/*
 * Copyright (c) 2013 ARM/Linaro
 *
 * Authors: Daniel Lezcano <daniel.lezcano@linaro.org>
 *          Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
 *          Nicolas Pitre <nicolas.pitre@linaro.org>
 *
 * 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.
 *
 * Maintainer: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
 * Maintainer: Daniel Lezcano <daniel.lezcano@linaro.org>
 */
#include <linux/cpuidle.h>
#include <linux/cpu_pm.h>
#include <linux/slab.h>
#include <linux/of.h>

#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpuidle.h>
#include <asm/mcpm.h>
#include <asm/smp_plat.h>
#include <asm/suspend.h>

#include "dt_idle_states.h"

static int bl_enter_powerdown(struct cpuidle_device *dev,
                              struct cpuidle_driver *drv, int idx);

/*
 * NB: Owing to current menu governor behaviour big and LITTLE
 * index 1 states have to define exit_latency and target_residency for
 * cluster state since, when all CPUs in a cluster hit it, the cluster
 * can be shutdown. This means that when a single CPU enters this state
 * the exit_latency and target_residency values are somewhat overkill.
 * There is no notion of cluster states in the menu governor, so CPUs
 * have to define CPU states where possibly the cluster will be shutdown
 * depending on the state of other CPUs. idle states entry and exit happen
 * at random times; however the cluster state provides target_residency
 * values as if all CPUs in a cluster enter the state at once; this is
 * somewhat optimistic and behaviour should be fixed either in the governor
 * or in the MCPM back-ends.
 * To make this driver 100% generic the number of states and the exit_latency
 * target_residency values must be obtained from device tree bindings.
 *
 * exit_latency: refers to the TC2 vexpress test chip and depends on the
 * current cluster operating point. It is the time it takes to get the CPU
 * up and running when the CPU is powered up on cluster wake-up from shutdown.
 * Current values for big and LITTLE clusters are provided for clusters
 * running at default operating points.
 *
 * target_residency: it is the minimum amount of time the cluster has
 * to be down to break even in terms of power consumption. cluster
 * shutdown has inherent dynamic power costs (L2 writebacks to DRAM
 * being the main factor) that depend on the current operating points.
 * The current values for both clusters are provided for a CPU whose half
 * of L2 lines are dirty and require cleaning to DRAM, and takes into
 * account leakage static power values related to the vexpress TC2 testchip.
 */
static struct cpuidle_driver bl_idle_little_driver = {
        .name = "little_idle",
        .owner = THIS_MODULE,
        .states[0] = ARM_CPUIDLE_WFI_STATE,
        .states[1] = {
                .enter                  = bl_enter_powerdown,
                .exit_latency           = 700,
                .target_residency       = 2500,
                .flags                  = CPUIDLE_FLAG_TIMER_STOP,
                .name                   = "C1",
                .desc                   = "ARM little-cluster power down",
        },
        .state_count = 2,
};

static const struct of_device_id bl_idle_state_match[] __initconst = {
        { .compatible = "arm,idle-state",
          .data = bl_enter_powerdown },
        { },
};

static struct cpuidle_driver bl_idle_big_driver = {
        .name = "big_idle",
        .owner = THIS_MODULE,
        .states[0] = ARM_CPUIDLE_WFI_STATE,
        .states[1] = {
                .enter                  = bl_enter_powerdown,
                .exit_latency           = 500,
                .target_residency       = 2000,
                .flags                  = CPUIDLE_FLAG_TIMER_STOP,
                .name                   = "C1",
                .desc                   = "ARM big-cluster power down",
        },
        .state_count = 2,
};

/*
 * notrace prevents trace shims from getting inserted where they
 * should not. Global jumps and ldrex/strex must not be inserted
 * in power down sequences where caches and MMU may be turned off.
 */
static int notrace bl_powerdown_finisher(unsigned long arg)
{
        /* MCPM works with HW CPU identifiers */
        unsigned int mpidr = read_cpuid_mpidr();
        unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
        unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);

        mcpm_set_entry_vector(cpu, cluster, cpu_resume);
        mcpm_cpu_suspend();

        /* return value != 0 means failure */
        return 1;
}

/**
 * bl_enter_powerdown - Programs CPU to enter the specified state
 * @dev: cpuidle device
 * @drv: The target state to be programmed
 * @idx: state index
 *
 * Called from the CPUidle framework to program the device to the
 * specified target state selected by the governor.
 */
static int bl_enter_powerdown(struct cpuidle_device *dev,
                                struct cpuidle_driver *drv, int idx)
{
        cpu_pm_enter();

        cpu_suspend(0, bl_powerdown_finisher);

        /* signals the MCPM core that CPU is out of low power state */
        mcpm_cpu_powered_up();

        cpu_pm_exit();

        return idx;
}

static int __init bl_idle_driver_init(struct cpuidle_driver *drv, int part_id)
{
        struct cpumask *cpumask;
        int cpu;

        cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
        if (!cpumask)
                return -ENOMEM;

        for_each_possible_cpu(cpu)
                if (smp_cpuid_part(cpu) == part_id)
                        cpumask_set_cpu(cpu, cpumask);

        drv->cpumask = cpumask;

        return 0;
}

static const struct of_device_id compatible_machine_match[] = {
        { .compatible = "arm,vexpress,v2p-ca15_a7" },
        { .compatible = "samsung,exynos5420" },
        { .compatible = "samsung,exynos5800" },
        {},
};

static int __init bl_idle_init(void)
{
        int ret;
        struct device_node *root = of_find_node_by_path("/");

        if (!root)
                return -ENODEV;

        /*
         * Initialize the driver just for a compliant set of machines
         */
        if (!of_match_node(compatible_machine_match, root))
                return -ENODEV;

        if (!mcpm_is_available())
                return -EUNATCH;

        /*
         * For now the differentiation between little and big cores
         * is based on the part number. A7 cores are considered little
         * cores, A15 are considered big cores. This distinction may
         * evolve in the future with a more generic matching approach.
         */
        ret = bl_idle_driver_init(&bl_idle_little_driver,
                                  ARM_CPU_PART_CORTEX_A7);
        if (ret)
                return ret;

        ret = bl_idle_driver_init(&bl_idle_big_driver, ARM_CPU_PART_CORTEX_A15);
        if (ret)
                goto out_uninit_little;

        /* Start at index 1, index 0 standard WFI */
        ret = dt_init_idle_driver(&bl_idle_big_driver, bl_idle_state_match, 1);
        if (ret < 0)
                goto out_uninit_big;

        /* Start at index 1, index 0 standard WFI */
        ret = dt_init_idle_driver(&bl_idle_little_driver,
                                  bl_idle_state_match, 1);
        if (ret < 0)
                goto out_uninit_big;

        ret = cpuidle_register(&bl_idle_little_driver, NULL);
        if (ret)
                goto out_uninit_big;

        ret = cpuidle_register(&bl_idle_big_driver, NULL);
        if (ret)
                goto out_unregister_little;

        return 0;

out_unregister_little:
        cpuidle_unregister(&bl_idle_little_driver);
out_uninit_big:
        kfree(bl_idle_big_driver.cpumask);
out_uninit_little:
        kfree(bl_idle_little_driver.cpumask);

        return ret;
}
device_initcall(bl_idle_init);