/*
 * JZ4780 NAND/external memory controller (NEMC)
 *
 * Copyright (c) 2015 Imagination Technologies
 * Author: Alex Smith <alex@alex-smith.me.uk>
 *
 * 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.
 */

#include <linux/clk.h>
#include <linux/init.h>
#include <linux/math64.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <linux/jz4780-nemc.h>

#define NEMC_SMCRn(n)           (0x14 + (((n) - 1) * 4))
#define NEMC_NFCSR              0x50

#define NEMC_SMCR_SMT           BIT(0)
#define NEMC_SMCR_BW_SHIFT      6
#define NEMC_SMCR_BW_MASK       (0x3 << NEMC_SMCR_BW_SHIFT)
#define NEMC_SMCR_BW_8          (0 << 6)
#define NEMC_SMCR_TAS_SHIFT     8
#define NEMC_SMCR_TAS_MASK      (0xf << NEMC_SMCR_TAS_SHIFT)
#define NEMC_SMCR_TAH_SHIFT     12
#define NEMC_SMCR_TAH_MASK      (0xf << NEMC_SMCR_TAH_SHIFT)
#define NEMC_SMCR_TBP_SHIFT     16
#define NEMC_SMCR_TBP_MASK      (0xf << NEMC_SMCR_TBP_SHIFT)
#define NEMC_SMCR_TAW_SHIFT     20
#define NEMC_SMCR_TAW_MASK      (0xf << NEMC_SMCR_TAW_SHIFT)
#define NEMC_SMCR_TSTRV_SHIFT   24
#define NEMC_SMCR_TSTRV_MASK    (0x3f << NEMC_SMCR_TSTRV_SHIFT)

#define NEMC_NFCSR_NFEn(n)      BIT(((n) - 1) << 1)
#define NEMC_NFCSR_NFCEn(n)     BIT((((n) - 1) << 1) + 1)
#define NEMC_NFCSR_TNFEn(n)     BIT(16 + (n) - 1)

struct jz4780_nemc {
        spinlock_t lock;
        struct device *dev;
        void __iomem *base;
        struct clk *clk;
        uint32_t clk_period;
        unsigned long banks_present;
};

/**
 * jz4780_nemc_num_banks() - count the number of banks referenced by a device
 * @dev: device to count banks for, must be a child of the NEMC.
 *
 * Return: The number of unique NEMC banks referred to by the specified NEMC
 * child device. Unique here means that a device that references the same bank
 * multiple times in the its "reg" property will only count once.
 */
unsigned int jz4780_nemc_num_banks(struct device *dev)
{
        const __be32 *prop;
        unsigned int bank, count = 0;
        unsigned long referenced = 0;
        int i = 0;

        while ((prop = of_get_address(dev->of_node, i++, NULL, NULL))) {
                bank = of_read_number(prop, 1);
                if (!(referenced & BIT(bank))) {
                        referenced |= BIT(bank);
                        count++;
                }
        }

        return count;
}
EXPORT_SYMBOL(jz4780_nemc_num_banks);

/**
 * jz4780_nemc_set_type() - set the type of device connected to a bank
 * @dev: child device of the NEMC.
 * @bank: bank number to configure.
 * @type: type of device connected to the bank.
 */
void jz4780_nemc_set_type(struct device *dev, unsigned int bank,
                          enum jz4780_nemc_bank_type type)
{
        struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
        uint32_t nfcsr;

        nfcsr = readl(nemc->base + NEMC_NFCSR);

        /* TODO: Support toggle NAND devices. */
        switch (type) {
        case JZ4780_NEMC_BANK_SRAM:
                nfcsr &= ~(NEMC_NFCSR_TNFEn(bank) | NEMC_NFCSR_NFEn(bank));
                break;
        case JZ4780_NEMC_BANK_NAND:
                nfcsr &= ~NEMC_NFCSR_TNFEn(bank);
                nfcsr |= NEMC_NFCSR_NFEn(bank);
                break;
        }

        writel(nfcsr, nemc->base + NEMC_NFCSR);
}
EXPORT_SYMBOL(jz4780_nemc_set_type);

/**
 * jz4780_nemc_assert() - (de-)assert a NAND device's chip enable pin
 * @dev: child device of the NEMC.
 * @bank: bank number of device.
 * @assert: whether the chip enable pin should be asserted.
 *
 * (De-)asserts the chip enable pin for the NAND device connected to the
 * specified bank.
 */
void jz4780_nemc_assert(struct device *dev, unsigned int bank, bool assert)
{
        struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
        uint32_t nfcsr;

        nfcsr = readl(nemc->base + NEMC_NFCSR);

        if (assert)
                nfcsr |= NEMC_NFCSR_NFCEn(bank);
        else
                nfcsr &= ~NEMC_NFCSR_NFCEn(bank);

        writel(nfcsr, nemc->base + NEMC_NFCSR);
}
EXPORT_SYMBOL(jz4780_nemc_assert);

static uint32_t jz4780_nemc_clk_period(struct jz4780_nemc *nemc)
{
        unsigned long rate;

        rate = clk_get_rate(nemc->clk);
        if (!rate)
                return 0;

        /* Return in picoseconds. */
        return div64_ul(1000000000000ull, rate);
}

static uint32_t jz4780_nemc_ns_to_cycles(struct jz4780_nemc *nemc, uint32_t ns)
{
        return ((ns * 1000) + nemc->clk_period - 1) / nemc->clk_period;
}

static bool jz4780_nemc_configure_bank(struct jz4780_nemc *nemc,
                                       unsigned int bank,
                                       struct device_node *node)
{
        uint32_t smcr, val, cycles;

        /*
         * Conversion of tBP and tAW cycle counts to values supported by the
         * hardware (round up to the next supported value).
         */
        static const uint32_t convert_tBP_tAW[] = {
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

                /* 11 - 12 -> 12 cycles */
                11, 11,

                /* 13 - 15 -> 15 cycles */
                12, 12, 12,

                /* 16 - 20 -> 20 cycles */
                13, 13, 13, 13, 13,

                /* 21 - 25 -> 25 cycles */
                14, 14, 14, 14, 14,

                /* 26 - 31 -> 31 cycles */
                15, 15, 15, 15, 15, 15
        };

        smcr = readl(nemc->base + NEMC_SMCRn(bank));
        smcr &= ~NEMC_SMCR_SMT;

        if (!of_property_read_u32(node, "ingenic,nemc-bus-width", &val)) {
                smcr &= ~NEMC_SMCR_BW_MASK;
                switch (val) {
                case 8:
                        smcr |= NEMC_SMCR_BW_8;
                        break;
                default:
                        /*
                         * Earlier SoCs support a 16 bit bus width (the 4780
                         * does not), until those are properly supported, error.
                         */
                        dev_err(nemc->dev, "unsupported bus width: %u\n", val);
                        return false;
                }
        }

        if (of_property_read_u32(node, "ingenic,nemc-tAS", &val) == 0) {
                smcr &= ~NEMC_SMCR_TAS_MASK;
                cycles = jz4780_nemc_ns_to_cycles(nemc, val);
                if (cycles > 15) {
                        dev_err(nemc->dev, "tAS %u is too high (%u cycles)\n",
                                val, cycles);
                        return false;
                }

                smcr |= cycles << NEMC_SMCR_TAS_SHIFT;
        }

        if (of_property_read_u32(node, "ingenic,nemc-tAH", &val) == 0) {
                smcr &= ~NEMC_SMCR_TAH_MASK;
                cycles = jz4780_nemc_ns_to_cycles(nemc, val);
                if (cycles > 15) {
                        dev_err(nemc->dev, "tAH %u is too high (%u cycles)\n",
                                val, cycles);
                        return false;
                }

                smcr |= cycles << NEMC_SMCR_TAH_SHIFT;
        }

        if (of_property_read_u32(node, "ingenic,nemc-tBP", &val) == 0) {
                smcr &= ~NEMC_SMCR_TBP_MASK;
                cycles = jz4780_nemc_ns_to_cycles(nemc, val);
                if (cycles > 31) {
                        dev_err(nemc->dev, "tBP %u is too high (%u cycles)\n",
                                val, cycles);
                        return false;
                }

                smcr |= convert_tBP_tAW[cycles] << NEMC_SMCR_TBP_SHIFT;
        }

        if (of_property_read_u32(node, "ingenic,nemc-tAW", &val) == 0) {
                smcr &= ~NEMC_SMCR_TAW_MASK;
                cycles = jz4780_nemc_ns_to_cycles(nemc, val);
                if (cycles > 31) {
                        dev_err(nemc->dev, "tAW %u is too high (%u cycles)\n",
                                val, cycles);
                        return false;
                }

                smcr |= convert_tBP_tAW[cycles] << NEMC_SMCR_TAW_SHIFT;
        }

        if (of_property_read_u32(node, "ingenic,nemc-tSTRV", &val) == 0) {
                smcr &= ~NEMC_SMCR_TSTRV_MASK;
                cycles = jz4780_nemc_ns_to_cycles(nemc, val);
                if (cycles > 63) {
                        dev_err(nemc->dev, "tSTRV %u is too high (%u cycles)\n",
                                val, cycles);
                        return false;
                }

                smcr |= cycles << NEMC_SMCR_TSTRV_SHIFT;
        }

        writel(smcr, nemc->base + NEMC_SMCRn(bank));
        return true;
}

static int jz4780_nemc_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct jz4780_nemc *nemc;
        struct resource *res;
        struct device_node *child;
        const __be32 *prop;
        unsigned int bank;
        unsigned long referenced;
        int i, ret;

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

        spin_lock_init(&nemc->lock);
        nemc->dev = dev;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        nemc->base = devm_ioremap_resource(dev, res);
        if (IS_ERR(nemc->base)) {
                dev_err(dev, "failed to get I/O memory\n");
                return PTR_ERR(nemc->base);
        }

        writel(0, nemc->base + NEMC_NFCSR);

        nemc->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(nemc->clk)) {
                dev_err(dev, "failed to get clock\n");
                return PTR_ERR(nemc->clk);
        }

        ret = clk_prepare_enable(nemc->clk);
        if (ret) {
                dev_err(dev, "failed to enable clock: %d\n", ret);
                return ret;
        }

        nemc->clk_period = jz4780_nemc_clk_period(nemc);
        if (!nemc->clk_period) {
                dev_err(dev, "failed to calculate clock period\n");
                clk_disable_unprepare(nemc->clk);
                return -EINVAL;
        }

        /*
         * Iterate over child devices, check that they do not conflict with
         * each other, and register child devices for them. If a child device
         * has invalid properties, it is ignored and no platform device is
         * registered for it.
         */
        for_each_child_of_node(nemc->dev->of_node, child) {
                referenced = 0;
                i = 0;
                while ((prop = of_get_address(child, i++, NULL, NULL))) {
                        bank = of_read_number(prop, 1);
                        if (bank < 1 || bank >= JZ4780_NEMC_NUM_BANKS) {
                                dev_err(nemc->dev,
                                        "%pOF requests invalid bank %u\n",
                                        child, bank);

                                /* Will continue the outer loop below. */
                                referenced = 0;
                                break;
                        }

                        referenced |= BIT(bank);
                }

                if (!referenced) {
                        dev_err(nemc->dev, "%pOF has no addresses\n",
                                child);
                        continue;
                } else if (nemc->banks_present & referenced) {
                        dev_err(nemc->dev, "%pOF conflicts with another node\n",
                                child);
                        continue;
                }

                /* Configure bank parameters. */
                for_each_set_bit(bank, &referenced, JZ4780_NEMC_NUM_BANKS) {
                        if (!jz4780_nemc_configure_bank(nemc, bank, child)) {
                                referenced = 0;
                                break;
                        }
                }

                if (referenced) {
                        if (of_platform_device_create(child, NULL, nemc->dev))
                                nemc->banks_present |= referenced;
                }
        }

        platform_set_drvdata(pdev, nemc);
        dev_info(dev, "JZ4780 NEMC initialised\n");
        return 0;
}

static int jz4780_nemc_remove(struct platform_device *pdev)
{
        struct jz4780_nemc *nemc = platform_get_drvdata(pdev);

        clk_disable_unprepare(nemc->clk);
        return 0;
}

static const struct of_device_id jz4780_nemc_dt_match[] = {
        { .compatible = "ingenic,jz4780-nemc" },
        {},
};

static struct platform_driver jz4780_nemc_driver = {
        .probe          = jz4780_nemc_probe,
        .remove         = jz4780_nemc_remove,
        .driver = {
                .name   = "jz4780-nemc",
                .of_match_table = of_match_ptr(jz4780_nemc_dt_match),
        },
};

static int __init jz4780_nemc_init(void)
{
        return platform_driver_register(&jz4780_nemc_driver);
}
subsys_initcall(jz4780_nemc_init);