/*
 * Copyright (c) 2015, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only 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/bitops.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/pm_domain.h>
#include <linux/regmap.h>
#include <linux/reset-controller.h>
#include <linux/slab.h>
#include "gdsc.h"

#define PWR_ON_MASK             BIT(31)
#define EN_REST_WAIT_MASK       GENMASK_ULL(23, 20)
#define EN_FEW_WAIT_MASK        GENMASK_ULL(19, 16)
#define CLK_DIS_WAIT_MASK       GENMASK_ULL(15, 12)
#define SW_OVERRIDE_MASK        BIT(2)
#define HW_CONTROL_MASK         BIT(1)
#define SW_COLLAPSE_MASK        BIT(0)
#define GMEM_CLAMP_IO_MASK      BIT(0)

/* Wait 2^n CXO cycles between all states. Here, n=2 (4 cycles). */
#define EN_REST_WAIT_VAL        (0x2 << 20)
#define EN_FEW_WAIT_VAL         (0x8 << 16)
#define CLK_DIS_WAIT_VAL        (0x2 << 12)

#define RETAIN_MEM              BIT(14)
#define RETAIN_PERIPH           BIT(13)

#define TIMEOUT_US              100

#define domain_to_gdsc(domain) container_of(domain, struct gdsc, pd)

static int gdsc_is_enabled(struct gdsc *sc, unsigned int reg)
{
        u32 val;
        int ret;

        ret = regmap_read(sc->regmap, reg, &val);
        if (ret)
                return ret;

        return !!(val & PWR_ON_MASK);
}

static int gdsc_hwctrl(struct gdsc *sc, bool en)
{
        u32 val = en ? HW_CONTROL_MASK : 0;

        return regmap_update_bits(sc->regmap, sc->gdscr, HW_CONTROL_MASK, val);
}

static int gdsc_poll_status(struct gdsc *sc, unsigned int reg, bool en)
{
        ktime_t start;

        start = ktime_get();
        do {
                if (gdsc_is_enabled(sc, reg) == en)
                        return 0;
        } while (ktime_us_delta(ktime_get(), start) < TIMEOUT_US);

        if (gdsc_is_enabled(sc, reg) == en)
                return 0;

        return -ETIMEDOUT;
}

static int gdsc_toggle_logic(struct gdsc *sc, bool en)
{
        int ret;
        u32 val = en ? 0 : SW_COLLAPSE_MASK;
        unsigned int status_reg = sc->gdscr;

        ret = regmap_update_bits(sc->regmap, sc->gdscr, SW_COLLAPSE_MASK, val);
        if (ret)
                return ret;

        /* If disabling votable gdscs, don't poll on status */
        if ((sc->flags & VOTABLE) && !en) {
                /*
                 * Add a short delay here to ensure that an enable
                 * right after it was disabled does not put it in an
                 * unknown state
                 */
                udelay(TIMEOUT_US);
                return 0;
        }

        if (sc->gds_hw_ctrl) {
                status_reg = sc->gds_hw_ctrl;
                /*
                 * The gds hw controller asserts/de-asserts the status bit soon
                 * after it receives a power on/off request from a master.
                 * The controller then takes around 8 xo cycles to start its
                 * internal state machine and update the status bit. During
                 * this time, the status bit does not reflect the true status
                 * of the core.
                 * Add a delay of 1 us between writing to the SW_COLLAPSE bit
                 * and polling the status bit.
                 */
                udelay(1);
        }

        return gdsc_poll_status(sc, status_reg, en);
}

static inline int gdsc_deassert_reset(struct gdsc *sc)
{
        int i;

        for (i = 0; i < sc->reset_count; i++)
                sc->rcdev->ops->deassert(sc->rcdev, sc->resets[i]);
        return 0;
}

static inline int gdsc_assert_reset(struct gdsc *sc)
{
        int i;

        for (i = 0; i < sc->reset_count; i++)
                sc->rcdev->ops->assert(sc->rcdev, sc->resets[i]);
        return 0;
}

static inline void gdsc_force_mem_on(struct gdsc *sc)
{
        int i;
        u32 mask = RETAIN_MEM | RETAIN_PERIPH;

        for (i = 0; i < sc->cxc_count; i++)
                regmap_update_bits(sc->regmap, sc->cxcs[i], mask, mask);
}

static inline void gdsc_clear_mem_on(struct gdsc *sc)
{
        int i;
        u32 mask = RETAIN_MEM | RETAIN_PERIPH;

        for (i = 0; i < sc->cxc_count; i++)
                regmap_update_bits(sc->regmap, sc->cxcs[i], mask, 0);
}

static inline void gdsc_deassert_clamp_io(struct gdsc *sc)
{
        regmap_update_bits(sc->regmap, sc->clamp_io_ctrl,
                           GMEM_CLAMP_IO_MASK, 0);
}

static inline void gdsc_assert_clamp_io(struct gdsc *sc)
{
        regmap_update_bits(sc->regmap, sc->clamp_io_ctrl,
                           GMEM_CLAMP_IO_MASK, 1);
}

static int gdsc_enable(struct generic_pm_domain *domain)
{
        struct gdsc *sc = domain_to_gdsc(domain);
        int ret;

        if (sc->pwrsts == PWRSTS_ON)
                return gdsc_deassert_reset(sc);

        if (sc->flags & CLAMP_IO)
                gdsc_deassert_clamp_io(sc);

        ret = gdsc_toggle_logic(sc, true);
        if (ret)
                return ret;

        if (sc->pwrsts & PWRSTS_OFF)
                gdsc_force_mem_on(sc);

        /*
         * If clocks to this power domain were already on, they will take an
         * additional 4 clock cycles to re-enable after the power domain is
         * enabled. Delay to account for this. A delay is also needed to ensure
         * clocks are not enabled within 400ns of enabling power to the
         * memories.
         */
        udelay(1);

        /* Turn on HW trigger mode if supported */
        if (sc->flags & HW_CTRL) {
                ret = gdsc_hwctrl(sc, true);
                if (ret)
                        return ret;
                /*
                 * Wait for the GDSC to go through a power down and
                 * up cycle.  In case a firmware ends up polling status
                 * bits for the gdsc, it might read an 'on' status before
                 * the GDSC can finish the power cycle.
                 * We wait 1us before returning to ensure the firmware
                 * can't immediately poll the status bits.
                 */
                udelay(1);
        }

        return 0;
}

static int gdsc_disable(struct generic_pm_domain *domain)
{
        struct gdsc *sc = domain_to_gdsc(domain);
        int ret;

        if (sc->pwrsts == PWRSTS_ON)
                return gdsc_assert_reset(sc);

        /* Turn off HW trigger mode if supported */
        if (sc->flags & HW_CTRL) {
                unsigned int reg;

                ret = gdsc_hwctrl(sc, false);
                if (ret < 0)
                        return ret;
                /*
                 * Wait for the GDSC to go through a power down and
                 * up cycle.  In case we end up polling status
                 * bits for the gdsc before the power cycle is completed
                 * it might read an 'on' status wrongly.
                 */
                udelay(1);

                reg = sc->gds_hw_ctrl ? sc->gds_hw_ctrl : sc->gdscr;
                ret = gdsc_poll_status(sc, reg, true);
                if (ret)
                        return ret;
        }

        if (sc->pwrsts & PWRSTS_OFF)
                gdsc_clear_mem_on(sc);

        ret = gdsc_toggle_logic(sc, false);
        if (ret)
                return ret;

        if (sc->flags & CLAMP_IO)
                gdsc_assert_clamp_io(sc);

        return 0;
}

static int gdsc_init(struct gdsc *sc)
{
        u32 mask, val;
        int on, ret;
        unsigned int reg;

        /*
         * Disable HW trigger: collapse/restore occur based on registers writes.
         * Disable SW override: Use hardware state-machine for sequencing.
         * Configure wait time between states.
         */
        mask = HW_CONTROL_MASK | SW_OVERRIDE_MASK |
               EN_REST_WAIT_MASK | EN_FEW_WAIT_MASK | CLK_DIS_WAIT_MASK;
        val = EN_REST_WAIT_VAL | EN_FEW_WAIT_VAL | CLK_DIS_WAIT_VAL;
        ret = regmap_update_bits(sc->regmap, sc->gdscr, mask, val);
        if (ret)
                return ret;

        /* Force gdsc ON if only ON state is supported */
        if (sc->pwrsts == PWRSTS_ON) {
                ret = gdsc_toggle_logic(sc, true);
                if (ret)
                        return ret;
        }

        reg = sc->gds_hw_ctrl ? sc->gds_hw_ctrl : sc->gdscr;
        on = gdsc_is_enabled(sc, reg);
        if (on < 0)
                return on;

        /*
         * Votable GDSCs can be ON due to Vote from other masters.
         * If a Votable GDSC is ON, make sure we have a Vote.
         */
        if ((sc->flags & VOTABLE) && on)
                gdsc_enable(&sc->pd);

        if (on || (sc->pwrsts & PWRSTS_RET))
                gdsc_force_mem_on(sc);
        else
                gdsc_clear_mem_on(sc);

        sc->pd.power_off = gdsc_disable;
        sc->pd.power_on = gdsc_enable;
        pm_genpd_init(&sc->pd, NULL, !on);

        return 0;
}

int gdsc_register(struct gdsc_desc *desc,
                  struct reset_controller_dev *rcdev, struct regmap *regmap)
{
        int i, ret;
        struct genpd_onecell_data *data;
        struct device *dev = desc->dev;
        struct gdsc **scs = desc->scs;
        size_t num = desc->num;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->domains = devm_kcalloc(dev, num, sizeof(*data->domains),
                                     GFP_KERNEL);
        if (!data->domains)
                return -ENOMEM;

        data->num_domains = num;
        for (i = 0; i < num; i++) {
                if (!scs[i])
                        continue;
                scs[i]->regmap = regmap;
                scs[i]->rcdev = rcdev;
                ret = gdsc_init(scs[i]);
                if (ret)
                        return ret;
                data->domains[i] = &scs[i]->pd;
        }

        /* Add subdomains */
        for (i = 0; i < num; i++) {
                if (!scs[i])
                        continue;
                if (scs[i]->parent)
                        pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd);
        }

        return of_genpd_add_provider_onecell(dev->of_node, data);
}

void gdsc_unregister(struct gdsc_desc *desc)
{
        int i;
        struct device *dev = desc->dev;
        struct gdsc **scs = desc->scs;
        size_t num = desc->num;

        /* Remove subdomains */
        for (i = 0; i < num; i++) {
                if (!scs[i])
                        continue;
                if (scs[i]->parent)
                        pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd);
        }
        of_genpd_del_provider(dev->of_node);
}