drivers/clk/clk-si514.c

root/drivers/clk/clk-si514.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for Silicon Labs Si514 Programmable Oscillator
 *
 * Copyright (C) 2015 Topic Embedded Products
 *
 * Author: Mike Looijmans <mike.looijmans@topic.nl>
 */

#include <linux/clk-provider.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/regmap.h>
#include <linux/slab.h>

/* I2C registers */
#define SI514_REG_LP            0
#define SI514_REG_M_FRAC1       5
#define SI514_REG_M_FRAC2       6
#define SI514_REG_M_FRAC3       7
#define SI514_REG_M_INT_FRAC    8
#define SI514_REG_M_INT         9
#define SI514_REG_HS_DIV        10
#define SI514_REG_LS_HS_DIV     11
#define SI514_REG_OE_STATE      14
#define SI514_REG_RESET         128
#define SI514_REG_CONTROL       132

/* Register values */
#define SI514_RESET_RST         BIT(7)

#define SI514_CONTROL_FCAL      BIT(0)
#define SI514_CONTROL_OE        BIT(2)

#define SI514_MIN_FREQ      100000U
#define SI514_MAX_FREQ   250000000U

#define FXO               31980000U

#define FVCO_MIN        2080000000U
#define FVCO_MAX        2500000000U

#define HS_DIV_MAX      1022

struct clk_si514 {
        struct clk_hw hw;
        struct regmap *regmap;
        struct i2c_client *i2c_client;
};
#define to_clk_si514(_hw)       container_of(_hw, struct clk_si514, hw)

/* Multiplier/divider settings */
struct clk_si514_muldiv {
        u32 m_frac;  /* 29-bit Fractional part of multiplier M */
        u8 m_int; /* Integer part of multiplier M, 65..78 */
        u8 ls_div_bits; /* 2nd divider, as 2^x */
        u16 hs_div; /* 1st divider, must be even and 10<=x<=1022 */
};

/* Enables or disables the output driver */
static int si514_enable_output(struct clk_si514 *data, bool enable)
{
        return regmap_update_bits(data->regmap, SI514_REG_CONTROL,
                SI514_CONTROL_OE, enable ? SI514_CONTROL_OE : 0);
}

static int si514_prepare(struct clk_hw *hw)
{
        struct clk_si514 *data = to_clk_si514(hw);

        return si514_enable_output(data, true);
}

static void si514_unprepare(struct clk_hw *hw)
{
        struct clk_si514 *data = to_clk_si514(hw);

        si514_enable_output(data, false);
}

static int si514_is_prepared(struct clk_hw *hw)
{
        struct clk_si514 *data = to_clk_si514(hw);
        unsigned int val;
        int err;

        err = regmap_read(data->regmap, SI514_REG_CONTROL, &val);
        if (err < 0)
                return err;

        return !!(val & SI514_CONTROL_OE);
}

/* Retrieve clock multiplier and dividers from hardware */
static int si514_get_muldiv(struct clk_si514 *data,
        struct clk_si514_muldiv *settings)
{
        int err;
        u8 reg[7];

        err = regmap_bulk_read(data->regmap, SI514_REG_M_FRAC1,
                        reg, ARRAY_SIZE(reg));
        if (err)
                return err;

        settings->m_frac = reg[0] | reg[1] << 8 | reg[2] << 16 |
                           (reg[3] & 0x1F) << 24;
        settings->m_int = (reg[4] & 0x3f) << 3 | reg[3] >> 5;
        settings->ls_div_bits = (reg[6] >> 4) & 0x07;
        settings->hs_div = (reg[6] & 0x03) << 8 | reg[5];
        return 0;
}

static int si514_set_muldiv(struct clk_si514 *data,
        struct clk_si514_muldiv *settings)
{
        u8 lp;
        u8 reg[7];
        int err;

        /* Calculate LP1/LP2 according to table 13 in the datasheet */
        /* 65.259980246 */
        if (settings->m_int < 65 ||
                (settings->m_int == 65 && settings->m_frac <= 139575831))
                lp = 0x22;
        /* 67.859763463 */
        else if (settings->m_int < 67 ||
                (settings->m_int == 67 && settings->m_frac <= 461581994))
                lp = 0x23;
        /* 72.937624981 */
        else if (settings->m_int < 72 ||
                (settings->m_int == 72 && settings->m_frac <= 503383578))
                lp = 0x33;
        /* 75.843265046 */
        else if (settings->m_int < 75 ||
                (settings->m_int == 75 && settings->m_frac <= 452724474))
                lp = 0x34;
        else
                lp = 0x44;

        err = regmap_write(data->regmap, SI514_REG_LP, lp);
        if (err < 0)
                return err;

        reg[0] = settings->m_frac;
        reg[1] = settings->m_frac >> 8;
        reg[2] = settings->m_frac >> 16;
        reg[3] = settings->m_frac >> 24 | settings->m_int << 5;
        reg[4] = settings->m_int >> 3;
        reg[5] = settings->hs_div;
        reg[6] = (settings->hs_div >> 8) | (settings->ls_div_bits << 4);

        err = regmap_bulk_write(data->regmap, SI514_REG_HS_DIV, reg + 5, 2);
        if (err < 0)
                return err;
        /*
         * Writing to SI514_REG_M_INT_FRAC triggers the clock change, so that
         * must be written last
         */
        return regmap_bulk_write(data->regmap, SI514_REG_M_FRAC1, reg, 5);
}

/* Calculate divider settings for a given frequency */
static int si514_calc_muldiv(struct clk_si514_muldiv *settings,
        unsigned long frequency)
{
        u64 m;
        u32 ls_freq;
        u32 tmp;
        u8 res;

        if ((frequency < SI514_MIN_FREQ) || (frequency > SI514_MAX_FREQ))
                return -EINVAL;

        /* Determine the minimum value of LS_DIV and resulting target freq. */
        ls_freq = frequency;
        if (frequency >= (FVCO_MIN / HS_DIV_MAX))
                settings->ls_div_bits = 0;
        else {
                res = 1;
                tmp = 2 * HS_DIV_MAX;
                while (tmp <= (HS_DIV_MAX * 32)) {
                        if ((frequency * tmp) >= FVCO_MIN)
                                break;
                        ++res;
                        tmp <<= 1;
                }
                settings->ls_div_bits = res;
                ls_freq = frequency << res;
        }

        /* Determine minimum HS_DIV, round up to even number */
        settings->hs_div = DIV_ROUND_UP(FVCO_MIN >> 1, ls_freq) << 1;

        /* M = LS_DIV x HS_DIV x frequency / F_XO (in fixed-point) */
        m = ((u64)(ls_freq * settings->hs_div) << 29) + (FXO / 2);
        do_div(m, FXO);
        settings->m_frac = (u32)m & (BIT(29) - 1);
        settings->m_int = (u32)(m >> 29);

        return 0;
}

/* Calculate resulting frequency given the register settings */
static unsigned long si514_calc_rate(struct clk_si514_muldiv *settings)
{
        u64 m = settings->m_frac | ((u64)settings->m_int << 29);
        u32 d = settings->hs_div * BIT(settings->ls_div_bits);

        return ((u32)(((m * FXO) + (FXO / 2)) >> 29)) / d;
}

static unsigned long si514_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        struct clk_si514 *data = to_clk_si514(hw);
        struct clk_si514_muldiv settings;
        int err;

        err = si514_get_muldiv(data, &settings);
        if (err) {
                dev_err(&data->i2c_client->dev, "unable to retrieve settings\n");
                return 0;
        }

        return si514_calc_rate(&settings);
}

static int si514_determine_rate(struct clk_hw *hw,
                                struct clk_rate_request *req)
{
        struct clk_si514_muldiv settings;
        int err;

        if (!req->rate) {
                req->rate = 0;

                return 0;
        }

        err = si514_calc_muldiv(&settings, req->rate);
        if (err) {
                req->rate = err;

                return 0;
        }

        req->rate = si514_calc_rate(&settings);

        return 0;
}

/*
 * Update output frequency for big frequency changes (> 1000 ppm).
 * The chip supports <1000ppm changes "on the fly", we haven't implemented
 * that here.
 */
static int si514_set_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long parent_rate)
{
        struct clk_si514 *data = to_clk_si514(hw);
        struct clk_si514_muldiv settings;
        unsigned int old_oe_state;
        int err;

        err = si514_calc_muldiv(&settings, rate);
        if (err)
                return err;

        err = regmap_read(data->regmap, SI514_REG_CONTROL, &old_oe_state);
        if (err)
                return err;

        si514_enable_output(data, false);

        err = si514_set_muldiv(data, &settings);
        if (err < 0)
                return err; /* Undefined state now, best to leave disabled */

        /* Trigger calibration */
        err = regmap_write(data->regmap, SI514_REG_CONTROL, SI514_CONTROL_FCAL);
        if (err < 0)
                return err;

        /* Applying a new frequency can take up to 10ms */
        usleep_range(10000, 12000);

        if (old_oe_state & SI514_CONTROL_OE)
                si514_enable_output(data, true);

        return err;
}

static const struct clk_ops si514_clk_ops = {
        .prepare = si514_prepare,
        .unprepare = si514_unprepare,
        .is_prepared = si514_is_prepared,
        .recalc_rate = si514_recalc_rate,
        .determine_rate = si514_determine_rate,
        .set_rate = si514_set_rate,
};

static bool si514_regmap_is_volatile(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case SI514_REG_CONTROL:
        case SI514_REG_RESET:
                return true;
        default:
                return false;
        }
}

static bool si514_regmap_is_writeable(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case SI514_REG_LP:
        case SI514_REG_M_FRAC1 ... SI514_REG_LS_HS_DIV:
        case SI514_REG_OE_STATE:
        case SI514_REG_RESET:
        case SI514_REG_CONTROL:
                return true;
        default:
                return false;
        }
}

static const struct regmap_config si514_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .cache_type = REGCACHE_MAPLE,
        .max_register = SI514_REG_CONTROL,
        .writeable_reg = si514_regmap_is_writeable,
        .volatile_reg = si514_regmap_is_volatile,
};

static int si514_probe(struct i2c_client *client)
{
        struct clk_si514 *data;
        struct clk_init_data init;
        int err;

        data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        init.ops = &si514_clk_ops;
        init.flags = 0;
        init.num_parents = 0;
        data->hw.init = &init;
        data->i2c_client = client;

        if (of_property_read_string(client->dev.of_node, "clock-output-names",
                        &init.name))
                init.name = client->dev.of_node->name;

        data->regmap = devm_regmap_init_i2c(client, &si514_regmap_config);
        if (IS_ERR(data->regmap)) {
                dev_err(&client->dev, "failed to allocate register map\n");
                return PTR_ERR(data->regmap);
        }

        i2c_set_clientdata(client, data);

        err = devm_clk_hw_register(&client->dev, &data->hw);
        if (err) {
                dev_err(&client->dev, "clock registration failed\n");
                return err;
        }
        err = devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
                                          &data->hw);
        if (err) {
                dev_err(&client->dev, "unable to add clk provider\n");
                return err;
        }

        return 0;
}

static const struct i2c_device_id si514_id[] = {
        { "si514" },
        { }
};
MODULE_DEVICE_TABLE(i2c, si514_id);

static const struct of_device_id clk_si514_of_match[] = {
        { .compatible = "silabs,si514" },
        { },
};
MODULE_DEVICE_TABLE(of, clk_si514_of_match);

static struct i2c_driver si514_driver = {
        .driver = {
                .name = "si514",
                .of_match_table = clk_si514_of_match,
        },
        .probe          = si514_probe,
        .id_table       = si514_id,
};
module_i2c_driver(si514_driver);

MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
MODULE_DESCRIPTION("Si514 driver");
MODULE_LICENSE("GPL");
Linux
