/*
 * Hi6220 stub clock driver
 *
 * Copyright (c) 2015 Hisilicon Limited.
 * Copyright (c) 2015 Linaro Limited.
 *
 * Author: Leo Yan <leo.yan@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.
 *
 */

#include <linux/clk-provider.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/mailbox_client.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/regmap.h>

/* Stub clocks id */
#define HI6220_STUB_ACPU0               0
#define HI6220_STUB_ACPU1               1
#define HI6220_STUB_GPU                 2
#define HI6220_STUB_DDR                 5

/* Mailbox message */
#define HI6220_MBOX_MSG_LEN             8

#define HI6220_MBOX_FREQ                0xA
#define HI6220_MBOX_CMD_SET             0x3
#define HI6220_MBOX_OBJ_AP              0x0

/* CPU dynamic frequency scaling */
#define ACPU_DFS_FREQ_MAX               0x1724
#define ACPU_DFS_CUR_FREQ               0x17CC
#define ACPU_DFS_FLAG                   0x1B30
#define ACPU_DFS_FREQ_REQ               0x1B34
#define ACPU_DFS_FREQ_LMT               0x1B38
#define ACPU_DFS_LOCK_FLAG              0xAEAEAEAE

#define to_stub_clk(hw) container_of(hw, struct hi6220_stub_clk, hw)

struct hi6220_stub_clk {
        u32 id;

        struct device *dev;
        struct clk_hw hw;

        struct regmap *dfs_map;
        struct mbox_client cl;
        struct mbox_chan *mbox;
};

struct hi6220_mbox_msg {
        unsigned char type;
        unsigned char cmd;
        unsigned char obj;
        unsigned char src;
        unsigned char para[4];
};

union hi6220_mbox_data {
        unsigned int data[HI6220_MBOX_MSG_LEN];
        struct hi6220_mbox_msg msg;
};

static unsigned int hi6220_acpu_get_freq(struct hi6220_stub_clk *stub_clk)
{
        unsigned int freq;

        regmap_read(stub_clk->dfs_map, ACPU_DFS_CUR_FREQ, &freq);
        return freq;
}

static int hi6220_acpu_set_freq(struct hi6220_stub_clk *stub_clk,
                                unsigned int freq)
{
        union hi6220_mbox_data data;

        /* set the frequency in sram */
        regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_REQ, freq);

        /* compound mailbox message */
        data.msg.type = HI6220_MBOX_FREQ;
        data.msg.cmd  = HI6220_MBOX_CMD_SET;
        data.msg.obj  = HI6220_MBOX_OBJ_AP;
        data.msg.src  = HI6220_MBOX_OBJ_AP;

        mbox_send_message(stub_clk->mbox, &data);
        return 0;
}

static int hi6220_acpu_round_freq(struct hi6220_stub_clk *stub_clk,
                                  unsigned int freq)
{
        unsigned int limit_flag, limit_freq = UINT_MAX;
        unsigned int max_freq;

        /* check the constrained frequency */
        regmap_read(stub_clk->dfs_map, ACPU_DFS_FLAG, &limit_flag);
        if (limit_flag == ACPU_DFS_LOCK_FLAG)
                regmap_read(stub_clk->dfs_map, ACPU_DFS_FREQ_LMT, &limit_freq);

        /* check the supported maximum frequency */
        regmap_read(stub_clk->dfs_map, ACPU_DFS_FREQ_MAX, &max_freq);

        /* calculate the real maximum frequency */
        max_freq = min(max_freq, limit_freq);

        if (WARN_ON(freq > max_freq))
                freq = max_freq;

        return freq;
}

static unsigned long hi6220_stub_clk_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        u32 rate = 0;
        struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);

        switch (stub_clk->id) {
        case HI6220_STUB_ACPU0:
                rate = hi6220_acpu_get_freq(stub_clk);

                /* convert from kHz to Hz */
                rate *= 1000;
                break;

        default:
                dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
                        __func__, stub_clk->id);
                break;
        }

        return rate;
}

static int hi6220_stub_clk_set_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long parent_rate)
{
        struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);
        unsigned long new_rate = rate / 1000;  /* kHz */
        int ret = 0;

        switch (stub_clk->id) {
        case HI6220_STUB_ACPU0:
                ret = hi6220_acpu_set_freq(stub_clk, new_rate);
                if (ret < 0)
                        return ret;

                break;

        default:
                dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
                        __func__, stub_clk->id);
                break;
        }

        pr_debug("%s: set rate=%ldkHz\n", __func__, new_rate);
        return ret;
}

static long hi6220_stub_clk_round_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long *parent_rate)
{
        struct hi6220_stub_clk *stub_clk = to_stub_clk(hw);
        unsigned long new_rate = rate / 1000;  /* kHz */

        switch (stub_clk->id) {
        case HI6220_STUB_ACPU0:
                new_rate = hi6220_acpu_round_freq(stub_clk, new_rate);

                /* convert from kHz to Hz */
                new_rate *= 1000;
                break;

        default:
                dev_err(stub_clk->dev, "%s: un-supported clock id %d\n",
                        __func__, stub_clk->id);
                break;
        }

        return new_rate;
}

static const struct clk_ops hi6220_stub_clk_ops = {
        .recalc_rate    = hi6220_stub_clk_recalc_rate,
        .round_rate     = hi6220_stub_clk_round_rate,
        .set_rate       = hi6220_stub_clk_set_rate,
};

static int hi6220_stub_clk_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct clk_init_data init;
        struct hi6220_stub_clk *stub_clk;
        struct clk *clk;
        struct device_node *np = pdev->dev.of_node;
        int ret;

        stub_clk = devm_kzalloc(dev, sizeof(*stub_clk), GFP_KERNEL);
        if (!stub_clk)
                return -ENOMEM;

        stub_clk->dfs_map = syscon_regmap_lookup_by_phandle(np,
                                "hisilicon,hi6220-clk-sram");
        if (IS_ERR(stub_clk->dfs_map)) {
                dev_err(dev, "failed to get sram regmap\n");
                return PTR_ERR(stub_clk->dfs_map);
        }

        stub_clk->hw.init = &init;
        stub_clk->dev = dev;
        stub_clk->id = HI6220_STUB_ACPU0;

        /* Use mailbox client with blocking mode */
        stub_clk->cl.dev = dev;
        stub_clk->cl.tx_done = NULL;
        stub_clk->cl.tx_block = true;
        stub_clk->cl.tx_tout = 500;
        stub_clk->cl.knows_txdone = false;

        /* Allocate mailbox channel */
        stub_clk->mbox = mbox_request_channel(&stub_clk->cl, 0);
        if (IS_ERR(stub_clk->mbox)) {
                dev_err(dev, "failed get mailbox channel\n");
                return PTR_ERR(stub_clk->mbox);
        }

        init.name = "acpu0";
        init.ops = &hi6220_stub_clk_ops;
        init.num_parents = 0;
        init.flags = 0;

        clk = devm_clk_register(dev, &stub_clk->hw);
        if (IS_ERR(clk))
                return PTR_ERR(clk);

        ret = of_clk_add_provider(np, of_clk_src_simple_get, clk);
        if (ret) {
                dev_err(dev, "failed to register OF clock provider\n");
                return ret;
        }

        /* initialize buffer to zero */
        regmap_write(stub_clk->dfs_map, ACPU_DFS_FLAG, 0x0);
        regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_REQ, 0x0);
        regmap_write(stub_clk->dfs_map, ACPU_DFS_FREQ_LMT, 0x0);

        dev_dbg(dev, "Registered clock '%s'\n", init.name);
        return 0;
}

static const struct of_device_id hi6220_stub_clk_of_match[] = {
        { .compatible = "hisilicon,hi6220-stub-clk", },
        {}
};

static struct platform_driver hi6220_stub_clk_driver = {
        .driver = {
                .name = "hi6220-stub-clk",
                .of_match_table = hi6220_stub_clk_of_match,
        },
        .probe = hi6220_stub_clk_probe,
};

static int __init hi6220_stub_clk_init(void)
{
        return platform_driver_register(&hi6220_stub_clk_driver);
}
subsys_initcall(hi6220_stub_clk_init);