/*
 * drivers/cpufreq/spear-cpufreq.c
 *
 * CPU Frequency Scaling for SPEAr platform
 *
 * Copyright (C) 2012 ST Microelectronics
 * Deepak Sikri <deepak.sikri@st.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/types.h>

/* SPEAr CPUFreq driver data structure */
static struct {
        struct clk *clk;
        unsigned int transition_latency;
        struct cpufreq_frequency_table *freq_tbl;
        u32 cnt;
} spear_cpufreq;

static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
{
        struct clk *sys_pclk;
        int pclk;
        /*
         * In SPEAr1340, cpu clk's parent sys clk can take input from
         * following sources
         */
        const char *sys_clk_src[] = {
                "sys_syn_clk",
                "pll1_clk",
                "pll2_clk",
                "pll3_clk",
        };

        /*
         * As sys clk can have multiple source with their own range
         * limitation so we choose possible sources accordingly
         */
        if (newfreq <= 300000000)
                pclk = 0; /* src is sys_syn_clk */
        else if (newfreq > 300000000 && newfreq <= 500000000)
                pclk = 3; /* src is pll3_clk */
        else if (newfreq == 600000000)
                pclk = 1; /* src is pll1_clk */
        else
                return ERR_PTR(-EINVAL);

        /* Get parent to sys clock */
        sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
        if (IS_ERR(sys_pclk))
                pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);

        return sys_pclk;
}

/*
 * In SPEAr1340, we cannot use newfreq directly because we need to actually
 * access a source clock (clk) which might not be ancestor of cpu at present.
 * Hence in SPEAr1340 we would operate on source clock directly before switching
 * cpu clock to it.
 */
static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
{
        struct clk *sys_clk;
        int ret = 0;

        sys_clk = clk_get_parent(spear_cpufreq.clk);
        if (IS_ERR(sys_clk)) {
                pr_err("failed to get cpu's parent (sys) clock\n");
                return PTR_ERR(sys_clk);
        }

        /* Set the rate of the source clock before changing the parent */
        ret = clk_set_rate(sys_pclk, newfreq);
        if (ret) {
                pr_err("Failed to set sys clk rate to %lu\n", newfreq);
                return ret;
        }

        ret = clk_set_parent(sys_clk, sys_pclk);
        if (ret) {
                pr_err("Failed to set sys clk parent\n");
                return ret;
        }

        return 0;
}

static int spear_cpufreq_target(struct cpufreq_policy *policy,
                unsigned int index)
{
        long newfreq;
        struct clk *srcclk;
        int ret, mult = 1;

        newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;

        if (of_machine_is_compatible("st,spear1340")) {
                /*
                 * SPEAr1340 is special in the sense that due to the possibility
                 * of multiple clock sources for cpu clk's parent we can have
                 * different clock source for different frequency of cpu clk.
                 * Hence we need to choose one from amongst these possible clock
                 * sources.
                 */
                srcclk = spear1340_cpu_get_possible_parent(newfreq);
                if (IS_ERR(srcclk)) {
                        pr_err("Failed to get src clk\n");
                        return PTR_ERR(srcclk);
                }

                /* SPEAr1340: src clk is always 2 * intended cpu clk */
                mult = 2;
        } else {
                /*
                 * src clock to be altered is ancestor of cpu clock. Hence we
                 * can directly work on cpu clk
                 */
                srcclk = spear_cpufreq.clk;
        }

        newfreq = clk_round_rate(srcclk, newfreq * mult);
        if (newfreq <= 0) {
                pr_err("clk_round_rate failed for cpu src clock\n");
                return newfreq;
        }

        if (mult == 2)
                ret = spear1340_set_cpu_rate(srcclk, newfreq);
        else
                ret = clk_set_rate(spear_cpufreq.clk, newfreq);

        if (ret)
                pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);

        return ret;
}

static int spear_cpufreq_init(struct cpufreq_policy *policy)
{
        policy->clk = spear_cpufreq.clk;
        return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
                        spear_cpufreq.transition_latency);
}

static struct cpufreq_driver spear_cpufreq_driver = {
        .name           = "cpufreq-spear",
        .flags          = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = spear_cpufreq_target,
        .get            = cpufreq_generic_get,
        .init           = spear_cpufreq_init,
        .attr           = cpufreq_generic_attr,
};

static int spear_cpufreq_probe(struct platform_device *pdev)
{
        struct device_node *np;
        const struct property *prop;
        struct cpufreq_frequency_table *freq_tbl;
        const __be32 *val;
        int cnt, i, ret;

        np = of_cpu_device_node_get(0);
        if (!np) {
                pr_err("No cpu node found\n");
                return -ENODEV;
        }

        if (of_property_read_u32(np, "clock-latency",
                                &spear_cpufreq.transition_latency))
                spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;

        prop = of_find_property(np, "cpufreq_tbl", NULL);
        if (!prop || !prop->value) {
                pr_err("Invalid cpufreq_tbl\n");
                ret = -ENODEV;
                goto out_put_node;
        }

        cnt = prop->length / sizeof(u32);
        val = prop->value;

        freq_tbl = kcalloc(cnt + 1, sizeof(*freq_tbl), GFP_KERNEL);
        if (!freq_tbl) {
                ret = -ENOMEM;
                goto out_put_node;
        }

        for (i = 0; i < cnt; i++)
                freq_tbl[i].frequency = be32_to_cpup(val++);

        freq_tbl[i].frequency = CPUFREQ_TABLE_END;

        spear_cpufreq.freq_tbl = freq_tbl;

        of_node_put(np);

        spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
        if (IS_ERR(spear_cpufreq.clk)) {
                pr_err("Unable to get CPU clock\n");
                ret = PTR_ERR(spear_cpufreq.clk);
                goto out_put_mem;
        }

        ret = cpufreq_register_driver(&spear_cpufreq_driver);
        if (!ret)
                return 0;

        pr_err("failed register driver: %d\n", ret);
        clk_put(spear_cpufreq.clk);

out_put_mem:
        kfree(freq_tbl);
        return ret;

out_put_node:
        of_node_put(np);
        return ret;
}

static struct platform_driver spear_cpufreq_platdrv = {
        .driver = {
                .name   = "spear-cpufreq",
        },
        .probe          = spear_cpufreq_probe,
};
module_platform_driver(spear_cpufreq_platdrv);

MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
MODULE_DESCRIPTION("SPEAr CPUFreq driver");
MODULE_LICENSE("GPL");