drivers/clk/clk-si521xx.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for Skyworks Si521xx PCIe clock generator driver
 *
 * The following series can be supported:
 *   - Si52144 - 4x DIFF
 *   - Si52146 - 6x DIFF
 *   - Si52147 - 9x DIFF
 * Currently tested:
 *   - Si52144
 *
 * Copyright (C) 2022 Marek Vasut <marex@denx.de>
 */

#include <linux/bitfield.h>
#include <linux/bitrev.h>
#include <linux/clk-provider.h>
#include <linux/i2c.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/regmap.h>

/* OE1 and OE2 register */
#define SI521XX_REG_OE(n)			(((n) & 0x1) + 1)
#define SI521XX_REG_ID				0x3
#define SI521XX_REG_ID_PROG			GENMASK(7, 4)
#define SI521XX_REG_ID_VENDOR			GENMASK(3, 0)
#define SI521XX_REG_BC				0x4
#define SI521XX_REG_DA				0x5
#define SI521XX_REG_DA_AMP_SEL			BIT(7)
#define SI521XX_REG_DA_AMP_MASK			GENMASK(6, 4)
#define SI521XX_REG_DA_AMP_MIN			300000
#define SI521XX_REG_DA_AMP_DEFAULT		800000
#define SI521XX_REG_DA_AMP_MAX			1000000
#define SI521XX_REG_DA_AMP_STEP			100000
#define SI521XX_REG_DA_AMP(UV)			\
	FIELD_PREP(SI521XX_REG_DA_AMP_MASK,	\
		   ((UV) - SI521XX_REG_DA_AMP_MIN) / SI521XX_REG_DA_AMP_STEP)
#define SI521XX_REG_DA_UNKNOWN			BIT(3)	/* Always set */

/* Count of populated OE bits in control register ref, 1 and 2 */
#define SI521XX_OE_MAP(cr1, cr2)	(((cr2) << 8) | (cr1))
#define SI521XX_OE_MAP_GET_OE(oe, map)	(((map) >> (((oe) - 1) * 8)) & 0xff)

#define SI521XX_DIFF_MULT	4
#define SI521XX_DIFF_DIV	1

/* Supported Skyworks Si521xx models. */
enum si521xx_model {
	SI52144 = 0x44,
	SI52146 = 0x46,
	SI52147 = 0x47,
};

struct si521xx;

struct si_clk {
	struct clk_hw		hw;
	struct si521xx		*si;
	u8			reg;
	u8			bit;
};

struct si521xx {
	struct i2c_client	*client;
	struct regmap		*regmap;
	struct si_clk		clk_dif[9];
	u16			chip_info;
	u8			pll_amplitude;
};

/*
 * Si521xx i2c regmap
 */
static const struct regmap_range si521xx_readable_ranges[] = {
	regmap_reg_range(SI521XX_REG_OE(0), SI521XX_REG_DA),
};

static const struct regmap_access_table si521xx_readable_table = {
	.yes_ranges = si521xx_readable_ranges,
	.n_yes_ranges = ARRAY_SIZE(si521xx_readable_ranges),
};

static const struct regmap_range si521xx_writeable_ranges[] = {
	regmap_reg_range(SI521XX_REG_OE(0), SI521XX_REG_OE(1)),
	regmap_reg_range(SI521XX_REG_BC, SI521XX_REG_DA),
};

static const struct regmap_access_table si521xx_writeable_table = {
	.yes_ranges = si521xx_writeable_ranges,
	.n_yes_ranges = ARRAY_SIZE(si521xx_writeable_ranges),
};

static int si521xx_regmap_i2c_write(void *context, unsigned int reg,
				    unsigned int val)
{
	struct i2c_client *i2c = context;
	const u8 data[3] = { reg, 1, val };
	const int count = ARRAY_SIZE(data);
	int ret;

	ret = i2c_master_send(i2c, data, count);
	if (ret == count)
		return 0;
	else if (ret < 0)
		return ret;
	else
		return -EIO;
}

static int si521xx_regmap_i2c_read(void *context, unsigned int reg,
				   unsigned int *val)
{
	struct i2c_client *i2c = context;
	struct i2c_msg xfer[2];
	u8 txdata = reg;
	u8 rxdata[2];
	int ret;

	xfer[0].addr = i2c->addr;
	xfer[0].flags = 0;
	xfer[0].len = 1;
	xfer[0].buf = (void *)&txdata;

	xfer[1].addr = i2c->addr;
	xfer[1].flags = I2C_M_RD;
	xfer[1].len = 2;
	xfer[1].buf = (void *)rxdata;

	ret = i2c_transfer(i2c->adapter, xfer, 2);
	if (ret < 0)
		return ret;
	if (ret != 2)
		return -EIO;

	/*
	 * Byte 0 is transfer length, which is always 1 due
	 * to BCP register programming to 1 in si521xx_probe(),
	 * ignore it and use data from Byte 1.
	 */
	*val = rxdata[1];
	return 0;
}

static const struct regmap_config si521xx_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.cache_type = REGCACHE_NONE,
	.max_register = SI521XX_REG_DA,
	.rd_table = &si521xx_readable_table,
	.wr_table = &si521xx_writeable_table,
	.reg_write = si521xx_regmap_i2c_write,
	.reg_read = si521xx_regmap_i2c_read,
};

static unsigned long si521xx_diff_recalc_rate(struct clk_hw *hw,
					      unsigned long parent_rate)
{
	unsigned long long rate;

	rate = (unsigned long long)parent_rate * SI521XX_DIFF_MULT;
	do_div(rate, SI521XX_DIFF_DIV);
	return (unsigned long)rate;
}

static long si521xx_diff_round_rate(struct clk_hw *hw, unsigned long rate,
				    unsigned long *prate)
{
	unsigned long best_parent;

	best_parent = (rate / SI521XX_DIFF_MULT) * SI521XX_DIFF_DIV;
	*prate = clk_hw_round_rate(clk_hw_get_parent(hw), best_parent);

	return (*prate / SI521XX_DIFF_DIV) * SI521XX_DIFF_MULT;
}

static int si521xx_diff_set_rate(struct clk_hw *hw, unsigned long rate,
				 unsigned long parent_rate)
{
	/*
	 * We must report success but we can do so unconditionally because
	 * si521xx_diff_round_rate returns values that ensure this call is a
	 * nop.
	 */

	return 0;
}

#define to_si521xx_clk(_hw) container_of(_hw, struct si_clk, hw)

static int si521xx_diff_prepare(struct clk_hw *hw)
{
	struct si_clk *si_clk = to_si521xx_clk(hw);
	struct si521xx *si = si_clk->si;

	regmap_set_bits(si->regmap, SI521XX_REG_OE(si_clk->reg), si_clk->bit);

	return 0;
}

static void si521xx_diff_unprepare(struct clk_hw *hw)
{
	struct si_clk *si_clk = to_si521xx_clk(hw);
	struct si521xx *si = si_clk->si;

	regmap_clear_bits(si->regmap, SI521XX_REG_OE(si_clk->reg), si_clk->bit);
}

static const struct clk_ops si521xx_diff_clk_ops = {
	.round_rate	= si521xx_diff_round_rate,
	.set_rate	= si521xx_diff_set_rate,
	.recalc_rate	= si521xx_diff_recalc_rate,
	.prepare	= si521xx_diff_prepare,
	.unprepare	= si521xx_diff_unprepare,
};

static int si521xx_get_common_config(struct si521xx *si)
{
	struct i2c_client *client = si->client;
	struct device_node *np = client->dev.of_node;
	unsigned int amp;
	int ret;

	/* Set defaults */
	si->pll_amplitude = SI521XX_REG_DA_AMP(SI521XX_REG_DA_AMP_DEFAULT);

	/* Output clock amplitude */
	ret = of_property_read_u32(np, "skyworks,out-amplitude-microvolt",
				   &amp);
	if (!ret) {
		if (amp < SI521XX_REG_DA_AMP_MIN || amp > SI521XX_REG_DA_AMP_MAX ||
		    amp % SI521XX_REG_DA_AMP_STEP) {
			return dev_err_probe(&client->dev, -EINVAL,
					     "Invalid skyworks,out-amplitude-microvolt value\n");
		}
		si->pll_amplitude = SI521XX_REG_DA_AMP(amp);
	}

	return 0;
}

static void si521xx_update_config(struct si521xx *si)
{
	/* If amplitude is non-default, update it. */
	if (si->pll_amplitude == SI521XX_REG_DA_AMP(SI521XX_REG_DA_AMP_DEFAULT))
		return;

	regmap_update_bits(si->regmap, SI521XX_REG_DA,
			   SI521XX_REG_DA_AMP_MASK, si->pll_amplitude);
}

static void si521xx_diff_idx_to_reg_bit(const u16 chip_info, const int idx,
					struct si_clk *clk)
{
	unsigned long mask;
	int oe, b, ctr = 0;

	for (oe = 1; oe <= 2; oe++) {
		mask = bitrev8(SI521XX_OE_MAP_GET_OE(oe, chip_info));
		for_each_set_bit(b, &mask, 8) {
			if (ctr++ != idx)
				continue;
			clk->reg = SI521XX_REG_OE(oe);
			clk->bit = 7 - b;
			return;
		}
	}
}

static struct clk_hw *
si521xx_of_clk_get(struct of_phandle_args *clkspec, void *data)
{
	struct si521xx *si = data;
	unsigned int idx = clkspec->args[0];

	return &si->clk_dif[idx].hw;
}

static int si521xx_probe(struct i2c_client *client)
{
	const u16 chip_info = (u16)(uintptr_t)device_get_match_data(&client->dev);
	const struct clk_parent_data clk_parent_data = { .index = 0 };
	struct si521xx *si;
	unsigned char name[6] = "DIFF0";
	struct clk_init_data init = {};
	int i, ret;

	if (!chip_info)
		return -EINVAL;

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

	i2c_set_clientdata(client, si);
	si->client = client;

	/* Fetch common configuration from DT (if specified) */
	ret = si521xx_get_common_config(si);
	if (ret)
		return ret;

	si->regmap = devm_regmap_init(&client->dev, NULL, client,
				      &si521xx_regmap_config);
	if (IS_ERR(si->regmap))
		return dev_err_probe(&client->dev, PTR_ERR(si->regmap),
				     "Failed to allocate register map\n");

	/* Always read back 1 Byte via I2C */
	ret = regmap_write(si->regmap, SI521XX_REG_BC, 1);
	if (ret < 0)
		return ret;

	/* Register clock */
	for (i = 0; i < hweight16(chip_info); i++) {
		memset(&init, 0, sizeof(init));
		snprintf(name, 6, "DIFF%d", i);
		init.name = name;
		init.ops = &si521xx_diff_clk_ops;
		init.parent_data = &clk_parent_data;
		init.num_parents = 1;
		init.flags = CLK_SET_RATE_PARENT;

		si->clk_dif[i].hw.init = &init;
		si->clk_dif[i].si = si;

		si521xx_diff_idx_to_reg_bit(chip_info, i, &si->clk_dif[i]);

		ret = devm_clk_hw_register(&client->dev, &si->clk_dif[i].hw);
		if (ret)
			return ret;
	}

	ret = devm_of_clk_add_hw_provider(&client->dev, si521xx_of_clk_get, si);
	if (!ret)
		si521xx_update_config(si);

	return ret;
}

static int __maybe_unused si521xx_suspend(struct device *dev)
{
	struct si521xx *si = dev_get_drvdata(dev);

	regcache_cache_only(si->regmap, true);
	regcache_mark_dirty(si->regmap);

	return 0;
}

static int __maybe_unused si521xx_resume(struct device *dev)
{
	struct si521xx *si = dev_get_drvdata(dev);
	int ret;

	regcache_cache_only(si->regmap, false);
	ret = regcache_sync(si->regmap);
	if (ret)
		dev_err(dev, "Failed to restore register map: %d\n", ret);
	return ret;
}

static const struct i2c_device_id si521xx_id[] = {
	{ "si52144", .driver_data = SI521XX_OE_MAP(0x5, 0xc0) },
	{ "si52146", .driver_data = SI521XX_OE_MAP(0x15, 0xe0) },
	{ "si52147", .driver_data = SI521XX_OE_MAP(0x17, 0xf8) },
	{ }
};
MODULE_DEVICE_TABLE(i2c, si521xx_id);

static const struct of_device_id clk_si521xx_of_match[] = {
	{ .compatible = "skyworks,si52144", .data = (void *)SI521XX_OE_MAP(0x5, 0xc0) },
	{ .compatible = "skyworks,si52146", .data = (void *)SI521XX_OE_MAP(0x15, 0xe0) },
	{ .compatible = "skyworks,si52147", .data = (void *)SI521XX_OE_MAP(0x15, 0xf8) },
	{ }
};
MODULE_DEVICE_TABLE(of, clk_si521xx_of_match);

static SIMPLE_DEV_PM_OPS(si521xx_pm_ops, si521xx_suspend, si521xx_resume);

static struct i2c_driver si521xx_driver = {
	.driver = {
		.name = "clk-si521xx",
		.pm	= &si521xx_pm_ops,
		.of_match_table = clk_si521xx_of_match,
	},
	.probe		= si521xx_probe,
	.id_table	= si521xx_id,
};
module_i2c_driver(si521xx_driver);

MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
MODULE_DESCRIPTION("Skyworks Si521xx PCIe clock generator driver");
MODULE_LICENSE("GPL");