/*
 * Copyright (C) 2016 Maxime Ripard
 * Maxime Ripard <maxime.ripard@free-electrons.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 */

#include <linux/clk-provider.h>
#include <linux/rational.h>

#include "ccu_gate.h"
#include "ccu_nkm.h"

struct _ccu_nkm {
	unsigned long	n, max_n;
	unsigned long	k, max_k;
	unsigned long	m, max_m;
};

static void ccu_nkm_find_best(unsigned long parent, unsigned long rate,
			      struct _ccu_nkm *nkm)
{
	unsigned long best_rate = 0;
	unsigned long best_n = 0, best_k = 0, best_m = 0;
	unsigned long _n, _k, _m;

	for (_k = 1; _k <= nkm->max_k; _k++) {
		unsigned long tmp_rate;

		rational_best_approximation(rate / _k, parent,
					    nkm->max_n, nkm->max_m, &_n, &_m);

		tmp_rate = parent * _n * _k / _m;

		if (tmp_rate > rate)
			continue;

		if ((rate - tmp_rate) < (rate - best_rate)) {
			best_rate = tmp_rate;
			best_n = _n;
			best_k = _k;
			best_m = _m;
		}
	}

	nkm->n = best_n;
	nkm->k = best_k;
	nkm->m = best_m;
}

static void ccu_nkm_disable(struct clk_hw *hw)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);

	return ccu_gate_helper_disable(&nkm->common, nkm->enable);
}

static int ccu_nkm_enable(struct clk_hw *hw)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);

	return ccu_gate_helper_enable(&nkm->common, nkm->enable);
}

static int ccu_nkm_is_enabled(struct clk_hw *hw)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);

	return ccu_gate_helper_is_enabled(&nkm->common, nkm->enable);
}

static unsigned long ccu_nkm_recalc_rate(struct clk_hw *hw,
					unsigned long parent_rate)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);
	unsigned long n, m, k;
	u32 reg;

	reg = readl(nkm->common.base + nkm->common.reg);

	n = reg >> nkm->n.shift;
	n &= (1 << nkm->n.width) - 1;

	k = reg >> nkm->k.shift;
	k &= (1 << nkm->k.width) - 1;

	m = reg >> nkm->m.shift;
	m &= (1 << nkm->m.width) - 1;

	return parent_rate * (n + 1) * (k + 1) / (m + 1);
}

static long ccu_nkm_round_rate(struct clk_hw *hw, unsigned long rate,
			      unsigned long *parent_rate)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);
	struct _ccu_nkm _nkm;

	_nkm.max_n = 1 << nkm->n.width;
	_nkm.max_k = 1 << nkm->k.width;
	_nkm.max_m = 1 << nkm->m.width;

	ccu_nkm_find_best(*parent_rate, rate, &_nkm);

	return *parent_rate * _nkm.n * _nkm.k / _nkm.m;
}

static int ccu_nkm_set_rate(struct clk_hw *hw, unsigned long rate,
			   unsigned long parent_rate)
{
	struct ccu_nkm *nkm = hw_to_ccu_nkm(hw);
	struct _ccu_nkm _nkm;
	unsigned long flags;
	u32 reg;

	_nkm.max_n = 1 << nkm->n.width;
	_nkm.max_k = 1 << nkm->k.width;
	_nkm.max_m = 1 << nkm->m.width;

	ccu_nkm_find_best(parent_rate, rate, &_nkm);

	spin_lock_irqsave(nkm->common.lock, flags);

	reg = readl(nkm->common.base + nkm->common.reg);
	reg &= ~GENMASK(nkm->n.width + nkm->n.shift - 1, nkm->n.shift);
	reg &= ~GENMASK(nkm->k.width + nkm->k.shift - 1, nkm->k.shift);
	reg &= ~GENMASK(nkm->m.width + nkm->m.shift - 1, nkm->m.shift);

	reg |= (_nkm.n - 1) << nkm->n.shift;
	reg |= (_nkm.k - 1) << nkm->k.shift;
	reg |= (_nkm.m - 1) << nkm->m.shift;

	writel(reg, nkm->common.base + nkm->common.reg);

	spin_unlock_irqrestore(nkm->common.lock, flags);

	ccu_helper_wait_for_lock(&nkm->common, nkm->lock);

	return 0;
}

const struct clk_ops ccu_nkm_ops = {
	.disable	= ccu_nkm_disable,
	.enable		= ccu_nkm_enable,
	.is_enabled	= ccu_nkm_is_enabled,

	.recalc_rate	= ccu_nkm_recalc_rate,
	.round_rate	= ccu_nkm_round_rate,
	.set_rate	= ccu_nkm_set_rate,
};