linux-next/drivers/clk/meson/clk-pll.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2015 Endless Mobile, Inc.
 * Author: Carlo Caione <carlo@endlessm.com>
 *
 * Copyright (c) 2018 Baylibre, SAS.
 * Author: Jerome Brunet <jbrunet@baylibre.com>
 */

/*
 * In the most basic form, a Meson PLL is composed as follows:
 *
 *                     PLL
 *        +--------------------------------+
 *        |                                |
 *        |             +--+               |
 *  in >>-----[ /N ]--->|  |      +-----+  |
 *        |             |  |------| DCO |---->> out
 *        |  +--------->|  |      +--v--+  |
 *        |  |          +--+         |     |
 *        |  |                       |     |
 *        |  +--[ *(M + (F/Fmax) ]<--+     |
 *        |                                |
 *        +--------------------------------+
 *
 * out = in * (m + frac / frac_max) / n
 */

#include <linux/clk-provider.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/slab.h>
#include <linux/string.h>

#include "clkc.h"

static inline struct meson_clk_pll_data *
meson_clk_pll_data(struct clk_regmap *clk)
{
	return (struct meson_clk_pll_data *)clk->data;
}

static unsigned long __pll_params_to_rate(unsigned long parent_rate,
					  const struct pll_params_table *pllt,
					  u16 frac,
					  struct meson_clk_pll_data *pll)
{
	u64 rate = (u64)parent_rate * pllt->m;

	if (frac && MESON_PARM_APPLICABLE(&pll->frac)) {
		u64 frac_rate = (u64)parent_rate * frac;

		rate += DIV_ROUND_UP_ULL(frac_rate,
					 (1 << pll->frac.width));
	}

	return DIV_ROUND_UP_ULL(rate, pllt->n);
}

static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
						unsigned long parent_rate)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
	struct pll_params_table pllt;
	u16 frac;

	pllt.n = meson_parm_read(clk->map, &pll->n);
	pllt.m = meson_parm_read(clk->map, &pll->m);

	frac = MESON_PARM_APPLICABLE(&pll->frac) ?
		meson_parm_read(clk->map, &pll->frac) :
		0;

	return __pll_params_to_rate(parent_rate, &pllt, frac, pll);
}

static u16 __pll_params_with_frac(unsigned long rate,
				  unsigned long parent_rate,
				  const struct pll_params_table *pllt,
				  struct meson_clk_pll_data *pll)
{
	u16 frac_max = (1 << pll->frac.width);
	u64 val = (u64)rate * pllt->n;

	if (pll->flags & CLK_MESON_PLL_ROUND_CLOSEST)
		val = DIV_ROUND_CLOSEST_ULL(val * frac_max, parent_rate);
	else
		val = div_u64(val * frac_max, parent_rate);

	val -= pllt->m * frac_max;

	return min((u16)val, (u16)(frac_max - 1));
}

static bool meson_clk_pll_is_better(unsigned long rate,
				    unsigned long best,
				    unsigned long now,
				    struct meson_clk_pll_data *pll)
{
	if (!(pll->flags & CLK_MESON_PLL_ROUND_CLOSEST) ||
	    MESON_PARM_APPLICABLE(&pll->frac)) {
		/* Round down */
		if (now < rate && best < now)
			return true;
	} else {
		/* Round Closest */
		if (abs(now - rate) < abs(best - rate))
			return true;
	}

	return false;
}

static const struct pll_params_table *
meson_clk_get_pll_settings(unsigned long rate,
			   unsigned long parent_rate,
			   struct meson_clk_pll_data *pll)
{
	const struct pll_params_table *table = pll->table;
	unsigned long best = 0, now = 0;
	unsigned int i, best_i = 0;

	if (!table)
		return NULL;

	for (i = 0; table[i].n; i++) {
		now = __pll_params_to_rate(parent_rate, &table[i], 0, pll);

		/* If we get an exact match, don't bother any further */
		if (now == rate) {
			return &table[i];
		} else if (meson_clk_pll_is_better(rate, best, now, pll)) {
			best = now;
			best_i = i;
		}
	}

	return (struct pll_params_table *)&table[best_i];
}

static long meson_clk_pll_round_rate(struct clk_hw *hw, unsigned long rate,
				     unsigned long *parent_rate)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
	const struct pll_params_table *pllt =
		meson_clk_get_pll_settings(rate, *parent_rate, pll);
	unsigned long round;
	u16 frac;

	if (!pllt)
		return meson_clk_pll_recalc_rate(hw, *parent_rate);

	round = __pll_params_to_rate(*parent_rate, pllt, 0, pll);

	if (!MESON_PARM_APPLICABLE(&pll->frac) || rate == round)
		return round;

	/*
	 * The rate provided by the setting is not an exact match, let's
	 * try to improve the result using the fractional parameter
	 */
	frac = __pll_params_with_frac(rate, *parent_rate, pllt, pll);

	return __pll_params_to_rate(*parent_rate, pllt, frac, pll);
}

static int meson_clk_pll_wait_lock(struct clk_hw *hw)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
	int delay = 24000000;

	do {
		/* Is the clock locked now ? */
		if (meson_parm_read(clk->map, &pll->l))
			return 0;

		delay--;
	} while (delay > 0);

	return -ETIMEDOUT;
}

static void meson_clk_pll_init(struct clk_hw *hw)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);

	if (pll->init_count) {
		meson_parm_write(clk->map, &pll->rst, 1);
		regmap_multi_reg_write(clk->map, pll->init_regs,
				       pll->init_count);
		meson_parm_write(clk->map, &pll->rst, 0);
	}
}

static int meson_clk_pll_enable(struct clk_hw *hw)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);

	/* Make sure the pll is in reset */
	meson_parm_write(clk->map, &pll->rst, 1);

	/* Enable the pll */
	meson_parm_write(clk->map, &pll->en, 1);

	/* Take the pll out reset */
	meson_parm_write(clk->map, &pll->rst, 0);

	if (meson_clk_pll_wait_lock(hw))
		return -EIO;

	return 0;
}

static void meson_clk_pll_disable(struct clk_hw *hw)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);

	/* Put the pll is in reset */
	meson_parm_write(clk->map, &pll->rst, 1);

	/* Disable the pll */
	meson_parm_write(clk->map, &pll->en, 0);
}

static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
				  unsigned long parent_rate)
{
	struct clk_regmap *clk = to_clk_regmap(hw);
	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
	const struct pll_params_table *pllt;
	unsigned int enabled;
	unsigned long old_rate;
	u16 frac = 0;

	if (parent_rate == 0 || rate == 0)
		return -EINVAL;

	old_rate = rate;

	pllt = meson_clk_get_pll_settings(rate, parent_rate, pll);
	if (!pllt)
		return -EINVAL;

	enabled = meson_parm_read(clk->map, &pll->en);
	if (enabled)
		meson_clk_pll_disable(hw);

	meson_parm_write(clk->map, &pll->n, pllt->n);
	meson_parm_write(clk->map, &pll->m, pllt->m);


	if (MESON_PARM_APPLICABLE(&pll->frac)) {
		frac = __pll_params_with_frac(rate, parent_rate, pllt, pll);
		meson_parm_write(clk->map, &pll->frac, frac);
	}

	/* If the pll is stopped, bail out now */
	if (!enabled)
		return 0;

	if (meson_clk_pll_enable(hw)) {
		pr_warn("%s: pll did not lock, trying to restore old rate %lu\n",
			__func__, old_rate);
		/*
		 * FIXME: Do we really need/want this HACK ?
		 * It looks unsafe. what happens if the clock gets into a
		 * broken state and we can't lock back on the old_rate ? Looks
		 * like an infinite recursion is possible
		 */
		meson_clk_pll_set_rate(hw, old_rate, parent_rate);
	}

	return 0;
}

const struct clk_ops meson_clk_pll_ops = {
	.init		= meson_clk_pll_init,
	.recalc_rate	= meson_clk_pll_recalc_rate,
	.round_rate	= meson_clk_pll_round_rate,
	.set_rate	= meson_clk_pll_set_rate,
	.enable		= meson_clk_pll_enable,
	.disable	= meson_clk_pll_disable
};

const struct clk_ops meson_clk_pll_ro_ops = {
	.recalc_rate	= meson_clk_pll_recalc_rate,
};