// SPDX-License-Identifier: GPL-2.0+
/*
 * SPI driver for Renesas Synchronization Management Unit (SMU) devices.
 *
 * Copyright (C) 2021 Integrated Device Technology, Inc., a Renesas Company.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mfd/core.h>
#include <linux/mfd/rsmu.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/regmap.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>

#include "rsmu.h"

#define RSMU_CM_PAGE_ADDR               0x7C
#define RSMU_SABRE_PAGE_ADDR            0x7F
#define RSMU_PAGE_MASK                  0xFFFFFF80
#define RSMU_ADDR_MASK                  0x7F

static int rsmu_read_device(struct rsmu_ddata *rsmu, u8 reg, u8 *buf, u16 bytes)
{
        struct spi_device *client = to_spi_device(rsmu->dev);
        struct spi_transfer xfer = {0};
        struct spi_message msg;
        u8 cmd[RSMU_MAX_READ_COUNT + 1] = {0};
        u8 rsp[RSMU_MAX_READ_COUNT + 1] = {0};
        int ret;

        if (bytes > RSMU_MAX_READ_COUNT)
                return -EINVAL;

        cmd[0] = reg | 0x80;
        xfer.rx_buf = rsp;
        xfer.len = bytes + 1;
        xfer.tx_buf = cmd;
        xfer.bits_per_word = client->bits_per_word;
        xfer.speed_hz = client->max_speed_hz;

        spi_message_init(&msg);
        spi_message_add_tail(&xfer, &msg);

        /*
         * 4-wire SPI is a shift register, so for every byte you send,
         * you get one back at the same time. Example read from 0xC024,
         * which has value of 0x2D
         *
         * MOSI:
         *       7C 00 C0 #Set page register
         *       A4 00    #MSB is set, so this is read command
         * MISO:
         *       XX 2D    #XX is a dummy byte from sending A4 and we
         *                 need to throw it away
         */
        ret = spi_sync(client, &msg);
        if (ret >= 0)
                memcpy(buf, &rsp[1], xfer.len-1);

        return ret;
}

static int rsmu_write_device(struct rsmu_ddata *rsmu, u8 reg, u8 *buf, u16 bytes)
{
        struct spi_device *client = to_spi_device(rsmu->dev);
        struct spi_transfer xfer = {0};
        struct spi_message msg;
        u8 cmd[RSMU_MAX_WRITE_COUNT + 1] = {0};

        if (bytes > RSMU_MAX_WRITE_COUNT)
                return -EINVAL;

        cmd[0] = reg;
        memcpy(&cmd[1], buf, bytes);

        xfer.len = bytes + 1;
        xfer.tx_buf = cmd;
        xfer.bits_per_word = client->bits_per_word;
        xfer.speed_hz = client->max_speed_hz;
        spi_message_init(&msg);
        spi_message_add_tail(&xfer, &msg);

        return  spi_sync(client, &msg);
}

/*
 * 1-byte (1B) offset addressing:
 * 16-bit register address: the lower 7 bits of the register address come
 * from the offset addr byte and the upper 9 bits come from the page register.
 */
static int rsmu_write_page_register(struct rsmu_ddata *rsmu, u32 reg)
{
        u8 page_reg;
        u8 buf[4];
        u16 bytes;
        u32 page;
        int err;

        switch (rsmu->type) {
        case RSMU_CM:
                page_reg = RSMU_CM_PAGE_ADDR;
                page = (reg | RSMU_CM_SCSR_BASE) & RSMU_PAGE_MASK;
                buf[0] = (u8)(page & 0xFF);
                buf[1] = (u8)((page >> 8) & 0xFF);
                buf[2] = (u8)((page >> 16) & 0xFF);
                buf[3] = (u8)((page >> 24) & 0xFF);
                bytes = 4;
                break;
        case RSMU_SABRE:
                /* Do not modify page register if reg is page register itself */
                if ((reg & RSMU_ADDR_MASK) == RSMU_ADDR_MASK)
                        return 0;
                page_reg = RSMU_SABRE_PAGE_ADDR;
                page = reg & RSMU_PAGE_MASK;
                /* The three page bits are located in the single Page Register */
                buf[0] = (u8)((page >> 7) & 0x7);
                bytes = 1;
                break;
        default:
                dev_err(rsmu->dev, "Unsupported RSMU device type: %d\n", rsmu->type);
                return -ENODEV;
        }

        /* Simply return if we are on the same page */
        if (rsmu->page == page)
                return 0;

        err = rsmu_write_device(rsmu, page_reg, buf, bytes);
        if (err)
                dev_err(rsmu->dev, "Failed to set page offset 0x%x\n", page);
        else
                /* Remember the last page */
                rsmu->page = page;

        return err;
}

static int rsmu_reg_read(void *context, unsigned int reg, unsigned int *val)
{
        struct rsmu_ddata *rsmu = spi_get_drvdata((struct spi_device *)context);
        u8 addr = (u8)(reg & RSMU_ADDR_MASK);
        int err;

        err = rsmu_write_page_register(rsmu, reg);
        if (err)
                return err;

        err = rsmu_read_device(rsmu, addr, (u8 *)val, 1);
        if (err)
                dev_err(rsmu->dev, "Failed to read offset address 0x%x\n", addr);

        return err;
}

static int rsmu_reg_write(void *context, unsigned int reg, unsigned int val)
{
        struct rsmu_ddata *rsmu = spi_get_drvdata((struct spi_device *)context);
        u8 addr = (u8)(reg & RSMU_ADDR_MASK);
        u8 data = (u8)val;
        int err;

        err = rsmu_write_page_register(rsmu, reg);
        if (err)
                return err;

        err = rsmu_write_device(rsmu, addr, &data, 1);
        if (err)
                dev_err(rsmu->dev,
                        "Failed to write offset address 0x%x\n", addr);

        return err;
}

static const struct regmap_config rsmu_cm_regmap_config = {
        .reg_bits = 32,
        .val_bits = 8,
        .max_register = 0x20120000,
        .reg_read = rsmu_reg_read,
        .reg_write = rsmu_reg_write,
        .cache_type = REGCACHE_NONE,
};

static const struct regmap_config rsmu_sabre_regmap_config = {
        .reg_bits = 16,
        .val_bits = 8,
        .max_register = 0x400,
        .reg_read = rsmu_reg_read,
        .reg_write = rsmu_reg_write,
        .cache_type = REGCACHE_NONE,
};

static int rsmu_spi_probe(struct spi_device *client)
{
        const struct spi_device_id *id = spi_get_device_id(client);
        const struct regmap_config *cfg;
        struct rsmu_ddata *rsmu;
        int ret;

        rsmu = devm_kzalloc(&client->dev, sizeof(*rsmu), GFP_KERNEL);
        if (!rsmu)
                return -ENOMEM;

        spi_set_drvdata(client, rsmu);

        rsmu->dev = &client->dev;
        rsmu->type = (enum rsmu_type)id->driver_data;

        /* Initialize regmap */
        switch (rsmu->type) {
        case RSMU_CM:
                cfg = &rsmu_cm_regmap_config;
                break;
        case RSMU_SABRE:
                cfg = &rsmu_sabre_regmap_config;
                break;
        default:
                dev_err(rsmu->dev, "Unsupported RSMU device type: %d\n", rsmu->type);
                return -ENODEV;
        }

        rsmu->regmap = devm_regmap_init(&client->dev, NULL, client, cfg);
        if (IS_ERR(rsmu->regmap)) {
                ret = PTR_ERR(rsmu->regmap);
                dev_err(rsmu->dev, "Failed to allocate register map: %d\n", ret);
                return ret;
        }

        return rsmu_core_init(rsmu);
}

static void rsmu_spi_remove(struct spi_device *client)
{
        struct rsmu_ddata *rsmu = spi_get_drvdata(client);

        rsmu_core_exit(rsmu);
}

static const struct spi_device_id rsmu_spi_id[] = {
        { "8a34000",  RSMU_CM },
        { "8a34001",  RSMU_CM },
        { "8a34002",  RSMU_CM },
        { "82p33810", RSMU_SABRE },
        { "82p33811", RSMU_SABRE },
        {}
};
MODULE_DEVICE_TABLE(spi, rsmu_spi_id);

static const struct of_device_id rsmu_spi_of_match[] = {
        { .compatible = "idt,8a34000",  .data = (void *)RSMU_CM },
        { .compatible = "idt,8a34001",  .data = (void *)RSMU_CM },
        { .compatible = "idt,8a34002",  .data = (void *)RSMU_CM },
        { .compatible = "idt,82p33810", .data = (void *)RSMU_SABRE },
        { .compatible = "idt,82p33811", .data = (void *)RSMU_SABRE },
        {}
};
MODULE_DEVICE_TABLE(of, rsmu_spi_of_match);

static struct spi_driver rsmu_spi_driver = {
        .driver = {
                .name = "rsmu-spi",
                .of_match_table = rsmu_spi_of_match,
        },
        .probe = rsmu_spi_probe,
        .remove = rsmu_spi_remove,
        .id_table = rsmu_spi_id,
};

static int __init rsmu_spi_init(void)
{
        return spi_register_driver(&rsmu_spi_driver);
}
subsys_initcall(rsmu_spi_init);

static void __exit rsmu_spi_exit(void)
{
        spi_unregister_driver(&rsmu_spi_driver);
}
module_exit(rsmu_spi_exit);

MODULE_DESCRIPTION("Renesas SMU SPI driver");
MODULE_LICENSE("GPL");