/*
 * OMAP2/3/4 DPLL clock functions
 *
 * Copyright (C) 2005-2008 Texas Instruments, Inc.
 * Copyright (C) 2004-2010 Nokia Corporation
 *
 * Contacts:
 * Richard Woodruff <r-woodruff2@ti.com>
 * Paul Walmsley
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#undef DEBUG

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/io.h>
#include <linux/clk/ti.h>

#include <asm/div64.h>

#include "clock.h"

/* DPLL rate rounding: minimum DPLL multiplier, divider values */
#define DPLL_MIN_MULTIPLIER             2
#define DPLL_MIN_DIVIDER                1

/* Possible error results from _dpll_test_mult */
#define DPLL_MULT_UNDERFLOW             -1

/*
 * Scale factor to mitigate roundoff errors in DPLL rate rounding.
 * The higher the scale factor, the greater the risk of arithmetic overflow,
 * but the closer the rounded rate to the target rate.  DPLL_SCALE_FACTOR
 * must be a power of DPLL_SCALE_BASE.
 */
#define DPLL_SCALE_FACTOR               64
#define DPLL_SCALE_BASE                 2
#define DPLL_ROUNDING_VAL               ((DPLL_SCALE_BASE / 2) * \
                                         (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE))

/*
 * DPLL valid Fint frequency range for OMAP36xx and OMAP4xxx.
 * From device data manual section 4.3 "DPLL and DLL Specifications".
 */
#define OMAP3PLUS_DPLL_FINT_JTYPE_MIN   500000
#define OMAP3PLUS_DPLL_FINT_JTYPE_MAX   2500000

/* _dpll_test_fint() return codes */
#define DPLL_FINT_UNDERFLOW             -1
#define DPLL_FINT_INVALID               -2

/* Private functions */

/*
 * _dpll_test_fint - test whether an Fint value is valid for the DPLL
 * @clk: DPLL struct clk to test
 * @n: divider value (N) to test
 *
 * Tests whether a particular divider @n will result in a valid DPLL
 * internal clock frequency Fint. See the 34xx TRM 4.7.6.2 "DPLL Jitter
 * Correction".  Returns 0 if OK, -1 if the enclosing loop can terminate
 * (assuming that it is counting N upwards), or -2 if the enclosing loop
 * should skip to the next iteration (again assuming N is increasing).
 */
static int _dpll_test_fint(struct clk_hw_omap *clk, unsigned int n)
{
        struct dpll_data *dd;
        long fint, fint_min, fint_max;
        int ret = 0;

        dd = clk->dpll_data;

        /* DPLL divider must result in a valid jitter correction val */
        fint = clk_hw_get_rate(clk_hw_get_parent(&clk->hw)) / n;

        if (dd->flags & DPLL_J_TYPE) {
                fint_min = OMAP3PLUS_DPLL_FINT_JTYPE_MIN;
                fint_max = OMAP3PLUS_DPLL_FINT_JTYPE_MAX;
        } else {
                fint_min = ti_clk_get_features()->fint_min;
                fint_max = ti_clk_get_features()->fint_max;
        }

        if (!fint_min || !fint_max) {
                WARN(1, "No fint limits available!\n");
                return DPLL_FINT_INVALID;
        }

        if (fint < ti_clk_get_features()->fint_min) {
                pr_debug("rejecting n=%d due to Fint failure, lowering max_divider\n",
                         n);
                dd->max_divider = n;
                ret = DPLL_FINT_UNDERFLOW;
        } else if (fint > ti_clk_get_features()->fint_max) {
                pr_debug("rejecting n=%d due to Fint failure, boosting min_divider\n",
                         n);
                dd->min_divider = n;
                ret = DPLL_FINT_INVALID;
        } else if (fint > ti_clk_get_features()->fint_band1_max &&
                   fint < ti_clk_get_features()->fint_band2_min) {
                pr_debug("rejecting n=%d due to Fint failure\n", n);
                ret = DPLL_FINT_INVALID;
        }

        return ret;
}

static unsigned long _dpll_compute_new_rate(unsigned long parent_rate,
                                            unsigned int m, unsigned int n)
{
        unsigned long long num;

        num = (unsigned long long)parent_rate * m;
        do_div(num, n);
        return num;
}

/*
 * _dpll_test_mult - test a DPLL multiplier value
 * @m: pointer to the DPLL m (multiplier) value under test
 * @n: current DPLL n (divider) value under test
 * @new_rate: pointer to storage for the resulting rounded rate
 * @target_rate: the desired DPLL rate
 * @parent_rate: the DPLL's parent clock rate
 *
 * This code tests a DPLL multiplier value, ensuring that the
 * resulting rate will not be higher than the target_rate, and that
 * the multiplier value itself is valid for the DPLL.  Initially, the
 * integer pointed to by the m argument should be prescaled by
 * multiplying by DPLL_SCALE_FACTOR.  The code will replace this with
 * a non-scaled m upon return.  This non-scaled m will result in a
 * new_rate as close as possible to target_rate (but not greater than
 * target_rate) given the current (parent_rate, n, prescaled m)
 * triple. Returns DPLL_MULT_UNDERFLOW in the event that the
 * non-scaled m attempted to underflow, which can allow the calling
 * function to bail out early; or 0 upon success.
 */
static int _dpll_test_mult(int *m, int n, unsigned long *new_rate,
                           unsigned long target_rate,
                           unsigned long parent_rate)
{
        int r = 0, carry = 0;

        /* Unscale m and round if necessary */
        if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL)
                carry = 1;
        *m = (*m / DPLL_SCALE_FACTOR) + carry;

        /*
         * The new rate must be <= the target rate to avoid programming
         * a rate that is impossible for the hardware to handle
         */
        *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
        if (*new_rate > target_rate) {
                (*m)--;
                *new_rate = 0;
        }

        /* Guard against m underflow */
        if (*m < DPLL_MIN_MULTIPLIER) {
                *m = DPLL_MIN_MULTIPLIER;
                *new_rate = 0;
                r = DPLL_MULT_UNDERFLOW;
        }

        if (*new_rate == 0)
                *new_rate = _dpll_compute_new_rate(parent_rate, *m, n);

        return r;
}

/**
 * _omap2_dpll_is_in_bypass - check if DPLL is in bypass mode or not
 * @v: bitfield value of the DPLL enable
 *
 * Checks given DPLL enable bitfield to see whether the DPLL is in bypass
 * mode or not. Returns 1 if the DPLL is in bypass, 0 otherwise.
 */
static int _omap2_dpll_is_in_bypass(u32 v)
{
        u8 mask, val;

        mask = ti_clk_get_features()->dpll_bypass_vals;

        /*
         * Each set bit in the mask corresponds to a bypass value equal
         * to the bitshift. Go through each set-bit in the mask and
         * compare against the given register value.
         */
        while (mask) {
                val = __ffs(mask);
                mask ^= (1 << val);
                if (v == val)
                        return 1;
        }

        return 0;
}

/* Public functions */
u8 omap2_init_dpll_parent(struct clk_hw *hw)
{
        struct clk_hw_omap *clk = to_clk_hw_omap(hw);
        u32 v;
        struct dpll_data *dd;

        dd = clk->dpll_data;
        if (!dd)
                return -EINVAL;

        v = ti_clk_ll_ops->clk_readl(dd->control_reg);
        v &= dd->enable_mask;
        v >>= __ffs(dd->enable_mask);

        /* Reparent the struct clk in case the dpll is in bypass */
        if (_omap2_dpll_is_in_bypass(v))
                return 1;

        return 0;
}

/**
 * omap2_get_dpll_rate - returns the current DPLL CLKOUT rate
 * @clk: struct clk * of a DPLL
 *
 * DPLLs can be locked or bypassed - basically, enabled or disabled.
 * When locked, the DPLL output depends on the M and N values.  When
 * bypassed, on OMAP2xxx, the output rate is either the 32KiHz clock
 * or sys_clk.  Bypass rates on OMAP3 depend on the DPLL: DPLLs 1 and
 * 2 are bypassed with dpll1_fclk and dpll2_fclk respectively
 * (generated by DPLL3), while DPLL 3, 4, and 5 bypass rates are sys_clk.
 * Returns the current DPLL CLKOUT rate (*not* CLKOUTX2) if the DPLL is
 * locked, or the appropriate bypass rate if the DPLL is bypassed, or 0
 * if the clock @clk is not a DPLL.
 */
unsigned long omap2_get_dpll_rate(struct clk_hw_omap *clk)
{
        u64 dpll_clk;
        u32 dpll_mult, dpll_div, v;
        struct dpll_data *dd;

        dd = clk->dpll_data;
        if (!dd)
                return 0;

        /* Return bypass rate if DPLL is bypassed */
        v = ti_clk_ll_ops->clk_readl(dd->control_reg);
        v &= dd->enable_mask;
        v >>= __ffs(dd->enable_mask);

        if (_omap2_dpll_is_in_bypass(v))
                return clk_hw_get_rate(dd->clk_bypass);

        v = ti_clk_ll_ops->clk_readl(dd->mult_div1_reg);
        dpll_mult = v & dd->mult_mask;
        dpll_mult >>= __ffs(dd->mult_mask);
        dpll_div = v & dd->div1_mask;
        dpll_div >>= __ffs(dd->div1_mask);

        dpll_clk = (u64)clk_hw_get_rate(dd->clk_ref) * dpll_mult;
        do_div(dpll_clk, dpll_div + 1);

        return dpll_clk;
}

/* DPLL rate rounding code */

/**
 * omap2_dpll_round_rate - round a target rate for an OMAP DPLL
 * @clk: struct clk * for a DPLL
 * @target_rate: desired DPLL clock rate
 *
 * Given a DPLL and a desired target rate, round the target rate to a
 * possible, programmable rate for this DPLL.  Attempts to select the
 * minimum possible n.  Stores the computed (m, n) in the DPLL's
 * dpll_data structure so set_rate() will not need to call this
 * (expensive) function again.  Returns ~0 if the target rate cannot
 * be rounded, or the rounded rate upon success.
 */
long omap2_dpll_round_rate(struct clk_hw *hw, unsigned long target_rate,
                           unsigned long *parent_rate)
{
        struct clk_hw_omap *clk = to_clk_hw_omap(hw);
        int m, n, r, scaled_max_m;
        int min_delta_m = INT_MAX, min_delta_n = INT_MAX;
        unsigned long scaled_rt_rp;
        unsigned long new_rate = 0;
        struct dpll_data *dd;
        unsigned long ref_rate;
        long delta;
        long prev_min_delta = LONG_MAX;
        const char *clk_name;

        if (!clk || !clk->dpll_data)
                return ~0;

        dd = clk->dpll_data;

        if (dd->max_rate && target_rate > dd->max_rate)
                target_rate = dd->max_rate;

        ref_rate = clk_hw_get_rate(dd->clk_ref);
        clk_name = clk_hw_get_name(hw);
        pr_debug("clock: %s: starting DPLL round_rate, target rate %lu\n",
                 clk_name, target_rate);

        scaled_rt_rp = target_rate / (ref_rate / DPLL_SCALE_FACTOR);
        scaled_max_m = dd->max_multiplier * DPLL_SCALE_FACTOR;

        dd->last_rounded_rate = 0;

        for (n = dd->min_divider; n <= dd->max_divider; n++) {
                /* Is the (input clk, divider) pair valid for the DPLL? */
                r = _dpll_test_fint(clk, n);
                if (r == DPLL_FINT_UNDERFLOW)
                        break;
                else if (r == DPLL_FINT_INVALID)
                        continue;

                /* Compute the scaled DPLL multiplier, based on the divider */
                m = scaled_rt_rp * n;

                /*
                 * Since we're counting n up, a m overflow means we
                 * can bail out completely (since as n increases in
                 * the next iteration, there's no way that m can
                 * increase beyond the current m)
                 */
                if (m > scaled_max_m)
                        break;

                r = _dpll_test_mult(&m, n, &new_rate, target_rate,
                                    ref_rate);

                /* m can't be set low enough for this n - try with a larger n */
                if (r == DPLL_MULT_UNDERFLOW)
                        continue;

                /* skip rates above our target rate */
                delta = target_rate - new_rate;
                if (delta < 0)
                        continue;

                if (delta < prev_min_delta) {
                        prev_min_delta = delta;
                        min_delta_m = m;
                        min_delta_n = n;
                }

                pr_debug("clock: %s: m = %d: n = %d: new_rate = %lu\n",
                         clk_name, m, n, new_rate);

                if (delta == 0)
                        break;
        }

        if (prev_min_delta == LONG_MAX) {
                pr_debug("clock: %s: cannot round to rate %lu\n",
                         clk_name, target_rate);
                return ~0;
        }

        dd->last_rounded_m = min_delta_m;
        dd->last_rounded_n = min_delta_n;
        dd->last_rounded_rate = target_rate - prev_min_delta;

        return dd->last_rounded_rate;
}