// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
 *
 * Authors:
 *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
 *   Dmitry Dunaev <dmitry.dunaev@baikalelectronics.ru>
 *
 * Baikal-T1 CCU PLL interface driver
 */

#define pr_fmt(fmt) "bt1-ccu-pll: " fmt

#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/limits.h>
#include <linux/bits.h>
#include <linux/bitfield.h>
#include <linux/slab.h>
#include <linux/clk-provider.h>
#include <linux/of.h>
#include <linux/spinlock.h>
#include <linux/regmap.h>
#include <linux/iopoll.h>
#include <linux/time64.h>
#include <linux/rational.h>
#include <linux/debugfs.h>

#include "ccu-pll.h"

#define CCU_PLL_CTL                     0x000
#define CCU_PLL_CTL_EN                  BIT(0)
#define CCU_PLL_CTL_RST                 BIT(1)
#define CCU_PLL_CTL_CLKR_FLD            2
#define CCU_PLL_CTL_CLKR_MASK           GENMASK(7, CCU_PLL_CTL_CLKR_FLD)
#define CCU_PLL_CTL_CLKF_FLD            8
#define CCU_PLL_CTL_CLKF_MASK           GENMASK(20, CCU_PLL_CTL_CLKF_FLD)
#define CCU_PLL_CTL_CLKOD_FLD           21
#define CCU_PLL_CTL_CLKOD_MASK          GENMASK(24, CCU_PLL_CTL_CLKOD_FLD)
#define CCU_PLL_CTL_BYPASS              BIT(30)
#define CCU_PLL_CTL_LOCK                BIT(31)
#define CCU_PLL_CTL1                    0x004
#define CCU_PLL_CTL1_BWADJ_FLD          3
#define CCU_PLL_CTL1_BWADJ_MASK         GENMASK(14, CCU_PLL_CTL1_BWADJ_FLD)

#define CCU_PLL_LOCK_CHECK_RETRIES      50

#define CCU_PLL_NR_MAX \
        ((CCU_PLL_CTL_CLKR_MASK >> CCU_PLL_CTL_CLKR_FLD) + 1)
#define CCU_PLL_NF_MAX \
        ((CCU_PLL_CTL_CLKF_MASK >> (CCU_PLL_CTL_CLKF_FLD + 1)) + 1)
#define CCU_PLL_OD_MAX \
        ((CCU_PLL_CTL_CLKOD_MASK >> CCU_PLL_CTL_CLKOD_FLD) + 1)
#define CCU_PLL_NB_MAX \
        ((CCU_PLL_CTL1_BWADJ_MASK >> CCU_PLL_CTL1_BWADJ_FLD) + 1)
#define CCU_PLL_FDIV_MIN                427000UL
#define CCU_PLL_FDIV_MAX                3500000000UL
#define CCU_PLL_FOUT_MIN                200000000UL
#define CCU_PLL_FOUT_MAX                2500000000UL
#define CCU_PLL_FVCO_MIN                700000000UL
#define CCU_PLL_FVCO_MAX                3500000000UL
#define CCU_PLL_CLKOD_FACTOR            2

static inline unsigned long ccu_pll_lock_delay_us(unsigned long ref_clk,
                                                  unsigned long nr)
{
        u64 us = 500ULL * nr * USEC_PER_SEC;

        do_div(us, ref_clk);

        return us;
}

static inline unsigned long ccu_pll_calc_freq(unsigned long ref_clk,
                                              unsigned long nr,
                                              unsigned long nf,
                                              unsigned long od)
{
        u64 tmp = ref_clk;

        do_div(tmp, nr);
        tmp *= nf;
        do_div(tmp, od);

        return tmp;
}

static int ccu_pll_reset(struct ccu_pll *pll, unsigned long ref_clk,
                         unsigned long nr)
{
        unsigned long ud, ut;
        u32 val;

        ud = ccu_pll_lock_delay_us(ref_clk, nr);
        ut = ud * CCU_PLL_LOCK_CHECK_RETRIES;

        regmap_update_bits(pll->sys_regs, pll->reg_ctl,
                           CCU_PLL_CTL_RST, CCU_PLL_CTL_RST);

        return regmap_read_poll_timeout_atomic(pll->sys_regs, pll->reg_ctl, val,
                                               val & CCU_PLL_CTL_LOCK, ud, ut);
}

static int ccu_pll_enable(struct clk_hw *hw)
{
        struct clk_hw *parent_hw = clk_hw_get_parent(hw);
        struct ccu_pll *pll = to_ccu_pll(hw);
        unsigned long flags;
        u32 val = 0;
        int ret;

        if (!parent_hw) {
                pr_err("Can't enable '%s' with no parent", clk_hw_get_name(hw));
                return -EINVAL;
        }

        regmap_read(pll->sys_regs, pll->reg_ctl, &val);
        if (val & CCU_PLL_CTL_EN)
                return 0;

        spin_lock_irqsave(&pll->lock, flags);
        regmap_write(pll->sys_regs, pll->reg_ctl, val | CCU_PLL_CTL_EN);
        ret = ccu_pll_reset(pll, clk_hw_get_rate(parent_hw),
                            FIELD_GET(CCU_PLL_CTL_CLKR_MASK, val) + 1);
        spin_unlock_irqrestore(&pll->lock, flags);
        if (ret)
                pr_err("PLL '%s' reset timed out\n", clk_hw_get_name(hw));

        return ret;
}

static void ccu_pll_disable(struct clk_hw *hw)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        unsigned long flags;

        spin_lock_irqsave(&pll->lock, flags);
        regmap_update_bits(pll->sys_regs, pll->reg_ctl, CCU_PLL_CTL_EN, 0);
        spin_unlock_irqrestore(&pll->lock, flags);
}

static int ccu_pll_is_enabled(struct clk_hw *hw)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        u32 val = 0;

        regmap_read(pll->sys_regs, pll->reg_ctl, &val);

        return !!(val & CCU_PLL_CTL_EN);
}

static unsigned long ccu_pll_recalc_rate(struct clk_hw *hw,
                                         unsigned long parent_rate)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        unsigned long nr, nf, od;
        u32 val = 0;

        regmap_read(pll->sys_regs, pll->reg_ctl, &val);
        nr = FIELD_GET(CCU_PLL_CTL_CLKR_MASK, val) + 1;
        nf = FIELD_GET(CCU_PLL_CTL_CLKF_MASK, val) + 1;
        od = FIELD_GET(CCU_PLL_CTL_CLKOD_MASK, val) + 1;

        return ccu_pll_calc_freq(parent_rate, nr, nf, od);
}

static void ccu_pll_calc_factors(unsigned long rate, unsigned long parent_rate,
                                 unsigned long *nr, unsigned long *nf,
                                 unsigned long *od)
{
        unsigned long err, freq, min_err = ULONG_MAX;
        unsigned long num, denom, n1, d1, nri;
        unsigned long nr_max, nf_max, od_max;

        /*
         * Make sure PLL is working with valid input signal (Fdiv). If
         * you want to speed the function up just reduce CCU_PLL_NR_MAX.
         * This will cause a worse approximation though.
         */
        nri = (parent_rate / CCU_PLL_FDIV_MAX) + 1;
        nr_max = min(parent_rate / CCU_PLL_FDIV_MIN, CCU_PLL_NR_MAX);

        /*
         * Find a closest [nr;nf;od] vector taking into account the
         * limitations like: 1) 700MHz <= Fvco <= 3.5GHz, 2) PLL Od is
         * either 1 or even number within the acceptable range (alas 1s
         * is also excluded by the next loop).
         */
        for (; nri <= nr_max; ++nri) {
                /* Use Od factor to fulfill the limitation 2). */
                num = CCU_PLL_CLKOD_FACTOR * rate;
                denom = parent_rate / nri;

                /*
                 * Make sure Fvco is within the acceptable range to fulfill
                 * the condition 1). Note due to the CCU_PLL_CLKOD_FACTOR value
                 * the actual upper limit is also divided by that factor.
                 * It's not big problem for us since practically there is no
                 * need in clocks with that high frequency.
                 */
                nf_max = min(CCU_PLL_FVCO_MAX / denom, CCU_PLL_NF_MAX);
                od_max = CCU_PLL_OD_MAX / CCU_PLL_CLKOD_FACTOR;

                /*
                 * Bypass the out-of-bound values, which can't be properly
                 * handled by the rational fraction approximation algorithm.
                 */
                if (num / denom >= nf_max) {
                        n1 = nf_max;
                        d1 = 1;
                } else if (denom / num >= od_max) {
                        n1 = 1;
                        d1 = od_max;
                } else {
                        rational_best_approximation(num, denom, nf_max, od_max,
                                                    &n1, &d1);
                }

                /* Select the best approximation of the target rate. */
                freq = ccu_pll_calc_freq(parent_rate, nri, n1, d1);
                err = abs((int64_t)freq - num);
                if (err < min_err) {
                        min_err = err;
                        *nr = nri;
                        *nf = n1;
                        *od = CCU_PLL_CLKOD_FACTOR * d1;
                }
        }
}

static long ccu_pll_round_rate(struct clk_hw *hw, unsigned long rate,
                               unsigned long *parent_rate)
{
        unsigned long nr = 1, nf = 1, od = 1;

        ccu_pll_calc_factors(rate, *parent_rate, &nr, &nf, &od);

        return ccu_pll_calc_freq(*parent_rate, nr, nf, od);
}

/*
 * This method is used for PLLs, which support the on-the-fly dividers
 * adjustment. So there is no need in gating such clocks.
 */
static int ccu_pll_set_rate_reset(struct clk_hw *hw, unsigned long rate,
                                  unsigned long parent_rate)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        unsigned long nr, nf, od;
        unsigned long flags;
        u32 mask, val;
        int ret;

        ccu_pll_calc_factors(rate, parent_rate, &nr, &nf, &od);

        mask = CCU_PLL_CTL_CLKR_MASK | CCU_PLL_CTL_CLKF_MASK |
               CCU_PLL_CTL_CLKOD_MASK;
        val = FIELD_PREP(CCU_PLL_CTL_CLKR_MASK, nr - 1) |
              FIELD_PREP(CCU_PLL_CTL_CLKF_MASK, nf - 1) |
              FIELD_PREP(CCU_PLL_CTL_CLKOD_MASK, od - 1);

        spin_lock_irqsave(&pll->lock, flags);
        regmap_update_bits(pll->sys_regs, pll->reg_ctl, mask, val);
        ret = ccu_pll_reset(pll, parent_rate, nr);
        spin_unlock_irqrestore(&pll->lock, flags);
        if (ret)
                pr_err("PLL '%s' reset timed out\n", clk_hw_get_name(hw));

        return ret;
}

/*
 * This method is used for PLLs, which don't support the on-the-fly dividers
 * adjustment. So the corresponding clocks are supposed to be gated first.
 */
static int ccu_pll_set_rate_norst(struct clk_hw *hw, unsigned long rate,
                                  unsigned long parent_rate)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        unsigned long nr, nf, od;
        unsigned long flags;
        u32 mask, val;

        ccu_pll_calc_factors(rate, parent_rate, &nr, &nf, &od);

        /*
         * Disable PLL if it was enabled by default or left enabled by the
         * system bootloader.
         */
        mask = CCU_PLL_CTL_CLKR_MASK | CCU_PLL_CTL_CLKF_MASK |
               CCU_PLL_CTL_CLKOD_MASK | CCU_PLL_CTL_EN;
        val = FIELD_PREP(CCU_PLL_CTL_CLKR_MASK, nr - 1) |
              FIELD_PREP(CCU_PLL_CTL_CLKF_MASK, nf - 1) |
              FIELD_PREP(CCU_PLL_CTL_CLKOD_MASK, od - 1);

        spin_lock_irqsave(&pll->lock, flags);
        regmap_update_bits(pll->sys_regs, pll->reg_ctl, mask, val);
        spin_unlock_irqrestore(&pll->lock, flags);

        return 0;
}

#ifdef CONFIG_DEBUG_FS

struct ccu_pll_dbgfs_bit {
        struct ccu_pll *pll;
        const char *name;
        unsigned int reg;
        u32 mask;
};

struct ccu_pll_dbgfs_fld {
        struct ccu_pll *pll;
        const char *name;
        unsigned int reg;
        unsigned int lsb;
        u32 mask;
        u32 min;
        u32 max;
};

#define CCU_PLL_DBGFS_BIT_ATTR(_name, _reg, _mask)      \
        {                                               \
                .name = _name,                          \
                .reg = _reg,                            \
                .mask = _mask                           \
        }

#define CCU_PLL_DBGFS_FLD_ATTR(_name, _reg, _lsb, _mask, _min, _max)    \
        {                                                               \
                .name = _name,                                          \
                .reg = _reg,                                            \
                .lsb = _lsb,                                            \
                .mask = _mask,                                          \
                .min = _min,                                            \
                .max = _max                                             \
        }

static const struct ccu_pll_dbgfs_bit ccu_pll_bits[] = {
        CCU_PLL_DBGFS_BIT_ATTR("pll_en", CCU_PLL_CTL, CCU_PLL_CTL_EN),
        CCU_PLL_DBGFS_BIT_ATTR("pll_rst", CCU_PLL_CTL, CCU_PLL_CTL_RST),
        CCU_PLL_DBGFS_BIT_ATTR("pll_bypass", CCU_PLL_CTL, CCU_PLL_CTL_BYPASS),
        CCU_PLL_DBGFS_BIT_ATTR("pll_lock", CCU_PLL_CTL, CCU_PLL_CTL_LOCK)
};

#define CCU_PLL_DBGFS_BIT_NUM   ARRAY_SIZE(ccu_pll_bits)

static const struct ccu_pll_dbgfs_fld ccu_pll_flds[] = {
        CCU_PLL_DBGFS_FLD_ATTR("pll_nr", CCU_PLL_CTL, CCU_PLL_CTL_CLKR_FLD,
                                CCU_PLL_CTL_CLKR_MASK, 1, CCU_PLL_NR_MAX),
        CCU_PLL_DBGFS_FLD_ATTR("pll_nf", CCU_PLL_CTL, CCU_PLL_CTL_CLKF_FLD,
                                CCU_PLL_CTL_CLKF_MASK, 1, CCU_PLL_NF_MAX),
        CCU_PLL_DBGFS_FLD_ATTR("pll_od", CCU_PLL_CTL, CCU_PLL_CTL_CLKOD_FLD,
                                CCU_PLL_CTL_CLKOD_MASK, 1, CCU_PLL_OD_MAX),
        CCU_PLL_DBGFS_FLD_ATTR("pll_nb", CCU_PLL_CTL1, CCU_PLL_CTL1_BWADJ_FLD,
                                CCU_PLL_CTL1_BWADJ_MASK, 1, CCU_PLL_NB_MAX)
};

#define CCU_PLL_DBGFS_FLD_NUM   ARRAY_SIZE(ccu_pll_flds)

/*
 * It can be dangerous to change the PLL settings behind clock framework back,
 * therefore we don't provide any kernel config based compile time option for
 * this feature to enable.
 */
#undef CCU_PLL_ALLOW_WRITE_DEBUGFS
#ifdef CCU_PLL_ALLOW_WRITE_DEBUGFS

static int ccu_pll_dbgfs_bit_set(void *priv, u64 val)
{
        const struct ccu_pll_dbgfs_bit *bit = priv;
        struct ccu_pll *pll = bit->pll;
        unsigned long flags;

        spin_lock_irqsave(&pll->lock, flags);
        regmap_update_bits(pll->sys_regs, pll->reg_ctl + bit->reg,
                           bit->mask, val ? bit->mask : 0);
        spin_unlock_irqrestore(&pll->lock, flags);

        return 0;
}

static int ccu_pll_dbgfs_fld_set(void *priv, u64 val)
{
        struct ccu_pll_dbgfs_fld *fld = priv;
        struct ccu_pll *pll = fld->pll;
        unsigned long flags;
        u32 data;

        val = clamp_t(u64, val, fld->min, fld->max);
        data = ((val - 1) << fld->lsb) & fld->mask;

        spin_lock_irqsave(&pll->lock, flags);
        regmap_update_bits(pll->sys_regs, pll->reg_ctl + fld->reg, fld->mask,
                           data);
        spin_unlock_irqrestore(&pll->lock, flags);

        return 0;
}

#define ccu_pll_dbgfs_mode      0644

#else /* !CCU_PLL_ALLOW_WRITE_DEBUGFS */

#define ccu_pll_dbgfs_bit_set   NULL
#define ccu_pll_dbgfs_fld_set   NULL
#define ccu_pll_dbgfs_mode      0444

#endif /* !CCU_PLL_ALLOW_WRITE_DEBUGFS */

static int ccu_pll_dbgfs_bit_get(void *priv, u64 *val)
{
        struct ccu_pll_dbgfs_bit *bit = priv;
        struct ccu_pll *pll = bit->pll;
        u32 data = 0;

        regmap_read(pll->sys_regs, pll->reg_ctl + bit->reg, &data);
        *val = !!(data & bit->mask);

        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(ccu_pll_dbgfs_bit_fops,
        ccu_pll_dbgfs_bit_get, ccu_pll_dbgfs_bit_set, "%llu\n");

static int ccu_pll_dbgfs_fld_get(void *priv, u64 *val)
{
        struct ccu_pll_dbgfs_fld *fld = priv;
        struct ccu_pll *pll = fld->pll;
        u32 data = 0;

        regmap_read(pll->sys_regs, pll->reg_ctl + fld->reg, &data);
        *val = ((data & fld->mask) >> fld->lsb) + 1;

        return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(ccu_pll_dbgfs_fld_fops,
        ccu_pll_dbgfs_fld_get, ccu_pll_dbgfs_fld_set, "%llu\n");

static void ccu_pll_debug_init(struct clk_hw *hw, struct dentry *dentry)
{
        struct ccu_pll *pll = to_ccu_pll(hw);
        struct ccu_pll_dbgfs_bit *bits;
        struct ccu_pll_dbgfs_fld *flds;
        int idx;

        bits = kcalloc(CCU_PLL_DBGFS_BIT_NUM, sizeof(*bits), GFP_KERNEL);
        if (!bits)
                return;

        for (idx = 0; idx < CCU_PLL_DBGFS_BIT_NUM; ++idx) {
                bits[idx] = ccu_pll_bits[idx];
                bits[idx].pll = pll;

                debugfs_create_file_unsafe(bits[idx].name, ccu_pll_dbgfs_mode,
                                           dentry, &bits[idx],
                                           &ccu_pll_dbgfs_bit_fops);
        }

        flds = kcalloc(CCU_PLL_DBGFS_FLD_NUM, sizeof(*flds), GFP_KERNEL);
        if (!flds)
                return;

        for (idx = 0; idx < CCU_PLL_DBGFS_FLD_NUM; ++idx) {
                flds[idx] = ccu_pll_flds[idx];
                flds[idx].pll = pll;

                debugfs_create_file_unsafe(flds[idx].name, ccu_pll_dbgfs_mode,
                                           dentry, &flds[idx],
                                           &ccu_pll_dbgfs_fld_fops);
        }
}

#else /* !CONFIG_DEBUG_FS */

#define ccu_pll_debug_init NULL

#endif /* !CONFIG_DEBUG_FS */

static const struct clk_ops ccu_pll_gate_to_set_ops = {
        .enable = ccu_pll_enable,
        .disable = ccu_pll_disable,
        .is_enabled = ccu_pll_is_enabled,
        .recalc_rate = ccu_pll_recalc_rate,
        .round_rate = ccu_pll_round_rate,
        .set_rate = ccu_pll_set_rate_norst,
        .debug_init = ccu_pll_debug_init
};

static const struct clk_ops ccu_pll_straight_set_ops = {
        .enable = ccu_pll_enable,
        .disable = ccu_pll_disable,
        .is_enabled = ccu_pll_is_enabled,
        .recalc_rate = ccu_pll_recalc_rate,
        .round_rate = ccu_pll_round_rate,
        .set_rate = ccu_pll_set_rate_reset,
        .debug_init = ccu_pll_debug_init
};

struct ccu_pll *ccu_pll_hw_register(const struct ccu_pll_init_data *pll_init)
{
        struct clk_parent_data parent_data = { };
        struct clk_init_data hw_init = { };
        struct ccu_pll *pll;
        int ret;

        if (!pll_init)
                return ERR_PTR(-EINVAL);

        pll = kzalloc(sizeof(*pll), GFP_KERNEL);
        if (!pll)
                return ERR_PTR(-ENOMEM);

        /*
         * Note since Baikal-T1 System Controller registers are MMIO-backed
         * we won't check the regmap IO operations return status, because it
         * must be zero anyway.
         */
        pll->hw.init = &hw_init;
        pll->reg_ctl = pll_init->base + CCU_PLL_CTL;
        pll->reg_ctl1 = pll_init->base + CCU_PLL_CTL1;
        pll->sys_regs = pll_init->sys_regs;
        pll->id = pll_init->id;
        spin_lock_init(&pll->lock);

        hw_init.name = pll_init->name;
        hw_init.flags = pll_init->flags;

        if (hw_init.flags & CLK_SET_RATE_GATE)
                hw_init.ops = &ccu_pll_gate_to_set_ops;
        else
                hw_init.ops = &ccu_pll_straight_set_ops;

        if (!pll_init->parent_name) {
                ret = -EINVAL;
                goto err_free_pll;
        }
        parent_data.fw_name = pll_init->parent_name;
        hw_init.parent_data = &parent_data;
        hw_init.num_parents = 1;

        ret = of_clk_hw_register(pll_init->np, &pll->hw);
        if (ret)
                goto err_free_pll;

        return pll;

err_free_pll:
        kfree(pll);

        return ERR_PTR(ret);
}

void ccu_pll_hw_unregister(struct ccu_pll *pll)
{
        clk_hw_unregister(&pll->hw);

        kfree(pll);
}