/*
 * drivers/media/i2c/smiapp-pll.c
 *
 * Generic driver for SMIA/SMIA++ compliant camera modules
 *
 * Copyright (C) 2011--2012 Nokia Corporation
 * Contact: Sakari Ailus <sakari.ailus@iki.fi>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/device.h>
#include <linux/gcd.h>
#include <linux/lcm.h>
#include <linux/module.h>

#include "smiapp-pll.h"

/* Return an even number or one. */
static inline uint32_t clk_div_even(uint32_t a)
{
        return max_t(uint32_t, 1, a & ~1);
}

/* Return an even number or one. */
static inline uint32_t clk_div_even_up(uint32_t a)
{
        if (a == 1)
                return 1;
        return (a + 1) & ~1;
}

static inline uint32_t is_one_or_even(uint32_t a)
{
        if (a == 1)
                return 1;
        if (a & 1)
                return 0;

        return 1;
}

static int bounds_check(struct device *dev, uint32_t val,
                        uint32_t min, uint32_t max, char *str)
{
        if (val >= min && val <= max)
                return 0;

        dev_dbg(dev, "%s out of bounds: %d (%d--%d)\n", str, val, min, max);

        return -EINVAL;
}

static void print_pll(struct device *dev, struct smiapp_pll *pll)
{
        dev_dbg(dev, "pre_pll_clk_div\t%u\n",  pll->pre_pll_clk_div);
        dev_dbg(dev, "pll_multiplier \t%u\n",  pll->pll_multiplier);
        if (!(pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS)) {
                dev_dbg(dev, "op_sys_clk_div \t%u\n", pll->op.sys_clk_div);
                dev_dbg(dev, "op_pix_clk_div \t%u\n", pll->op.pix_clk_div);
        }
        dev_dbg(dev, "vt_sys_clk_div \t%u\n",  pll->vt.sys_clk_div);
        dev_dbg(dev, "vt_pix_clk_div \t%u\n",  pll->vt.pix_clk_div);

        dev_dbg(dev, "ext_clk_freq_hz \t%u\n", pll->ext_clk_freq_hz);
        dev_dbg(dev, "pll_ip_clk_freq_hz \t%u\n", pll->pll_ip_clk_freq_hz);
        dev_dbg(dev, "pll_op_clk_freq_hz \t%u\n", pll->pll_op_clk_freq_hz);
        if (!(pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS)) {
                dev_dbg(dev, "op_sys_clk_freq_hz \t%u\n",
                        pll->op.sys_clk_freq_hz);
                dev_dbg(dev, "op_pix_clk_freq_hz \t%u\n",
                        pll->op.pix_clk_freq_hz);
        }
        dev_dbg(dev, "vt_sys_clk_freq_hz \t%u\n", pll->vt.sys_clk_freq_hz);
        dev_dbg(dev, "vt_pix_clk_freq_hz \t%u\n", pll->vt.pix_clk_freq_hz);
}

static int check_all_bounds(struct device *dev,
                            const struct smiapp_pll_limits *limits,
                            const struct smiapp_pll_branch_limits *op_limits,
                            struct smiapp_pll *pll,
                            struct smiapp_pll_branch *op_pll)
{
        int rval;

        rval = bounds_check(dev, pll->pll_ip_clk_freq_hz,
                            limits->min_pll_ip_freq_hz,
                            limits->max_pll_ip_freq_hz,
                            "pll_ip_clk_freq_hz");
        if (!rval)
                rval = bounds_check(
                        dev, pll->pll_multiplier,
                        limits->min_pll_multiplier, limits->max_pll_multiplier,
                        "pll_multiplier");
        if (!rval)
                rval = bounds_check(
                        dev, pll->pll_op_clk_freq_hz,
                        limits->min_pll_op_freq_hz, limits->max_pll_op_freq_hz,
                        "pll_op_clk_freq_hz");
        if (!rval)
                rval = bounds_check(
                        dev, op_pll->sys_clk_div,
                        op_limits->min_sys_clk_div, op_limits->max_sys_clk_div,
                        "op_sys_clk_div");
        if (!rval)
                rval = bounds_check(
                        dev, op_pll->sys_clk_freq_hz,
                        op_limits->min_sys_clk_freq_hz,
                        op_limits->max_sys_clk_freq_hz,
                        "op_sys_clk_freq_hz");
        if (!rval)
                rval = bounds_check(
                        dev, op_pll->pix_clk_freq_hz,
                        op_limits->min_pix_clk_freq_hz,
                        op_limits->max_pix_clk_freq_hz,
                        "op_pix_clk_freq_hz");

        /*
         * If there are no OP clocks, the VT clocks are contained in
         * the OP clock struct.
         */
        if (pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS)
                return rval;

        if (!rval)
                rval = bounds_check(
                        dev, pll->vt.sys_clk_freq_hz,
                        limits->vt.min_sys_clk_freq_hz,
                        limits->vt.max_sys_clk_freq_hz,
                        "vt_sys_clk_freq_hz");
        if (!rval)
                rval = bounds_check(
                        dev, pll->vt.pix_clk_freq_hz,
                        limits->vt.min_pix_clk_freq_hz,
                        limits->vt.max_pix_clk_freq_hz,
                        "vt_pix_clk_freq_hz");

        return rval;
}

/*
 * Heuristically guess the PLL tree for a given common multiplier and
 * divisor. Begin with the operational timing and continue to video
 * timing once operational timing has been verified.
 *
 * @mul is the PLL multiplier and @div is the common divisor
 * (pre_pll_clk_div and op_sys_clk_div combined). The final PLL
 * multiplier will be a multiple of @mul.
 *
 * @return Zero on success, error code on error.
 */
static int __smiapp_pll_calculate(
        struct device *dev, const struct smiapp_pll_limits *limits,
        const struct smiapp_pll_branch_limits *op_limits,
        struct smiapp_pll *pll, struct smiapp_pll_branch *op_pll, uint32_t mul,
        uint32_t div, uint32_t lane_op_clock_ratio)
{
        uint32_t sys_div;
        uint32_t best_pix_div = INT_MAX >> 1;
        uint32_t vt_op_binning_div;
        /*
         * Higher multipliers (and divisors) are often required than
         * necessitated by the external clock and the output clocks.
         * There are limits for all values in the clock tree. These
         * are the minimum and maximum multiplier for mul.
         */
        uint32_t more_mul_min, more_mul_max;
        uint32_t more_mul_factor;
        uint32_t min_vt_div, max_vt_div, vt_div;
        uint32_t min_sys_div, max_sys_div;
        unsigned int i;

        /*
         * Get pre_pll_clk_div so that our pll_op_clk_freq_hz won't be
         * too high.
         */
        dev_dbg(dev, "pre_pll_clk_div %u\n", pll->pre_pll_clk_div);

        /* Don't go above max pll multiplier. */
        more_mul_max = limits->max_pll_multiplier / mul;
        dev_dbg(dev, "more_mul_max: max_pll_multiplier check: %u\n",
                more_mul_max);
        /* Don't go above max pll op frequency. */
        more_mul_max =
                min_t(uint32_t,
                      more_mul_max,
                      limits->max_pll_op_freq_hz
                      / (pll->ext_clk_freq_hz / pll->pre_pll_clk_div * mul));
        dev_dbg(dev, "more_mul_max: max_pll_op_freq_hz check: %u\n",
                more_mul_max);
        /* Don't go above the division capability of op sys clock divider. */
        more_mul_max = min(more_mul_max,
                           op_limits->max_sys_clk_div * pll->pre_pll_clk_div
                           / div);
        dev_dbg(dev, "more_mul_max: max_op_sys_clk_div check: %u\n",
                more_mul_max);
        /* Ensure we won't go above min_pll_multiplier. */
        more_mul_max = min(more_mul_max,
                           DIV_ROUND_UP(limits->max_pll_multiplier, mul));
        dev_dbg(dev, "more_mul_max: min_pll_multiplier check: %u\n",
                more_mul_max);

        /* Ensure we won't go below min_pll_op_freq_hz. */
        more_mul_min = DIV_ROUND_UP(limits->min_pll_op_freq_hz,
                                    pll->ext_clk_freq_hz / pll->pre_pll_clk_div
                                    * mul);
        dev_dbg(dev, "more_mul_min: min_pll_op_freq_hz check: %u\n",
                more_mul_min);
        /* Ensure we won't go below min_pll_multiplier. */
        more_mul_min = max(more_mul_min,
                           DIV_ROUND_UP(limits->min_pll_multiplier, mul));
        dev_dbg(dev, "more_mul_min: min_pll_multiplier check: %u\n",
                more_mul_min);

        if (more_mul_min > more_mul_max) {
                dev_dbg(dev,
                        "unable to compute more_mul_min and more_mul_max\n");
                return -EINVAL;
        }

        more_mul_factor = lcm(div, pll->pre_pll_clk_div) / div;
        dev_dbg(dev, "more_mul_factor: %u\n", more_mul_factor);
        more_mul_factor = lcm(more_mul_factor, op_limits->min_sys_clk_div);
        dev_dbg(dev, "more_mul_factor: min_op_sys_clk_div: %d\n",
                more_mul_factor);
        i = roundup(more_mul_min, more_mul_factor);
        if (!is_one_or_even(i))
                i <<= 1;

        dev_dbg(dev, "final more_mul: %u\n", i);
        if (i > more_mul_max) {
                dev_dbg(dev, "final more_mul is bad, max %u\n", more_mul_max);
                return -EINVAL;
        }

        pll->pll_multiplier = mul * i;
        op_pll->sys_clk_div = div * i / pll->pre_pll_clk_div;
        dev_dbg(dev, "op_sys_clk_div: %u\n", op_pll->sys_clk_div);

        pll->pll_ip_clk_freq_hz = pll->ext_clk_freq_hz
                / pll->pre_pll_clk_div;

        pll->pll_op_clk_freq_hz = pll->pll_ip_clk_freq_hz
                * pll->pll_multiplier;

        /* Derive pll_op_clk_freq_hz. */
        op_pll->sys_clk_freq_hz =
                pll->pll_op_clk_freq_hz / op_pll->sys_clk_div;

        op_pll->pix_clk_div = pll->bits_per_pixel;
        dev_dbg(dev, "op_pix_clk_div: %u\n", op_pll->pix_clk_div);

        op_pll->pix_clk_freq_hz =
                op_pll->sys_clk_freq_hz / op_pll->pix_clk_div;

        if (pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS) {
                /* No OP clocks --- VT clocks are used instead. */
                goto out_skip_vt_calc;
        }

        /*
         * Some sensors perform analogue binning and some do this
         * digitally. The ones doing this digitally can be roughly be
         * found out using this formula. The ones doing this digitally
         * should run at higher clock rate, so smaller divisor is used
         * on video timing side.
         */
        if (limits->min_line_length_pck_bin > limits->min_line_length_pck
            / pll->binning_horizontal)
                vt_op_binning_div = pll->binning_horizontal;
        else
                vt_op_binning_div = 1;
        dev_dbg(dev, "vt_op_binning_div: %u\n", vt_op_binning_div);

        /*
         * Profile 2 supports vt_pix_clk_div E [4, 10]
         *
         * Horizontal binning can be used as a base for difference in
         * divisors. One must make sure that horizontal blanking is
         * enough to accommodate the CSI-2 sync codes.
         *
         * Take scaling factor into account as well.
         *
         * Find absolute limits for the factor of vt divider.
         */
        dev_dbg(dev, "scale_m: %u\n", pll->scale_m);
        min_vt_div = DIV_ROUND_UP(op_pll->pix_clk_div * op_pll->sys_clk_div
                                  * pll->scale_n,
                                  lane_op_clock_ratio * vt_op_binning_div
                                  * pll->scale_m);

        /* Find smallest and biggest allowed vt divisor. */
        dev_dbg(dev, "min_vt_div: %u\n", min_vt_div);
        min_vt_div = max(min_vt_div,
                         DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
                                      limits->vt.max_pix_clk_freq_hz));
        dev_dbg(dev, "min_vt_div: max_vt_pix_clk_freq_hz: %u\n",
                min_vt_div);
        min_vt_div = max_t(uint32_t, min_vt_div,
                           limits->vt.min_pix_clk_div
                           * limits->vt.min_sys_clk_div);
        dev_dbg(dev, "min_vt_div: min_vt_clk_div: %u\n", min_vt_div);

        max_vt_div = limits->vt.max_sys_clk_div * limits->vt.max_pix_clk_div;
        dev_dbg(dev, "max_vt_div: %u\n", max_vt_div);
        max_vt_div = min(max_vt_div,
                         DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
                                      limits->vt.min_pix_clk_freq_hz));
        dev_dbg(dev, "max_vt_div: min_vt_pix_clk_freq_hz: %u\n",
                max_vt_div);

        /*
         * Find limitsits for sys_clk_div. Not all values are possible
         * with all values of pix_clk_div.
         */
        min_sys_div = limits->vt.min_sys_clk_div;
        dev_dbg(dev, "min_sys_div: %u\n", min_sys_div);
        min_sys_div = max(min_sys_div,
                          DIV_ROUND_UP(min_vt_div,
                                       limits->vt.max_pix_clk_div));
        dev_dbg(dev, "min_sys_div: max_vt_pix_clk_div: %u\n", min_sys_div);
        min_sys_div = max(min_sys_div,
                          pll->pll_op_clk_freq_hz
                          / limits->vt.max_sys_clk_freq_hz);
        dev_dbg(dev, "min_sys_div: max_pll_op_clk_freq_hz: %u\n", min_sys_div);
        min_sys_div = clk_div_even_up(min_sys_div);
        dev_dbg(dev, "min_sys_div: one or even: %u\n", min_sys_div);

        max_sys_div = limits->vt.max_sys_clk_div;
        dev_dbg(dev, "max_sys_div: %u\n", max_sys_div);
        max_sys_div = min(max_sys_div,
                          DIV_ROUND_UP(max_vt_div,
                                       limits->vt.min_pix_clk_div));
        dev_dbg(dev, "max_sys_div: min_vt_pix_clk_div: %u\n", max_sys_div);
        max_sys_div = min(max_sys_div,
                          DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
                                       limits->vt.min_pix_clk_freq_hz));
        dev_dbg(dev, "max_sys_div: min_vt_pix_clk_freq_hz: %u\n", max_sys_div);

        /*
         * Find pix_div such that a legal pix_div * sys_div results
         * into a value which is not smaller than div, the desired
         * divisor.
         */
        for (vt_div = min_vt_div; vt_div <= max_vt_div;
             vt_div += 2 - (vt_div & 1)) {
                for (sys_div = min_sys_div;
                     sys_div <= max_sys_div;
                     sys_div += 2 - (sys_div & 1)) {
                        uint16_t pix_div = DIV_ROUND_UP(vt_div, sys_div);

                        if (pix_div < limits->vt.min_pix_clk_div
                            || pix_div > limits->vt.max_pix_clk_div) {
                                dev_dbg(dev,
                                        "pix_div %u too small or too big (%u--%u)\n",
                                        pix_div,
                                        limits->vt.min_pix_clk_div,
                                        limits->vt.max_pix_clk_div);
                                continue;
                        }

                        /* Check if this one is better. */
                        if (pix_div * sys_div
                            <= roundup(min_vt_div, best_pix_div))
                                best_pix_div = pix_div;
                }
                if (best_pix_div < INT_MAX >> 1)
                        break;
        }

        pll->vt.sys_clk_div = DIV_ROUND_UP(min_vt_div, best_pix_div);
        pll->vt.pix_clk_div = best_pix_div;

        pll->vt.sys_clk_freq_hz =
                pll->pll_op_clk_freq_hz / pll->vt.sys_clk_div;
        pll->vt.pix_clk_freq_hz =
                pll->vt.sys_clk_freq_hz / pll->vt.pix_clk_div;

out_skip_vt_calc:
        pll->pixel_rate_csi =
                op_pll->pix_clk_freq_hz * lane_op_clock_ratio;
        pll->pixel_rate_pixel_array = pll->vt.pix_clk_freq_hz;

        return check_all_bounds(dev, limits, op_limits, pll, op_pll);
}

int smiapp_pll_calculate(struct device *dev,
                         const struct smiapp_pll_limits *limits,
                         struct smiapp_pll *pll)
{
        const struct smiapp_pll_branch_limits *op_limits = &limits->op;
        struct smiapp_pll_branch *op_pll = &pll->op;
        uint16_t min_pre_pll_clk_div;
        uint16_t max_pre_pll_clk_div;
        uint32_t lane_op_clock_ratio;
        uint32_t mul, div;
        unsigned int i;
        int rval = -EINVAL;

        if (pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS) {
                /*
                 * If there's no OP PLL at all, use the VT values
                 * instead. The OP values are ignored for the rest of
                 * the PLL calculation.
                 */
                op_limits = &limits->vt;
                op_pll = &pll->vt;
        }

        if (pll->flags & SMIAPP_PLL_FLAG_OP_PIX_CLOCK_PER_LANE)
                lane_op_clock_ratio = pll->csi2.lanes;
        else
                lane_op_clock_ratio = 1;
        dev_dbg(dev, "lane_op_clock_ratio: %u\n", lane_op_clock_ratio);

        dev_dbg(dev, "binning: %ux%u\n", pll->binning_horizontal,
                pll->binning_vertical);

        switch (pll->bus_type) {
        case SMIAPP_PLL_BUS_TYPE_CSI2:
                /* CSI transfers 2 bits per clock per lane; thus times 2 */
                pll->pll_op_clk_freq_hz = pll->link_freq * 2
                        * (pll->csi2.lanes / lane_op_clock_ratio);
                break;
        case SMIAPP_PLL_BUS_TYPE_PARALLEL:
                pll->pll_op_clk_freq_hz = pll->link_freq * pll->bits_per_pixel
                        / DIV_ROUND_UP(pll->bits_per_pixel,
                                       pll->parallel.bus_width);
                break;
        default:
                return -EINVAL;
        }

        /* Figure out limits for pre-pll divider based on extclk */
        dev_dbg(dev, "min / max pre_pll_clk_div: %u / %u\n",
                limits->min_pre_pll_clk_div, limits->max_pre_pll_clk_div);
        max_pre_pll_clk_div =
                min_t(uint16_t, limits->max_pre_pll_clk_div,
                      clk_div_even(pll->ext_clk_freq_hz /
                                   limits->min_pll_ip_freq_hz));
        min_pre_pll_clk_div =
                max_t(uint16_t, limits->min_pre_pll_clk_div,
                      clk_div_even_up(
                              DIV_ROUND_UP(pll->ext_clk_freq_hz,
                                           limits->max_pll_ip_freq_hz)));
        dev_dbg(dev, "pre-pll check: min / max pre_pll_clk_div: %u / %u\n",
                min_pre_pll_clk_div, max_pre_pll_clk_div);

        i = gcd(pll->pll_op_clk_freq_hz, pll->ext_clk_freq_hz);
        mul = div_u64(pll->pll_op_clk_freq_hz, i);
        div = pll->ext_clk_freq_hz / i;
        dev_dbg(dev, "mul %u / div %u\n", mul, div);

        min_pre_pll_clk_div =
                max_t(uint16_t, min_pre_pll_clk_div,
                      clk_div_even_up(
                              DIV_ROUND_UP(mul * pll->ext_clk_freq_hz,
                                           limits->max_pll_op_freq_hz)));
        dev_dbg(dev, "pll_op check: min / max pre_pll_clk_div: %u / %u\n",
                min_pre_pll_clk_div, max_pre_pll_clk_div);

        for (pll->pre_pll_clk_div = min_pre_pll_clk_div;
             pll->pre_pll_clk_div <= max_pre_pll_clk_div;
             pll->pre_pll_clk_div += 2 - (pll->pre_pll_clk_div & 1)) {
                rval = __smiapp_pll_calculate(dev, limits, op_limits, pll,
                                              op_pll, mul, div,
                                              lane_op_clock_ratio);
                if (rval)
                        continue;

                print_pll(dev, pll);
                return 0;
        }

        dev_dbg(dev, "unable to compute pre_pll divisor\n");

        return rval;
}
EXPORT_SYMBOL_GPL(smiapp_pll_calculate);

MODULE_AUTHOR("Sakari Ailus <sakari.ailus@iki.fi>");
MODULE_DESCRIPTION("Generic SMIA/SMIA++ PLL calculator");
MODULE_LICENSE("GPL");