drivers/clk/clk-si570.c

root/drivers/clk/clk-si570.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
 *
 * Copyright (C) 2010, 2011 Ericsson AB.
 * Copyright (C) 2011 Guenter Roeck.
 * Copyright (C) 2011 - 2021 Xilinx Inc.
 *
 * Author: Guenter Roeck <guenter.roeck@ericsson.com>
 *         Sören Brinkmann <soren.brinkmann@xilinx.com>
 */

#include <linux/clk.h>
#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>

/* Si570 registers */
#define SI570_REG_HS_N1         7
#define SI570_REG_N1_RFREQ0     8
#define SI570_REG_RFREQ1        9
#define SI570_REG_RFREQ2        10
#define SI570_REG_RFREQ3        11
#define SI570_REG_RFREQ4        12
#define SI570_REG_CONTROL       135
#define SI570_REG_FREEZE_DCO    137
#define SI570_DIV_OFFSET_7PPM   6

#define HS_DIV_SHIFT            5
#define HS_DIV_MASK             0xe0
#define HS_DIV_OFFSET           4
#define N1_6_2_MASK             0x1f
#define N1_1_0_MASK             0xc0
#define RFREQ_37_32_MASK        0x3f

#define SI570_MIN_FREQ          10000000L
#define SI570_MAX_FREQ          1417500000L
#define SI598_MAX_FREQ          525000000L

#define FDCO_MIN                4850000000LL
#define FDCO_MAX                5670000000LL

#define SI570_CNTRL_RECALL      (1 << 0)
#define SI570_CNTRL_FREEZE_M    (1 << 5)
#define SI570_CNTRL_NEWFREQ     (1 << 6)

#define SI570_FREEZE_DCO        (1 << 4)

/**
 * struct clk_si570_info:
 * @max_freq:   Maximum frequency for this device
 * @has_temperature_stability: Device support temperature stability
 */
struct clk_si570_info {
        u64 max_freq;
        bool has_temperature_stability;
};

/**
 * struct clk_si570:
 * @hw: Clock hw struct
 * @regmap:     Device's regmap
 * @div_offset: Register offset for dividers
 * @info:       Device info
 * @fxtal:      Factory xtal frequency
 * @n1:         Clock divider N1
 * @hs_div:     Clock divider HSDIV
 * @rfreq:      Clock multiplier RFREQ
 * @frequency:  Current output frequency
 * @i2c_client: I2C client pointer
 */
struct clk_si570 {
        struct clk_hw hw;
        struct regmap *regmap;
        unsigned int div_offset;
        const struct clk_si570_info *info;
        u64 fxtal;
        unsigned int n1;
        unsigned int hs_div;
        u64 rfreq;
        u64 frequency;
        struct i2c_client *i2c_client;
};
#define to_clk_si570(_hw)       container_of(_hw, struct clk_si570, hw)

/**
 * si570_get_divs() - Read clock dividers from HW
 * @data:       Pointer to struct clk_si570
 * @rfreq:      Fractional multiplier (output)
 * @n1:         Divider N1 (output)
 * @hs_div:     Divider HSDIV (output)
 * Returns 0 on success, negative errno otherwise.
 *
 * Retrieve clock dividers and multipliers from the HW.
 */
static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
                unsigned int *n1, unsigned int *hs_div)
{
        int err;
        u8 reg[6];
        u64 tmp;

        err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
                        reg, ARRAY_SIZE(reg));
        if (err)
                return err;

        *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
        *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
        /* Handle invalid cases */
        if (*n1 > 1)
                *n1 &= ~1;

        tmp = reg[1] & RFREQ_37_32_MASK;
        tmp = (tmp << 8) + reg[2];
        tmp = (tmp << 8) + reg[3];
        tmp = (tmp << 8) + reg[4];
        tmp = (tmp << 8) + reg[5];
        *rfreq = tmp;

        return 0;
}

/**
 * si570_get_defaults() - Get default values
 * @data:       Driver data structure
 * @fout:       Factory frequency output
 * @skip_recall:        If true, don't recall NVM into RAM
 * Returns 0 on success, negative errno otherwise.
 */
static int si570_get_defaults(struct clk_si570 *data, u64 fout,
                              bool skip_recall)
{
        int err;
        u64 fdco;

        if (!skip_recall)
                regmap_write(data->regmap, SI570_REG_CONTROL,
                             SI570_CNTRL_RECALL);

        err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
        if (err)
                return err;

        /*
         * Accept optional precision loss to avoid arithmetic overflows.
         * Acceptable per Silicon Labs Application Note AN334.
         */
        fdco = fout * data->n1 * data->hs_div;
        if (fdco >= (1LL << 36))
                data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
        else
                data->fxtal = div64_u64(fdco << 28, data->rfreq);

        data->frequency = fout;

        return 0;
}

/**
 * si570_update_rfreq() - Update clock multiplier
 * @data:       Driver data structure
 * Passes on regmap_bulk_write() return value.
 */
static int si570_update_rfreq(struct clk_si570 *data)
{
        u8 reg[5];

        reg[0] = ((data->n1 - 1) << 6) |
                ((data->rfreq >> 32) & RFREQ_37_32_MASK);
        reg[1] = (data->rfreq >> 24) & 0xff;
        reg[2] = (data->rfreq >> 16) & 0xff;
        reg[3] = (data->rfreq >> 8) & 0xff;
        reg[4] = data->rfreq & 0xff;

        return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
                        data->div_offset, reg, ARRAY_SIZE(reg));
}

/**
 * si570_calc_divs() - Calculate clock dividers
 * @frequency:  Target frequency
 * @data:       Driver data structure
 * @out_rfreq:  RFREG fractional multiplier (output)
 * @out_n1:     Clock divider N1 (output)
 * @out_hs_div: Clock divider HSDIV (output)
 * Returns 0 on success, negative errno otherwise.
 *
 * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
 * (@out_rfreq) for a given target @frequency.
 */
static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
                u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
{
        int i;
        unsigned int n1, hs_div;
        u64 fdco, best_fdco = ULLONG_MAX;
        static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };

        for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
                hs_div = si570_hs_div_values[i];
                /* Calculate lowest possible value for n1 */
                n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
                if (!n1 || (n1 & 1))
                        n1++;
                while (n1 <= 128) {
                        fdco = (u64)frequency * (u64)hs_div * (u64)n1;
                        if (fdco > FDCO_MAX)
                                break;
                        if (fdco >= FDCO_MIN && fdco < best_fdco) {
                                *out_n1 = n1;
                                *out_hs_div = hs_div;
                                *out_rfreq = div64_u64(fdco << 28, data->fxtal);
                                best_fdco = fdco;
                        }
                        n1 += (n1 == 1 ? 1 : 2);
                }
        }

        if (best_fdco == ULLONG_MAX)
                return -EINVAL;

        return 0;
}

static unsigned long si570_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
{
        int err;
        u64 rfreq, rate;
        unsigned int n1, hs_div;
        struct clk_si570 *data = to_clk_si570(hw);

        err = si570_get_divs(data, &rfreq, &n1, &hs_div);
        if (err) {
                dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
                return data->frequency;
        }

        rfreq = div_u64(rfreq, hs_div * n1);
        rate = (data->fxtal * rfreq) >> 28;

        return rate;
}

static int si570_determine_rate(struct clk_hw *hw,
                                struct clk_rate_request *req)
{
        int err;
        u64 rfreq;
        unsigned int n1, hs_div;
        struct clk_si570 *data = to_clk_si570(hw);

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

                return 0;
        }

        if (div64_u64(abs(req->rate - data->frequency) * 10000LL,
                                data->frequency) < 35) {
                rfreq = div64_u64((data->rfreq * req->rate) +
                                  div64_u64(data->frequency, 2),
                                  data->frequency);
                n1 = data->n1;
                hs_div = data->hs_div;

        } else {
                err = si570_calc_divs(req->rate, data, &rfreq, &n1, &hs_div);
                if (err) {
                        dev_err(&data->i2c_client->dev,
                                        "unable to round rate\n");
                        req->rate = 0;

                        return 0;
                }
        }

        return 0;
}

/**
 * si570_set_frequency() - Adjust output frequency
 * @data:       Driver data structure
 * @frequency:  Target frequency
 * Returns 0 on success.
 *
 * Update output frequency for big frequency changes (> 3,500 ppm).
 */
static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
{
        int err;

        err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
                        &data->hs_div);
        if (err)
                return err;

        /*
         * The DCO reg should be accessed with a read-modify-write operation
         * per AN334
         */
        regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
        regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
                        ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
                        (((data->n1 - 1) >> 2) & N1_6_2_MASK));
        si570_update_rfreq(data);
        regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
        regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);

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

        return 0;
}

/**
 * si570_set_frequency_small() - Adjust output frequency
 * @data:       Driver data structure
 * @frequency:  Target frequency
 * Returns 0 on success.
 *
 * Update output frequency for small frequency changes (< 3,500 ppm).
 */
static int si570_set_frequency_small(struct clk_si570 *data,
                                     unsigned long frequency)
{
        /*
         * This is a re-implementation of DIV_ROUND_CLOSEST
         * using the div64_u64 function lieu of letting the compiler
         * insert EABI calls
         */
        data->rfreq = div64_u64((data->rfreq * frequency) +
                        div_u64(data->frequency, 2), data->frequency);
        regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
        si570_update_rfreq(data);
        regmap_write(data->regmap, SI570_REG_CONTROL, 0);

        /* Applying a new frequency (small change) can take up to 100us */
        usleep_range(100, 200);

        return 0;
}

static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
                unsigned long parent_rate)
{
        struct clk_si570 *data = to_clk_si570(hw);
        struct i2c_client *client = data->i2c_client;
        int err;

        if (rate < SI570_MIN_FREQ || rate > data->info->max_freq) {
                dev_err(&client->dev,
                        "requested frequency %lu Hz is out of range\n", rate);
                return -EINVAL;
        }

        if (div64_u64(abs(rate - data->frequency) * 10000LL,
                                data->frequency) < 35)
                err = si570_set_frequency_small(data, rate);
        else
                err = si570_set_frequency(data, rate);

        if (err)
                return err;

        data->frequency = rate;

        return 0;
}

static const struct clk_ops si570_clk_ops = {
        .recalc_rate = si570_recalc_rate,
        .determine_rate = si570_determine_rate,
        .set_rate = si570_set_rate,
};

static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case SI570_REG_CONTROL:
                return true;
        default:
                return false;
        }
}

static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
        case SI570_REG_CONTROL:
        case SI570_REG_FREEZE_DCO:
                return true;
        default:
                return false;
        }
}

static const struct regmap_config si570_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .cache_type = REGCACHE_MAPLE,
        .max_register = 137,
        .writeable_reg = si570_regmap_is_writeable,
        .volatile_reg = si570_regmap_is_volatile,
};

static int si570_probe(struct i2c_client *client)
{
        struct clk_si570 *data;
        struct clk_init_data init;
        u32 initial_fout, factory_fout, stability;
        bool skip_recall;
        int err;

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

        init.ops = &si570_clk_ops;
        init.flags = 0;
        init.num_parents = 0;
        data->hw.init = &init;
        data->i2c_client = client;

        data->info = i2c_get_match_data(client);
        if (data->info->has_temperature_stability) {
                err = of_property_read_u32(client->dev.of_node,
                                "temperature-stability", &stability);
                if (err) {
                        dev_err(&client->dev,
                                  "'temperature-stability' property missing\n");
                        return err;
                }
                /* adjust register offsets for 7ppm devices */
                if (stability == 7)
                        data->div_offset = SI570_DIV_OFFSET_7PPM;
        }

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

        err = of_property_read_u32(client->dev.of_node, "factory-fout",
                        &factory_fout);
        if (err) {
                dev_err(&client->dev, "'factory-fout' property missing\n");
                return err;
        }

        skip_recall = of_property_read_bool(client->dev.of_node,
                                            "silabs,skip-recall");

        data->regmap = devm_regmap_init_i2c(client, &si570_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 = si570_get_defaults(data, factory_fout, skip_recall);
        if (err)
                return err;

        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;
        }

        /* Read the requested initial output frequency from device tree */
        if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
                                &initial_fout)) {
                err = clk_set_rate(data->hw.clk, initial_fout);
                if (err)
                        return err;
        }

        /* Display a message indicating that we've successfully registered */
        dev_info(&client->dev, "registered, current frequency %llu Hz\n",
                        data->frequency);

        return 0;
}

static const struct clk_si570_info clk_si570_info = {
        .max_freq = SI570_MAX_FREQ,
        .has_temperature_stability = true,
};

static const struct clk_si570_info clk_si590_info = {
        .max_freq = SI598_MAX_FREQ,
};

static const struct i2c_device_id si570_id[] = {
        { "si570", (kernel_ulong_t)&clk_si570_info },
        { "si571", (kernel_ulong_t)&clk_si570_info },
        { "si598", (kernel_ulong_t)&clk_si590_info },
        { "si599", (kernel_ulong_t)&clk_si590_info },
        { }
};
MODULE_DEVICE_TABLE(i2c, si570_id);

static const struct of_device_id clk_si570_of_match[] = {
        { .compatible = "silabs,si570", .data = &clk_si570_info },
        { .compatible = "silabs,si571", .data = &clk_si570_info },
        { .compatible = "silabs,si598", .data = &clk_si590_info },
        { .compatible = "silabs,si599", .data = &clk_si590_info },
        { }
};
MODULE_DEVICE_TABLE(of, clk_si570_of_match);

static struct i2c_driver si570_driver = {
        .driver = {
                .name = "si570",
                .of_match_table = clk_si570_of_match,
        },
        .probe          = si570_probe,
        .id_table       = si570_id,
};
module_i2c_driver(si570_driver);

MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com>");
MODULE_DESCRIPTION("Si570 driver");
MODULE_LICENSE("GPL");
Linux
