/*
 * Copyright (C) 2014 Broadcom Corporation
 *
 * 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 version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk-provider.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/clkdev.h>
#include <linux/of_address.h>

#define IPROC_CLK_MAX_FREQ_POLICY                    0x3
#define IPROC_CLK_POLICY_FREQ_OFFSET                 0x008
#define IPROC_CLK_POLICY_FREQ_POLICY_FREQ_SHIFT      8
#define IPROC_CLK_POLICY_FREQ_POLICY_FREQ_MASK       0x7

#define IPROC_CLK_PLLARMA_OFFSET                     0xc00
#define IPROC_CLK_PLLARMA_LOCK_SHIFT                 28
#define IPROC_CLK_PLLARMA_PDIV_SHIFT                 24
#define IPROC_CLK_PLLARMA_PDIV_MASK                  0xf
#define IPROC_CLK_PLLARMA_NDIV_INT_SHIFT             8
#define IPROC_CLK_PLLARMA_NDIV_INT_MASK              0x3ff

#define IPROC_CLK_PLLARMB_OFFSET                     0xc04
#define IPROC_CLK_PLLARMB_NDIV_FRAC_MASK             0xfffff

#define IPROC_CLK_PLLARMC_OFFSET                     0xc08
#define IPROC_CLK_PLLARMC_BYPCLK_EN_SHIFT            8
#define IPROC_CLK_PLLARMC_MDIV_MASK                  0xff

#define IPROC_CLK_PLLARMCTL5_OFFSET                  0xc20
#define IPROC_CLK_PLLARMCTL5_H_MDIV_MASK             0xff

#define IPROC_CLK_PLLARM_OFFSET_OFFSET               0xc24
#define IPROC_CLK_PLLARM_SW_CTL_SHIFT                29
#define IPROC_CLK_PLLARM_NDIV_INT_OFFSET_SHIFT       20
#define IPROC_CLK_PLLARM_NDIV_INT_OFFSET_MASK        0xff
#define IPROC_CLK_PLLARM_NDIV_FRAC_OFFSET_MASK       0xfffff

#define IPROC_CLK_ARM_DIV_OFFSET                     0xe00
#define IPROC_CLK_ARM_DIV_PLL_SELECT_OVERRIDE_SHIFT  4
#define IPROC_CLK_ARM_DIV_ARM_PLL_SELECT_MASK        0xf

#define IPROC_CLK_POLICY_DBG_OFFSET                  0xec0
#define IPROC_CLK_POLICY_DBG_ACT_FREQ_SHIFT          12
#define IPROC_CLK_POLICY_DBG_ACT_FREQ_MASK           0x7

enum iproc_arm_pll_fid {
	ARM_PLL_FID_CRYSTAL_CLK   = 0,
	ARM_PLL_FID_SYS_CLK       = 2,
	ARM_PLL_FID_CH0_SLOW_CLK  = 6,
	ARM_PLL_FID_CH1_FAST_CLK  = 7
};

struct iproc_arm_pll {
	struct clk_hw hw;
	void __iomem *base;
	unsigned long rate;
};

#define to_iproc_arm_pll(hw) container_of(hw, struct iproc_arm_pll, hw)

static unsigned int __get_fid(struct iproc_arm_pll *pll)
{
	u32 val;
	unsigned int policy, fid, active_fid;

	val = readl(pll->base + IPROC_CLK_ARM_DIV_OFFSET);
	if (val & (1 << IPROC_CLK_ARM_DIV_PLL_SELECT_OVERRIDE_SHIFT))
		policy = val & IPROC_CLK_ARM_DIV_ARM_PLL_SELECT_MASK;
	else
		policy = 0;

	/* something is seriously wrong */
	BUG_ON(policy > IPROC_CLK_MAX_FREQ_POLICY);

	val = readl(pll->base + IPROC_CLK_POLICY_FREQ_OFFSET);
	fid = (val >> (IPROC_CLK_POLICY_FREQ_POLICY_FREQ_SHIFT * policy)) &
		IPROC_CLK_POLICY_FREQ_POLICY_FREQ_MASK;

	val = readl(pll->base + IPROC_CLK_POLICY_DBG_OFFSET);
	active_fid = IPROC_CLK_POLICY_DBG_ACT_FREQ_MASK &
		(val >> IPROC_CLK_POLICY_DBG_ACT_FREQ_SHIFT);
	if (fid != active_fid) {
		pr_debug("%s: fid override %u->%u\n", __func__,	fid,
				active_fid);
		fid = active_fid;
	}

	pr_debug("%s: active fid: %u\n", __func__, fid);

	return fid;
}

/*
 * Determine the mdiv (post divider) based on the frequency ID being used.
 * There are 4 sources that can be used to derive the output clock rate:
 *    - 25 MHz Crystal
 *    - System clock
 *    - PLL channel 0 (slow clock)
 *    - PLL channel 1 (fast clock)
 */
static int __get_mdiv(struct iproc_arm_pll *pll)
{
	unsigned int fid;
	int mdiv;
	u32 val;

	fid = __get_fid(pll);

	switch (fid) {
	case ARM_PLL_FID_CRYSTAL_CLK:
	case ARM_PLL_FID_SYS_CLK:
		mdiv = 1;
		break;

	case ARM_PLL_FID_CH0_SLOW_CLK:
		val = readl(pll->base + IPROC_CLK_PLLARMC_OFFSET);
		mdiv = val & IPROC_CLK_PLLARMC_MDIV_MASK;
		if (mdiv == 0)
			mdiv = 256;
		break;

	case ARM_PLL_FID_CH1_FAST_CLK:
		val = readl(pll->base +	IPROC_CLK_PLLARMCTL5_OFFSET);
		mdiv = val & IPROC_CLK_PLLARMCTL5_H_MDIV_MASK;
		if (mdiv == 0)
			mdiv = 256;
		break;

	default:
		mdiv = -EFAULT;
	}

	return mdiv;
}

static unsigned int __get_ndiv(struct iproc_arm_pll *pll)
{
	u32 val;
	unsigned int ndiv_int, ndiv_frac, ndiv;

	val = readl(pll->base + IPROC_CLK_PLLARM_OFFSET_OFFSET);
	if (val & (1 << IPROC_CLK_PLLARM_SW_CTL_SHIFT)) {
		/*
		 * offset mode is active. Read the ndiv from the PLLARM OFFSET
		 * register
		 */
		ndiv_int = (val >> IPROC_CLK_PLLARM_NDIV_INT_OFFSET_SHIFT) &
			IPROC_CLK_PLLARM_NDIV_INT_OFFSET_MASK;
		if (ndiv_int == 0)
			ndiv_int = 256;

		ndiv_frac = val & IPROC_CLK_PLLARM_NDIV_FRAC_OFFSET_MASK;
	} else {
		/* offset mode not active */
		val = readl(pll->base + IPROC_CLK_PLLARMA_OFFSET);
		ndiv_int = (val >> IPROC_CLK_PLLARMA_NDIV_INT_SHIFT) &
			IPROC_CLK_PLLARMA_NDIV_INT_MASK;
		if (ndiv_int == 0)
			ndiv_int = 1024;

		val = readl(pll->base + IPROC_CLK_PLLARMB_OFFSET);
		ndiv_frac = val & IPROC_CLK_PLLARMB_NDIV_FRAC_MASK;
	}

	ndiv = (ndiv_int << 20) | ndiv_frac;

	return ndiv;
}

/*
 * The output frequency of the ARM PLL is calculated based on the ARM PLL
 * divider values:
 *   pdiv = ARM PLL pre-divider
 *   ndiv = ARM PLL multiplier
 *   mdiv = ARM PLL post divider
 *
 * The frequency is calculated by:
 *   ((ndiv * parent clock rate) / pdiv) / mdiv
 */
static unsigned long iproc_arm_pll_recalc_rate(struct clk_hw *hw,
		unsigned long parent_rate)
{
	struct iproc_arm_pll *pll = to_iproc_arm_pll(hw);
	u32 val;
	int mdiv;
	u64 ndiv;
	unsigned int pdiv;

	/* in bypass mode, use parent rate */
	val = readl(pll->base + IPROC_CLK_PLLARMC_OFFSET);
	if (val & (1 << IPROC_CLK_PLLARMC_BYPCLK_EN_SHIFT)) {
		pll->rate = parent_rate;
		return pll->rate;
	}

	/* PLL needs to be locked */
	val = readl(pll->base + IPROC_CLK_PLLARMA_OFFSET);
	if (!(val & (1 << IPROC_CLK_PLLARMA_LOCK_SHIFT))) {
		pll->rate = 0;
		return 0;
	}

	pdiv = (val >> IPROC_CLK_PLLARMA_PDIV_SHIFT) &
		IPROC_CLK_PLLARMA_PDIV_MASK;
	if (pdiv == 0)
		pdiv = 16;

	ndiv = __get_ndiv(pll);
	mdiv = __get_mdiv(pll);
	if (mdiv <= 0) {
		pll->rate = 0;
		return 0;
	}
	pll->rate = (ndiv * parent_rate) >> 20;
	pll->rate = (pll->rate / pdiv) / mdiv;

	pr_debug("%s: ARM PLL rate: %lu. parent rate: %lu\n", __func__,
		 pll->rate, parent_rate);
	pr_debug("%s: ndiv_int: %u, pdiv: %u, mdiv: %d\n", __func__,
		 (unsigned int)(ndiv >> 20), pdiv, mdiv);

	return pll->rate;
}

static const struct clk_ops iproc_arm_pll_ops = {
	.recalc_rate = iproc_arm_pll_recalc_rate,
};

void __init iproc_armpll_setup(struct device_node *node)
{
	int ret;
	struct clk *clk;
	struct iproc_arm_pll *pll;
	struct clk_init_data init;
	const char *parent_name;

	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
	if (WARN_ON(!pll))
		return;

	pll->base = of_iomap(node, 0);
	if (WARN_ON(!pll->base))
		goto err_free_pll;

	init.name = node->name;
	init.ops = &iproc_arm_pll_ops;
	init.flags = 0;
	parent_name = of_clk_get_parent_name(node, 0);
	init.parent_names = (parent_name ? &parent_name : NULL);
	init.num_parents = (parent_name ? 1 : 0);
	pll->hw.init = &init;

	clk = clk_register(NULL, &pll->hw);
	if (WARN_ON(IS_ERR(clk)))
		goto err_iounmap;

	ret = of_clk_add_provider(node, of_clk_src_simple_get, clk);
	if (WARN_ON(ret))
		goto err_clk_unregister;

	return;

err_clk_unregister:
	clk_unregister(clk);
err_iounmap:
	iounmap(pll->base);
err_free_pll:
	kfree(pll);
}