 *                the CPUidle state enter function signature:
 *
 *                int (*)(struct cpuidle_device *dev,
 *                        struct cpuidle_driver *drv,
 *                        int index);
 *
 * @start_idx:    First idle state index to be initialized
 *
 * If DT idle states are detected and are valid the state count and states
 * array entries in the cpuidle driver are initialized accordingly starting
 * from index start_idx.
 *
 * Return: number of valid DT idle states parsed, <0 on failure
 */
int dt_init_idle_driver(struct cpuidle_driver *drv,
                        const struct of_device_id *matches,
                        unsigned int start_idx)
{
        struct cpuidle_state *idle_state;
        struct device_node *state_node, *cpu_node;
        int i, err = 0;
        const cpumask_t *cpumask;
        unsigned int state_idx = start_idx;

        if (state_idx >= CPUIDLE_STATE_MAX)
                return -EINVAL;
        /*
         * We get the idle states for the first logical cpu in the
         * driver mask (or cpu_possible_mask if the driver cpumask is not set)
         * and we check through idle_state_valid() if they are uniform
         * across CPUs, otherwise we hit a firmware misconfiguration.
         */
        cpumask = drv->cpumask ? : cpu_possible_mask;
        cpu_node = of_cpu_device_node_get(cpumask_first(cpumask));

        for (i = 0; ; i++) {
                state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
                if (!state_node)
                        break;

                if (!of_device_is_available(state_node)) {
                        of_node_put(state_node);
                        continue;
                }

                if (!idle_state_valid(state_node, i, cpumask)) {
                        pr_warn("%pOF idle state not valid, bailing out\n",
                                state_node);
                        err = -EINVAL;
                        break;
                }

                if (state_idx == CPUIDLE_STATE_MAX) {
                        pr_warn("State index reached static CPU idle driver states array size\n");
                        break;
                }

                idle_state = &drv->states[state_idx++];
                err = init_state_node(idle_state, matches, state_node);
                if (err) {
                        pr_err("Parsing idle state node %pOF failed with err %d\n",
                               state_node, err);
                        err = -EINVAL;
                        break;
                }
                of_node_put(state_node);
        }

        of_node_put(state_node);
        of_node_put(cpu_node);
        if (err)
                return err;
        /*
         * Update the driver state count only if some valid DT idle states
         * were detected
         */
        if (i)
                drv->state_count = state_idx;

        /*
         * Return the number of present and valid DT idle states, which can
         * also be 0 on platforms with missing DT idle states or legacy DT
         * configuration predating the DT idle states bindings.
         */
        return i;
}
EXPORT_SYMBOL_GPL(dt_init_idle_driver);