// SPDX-License-Identifier: GPL-2.0-only
/*
 * RSB (Reduced Serial Bus) driver.
 *
 * Author: Chen-Yu Tsai <wens@csie.org>
 *
 * The RSB controller looks like an SMBus controller which only supports
 * byte and word data transfers. But, it differs from standard SMBus
 * protocol on several aspects:
 * - it uses addresses set at runtime to address slaves. Runtime addresses
 *   are sent to slaves using their 12bit hardware addresses. Up to 15
 *   runtime addresses are available.
 * - it adds a parity bit every 8bits of data and address for read and
 *   write accesses; this replaces the ack bit
 * - only one read access is required to read a byte (instead of a write
 *   followed by a read access in standard SMBus protocol)
 * - there's no Ack bit after each read access
 *
 * This means this bus cannot be used to interface with standard SMBus
 * devices. Devices known to support this interface include the AXP223,
 * AXP809, and AXP806 PMICs, and the AC100 audio codec, all from X-Powers.
 *
 * A description of the operation and wire protocol can be found in the
 * RSB section of Allwinner's A80 user manual, which can be found at
 *
 *     https://github.com/allwinner-zh/documents/tree/master/A80
 *
 * This document is officially released by Allwinner.
 *
 * This driver is based on i2c-sun6i-p2wi.c, the P2WI bus driver.
 */

#include <linux/clk.h>
#include <linux/clk/clk-conf.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/reset.h>
#include <linux/slab.h>
#include <linux/sunxi-rsb.h>
#include <linux/types.h>

/* RSB registers */
#define RSB_CTRL        0x0     /* Global control */
#define RSB_CCR         0x4     /* Clock control */
#define RSB_INTE        0x8     /* Interrupt controls */
#define RSB_INTS        0xc     /* Interrupt status */
#define RSB_ADDR        0x10    /* Address to send with read/write command */
#define RSB_DATA        0x1c    /* Data to read/write */
#define RSB_LCR         0x24    /* Line control */
#define RSB_DMCR        0x28    /* Device mode (init) control */
#define RSB_CMD         0x2c    /* RSB Command */
#define RSB_DAR         0x30    /* Device address / runtime address */

/* CTRL fields */
#define RSB_CTRL_START_TRANS            BIT(7)
#define RSB_CTRL_ABORT_TRANS            BIT(6)
#define RSB_CTRL_GLOBAL_INT_ENB         BIT(1)
#define RSB_CTRL_SOFT_RST               BIT(0)

/* CLK CTRL fields */
#define RSB_CCR_SDA_OUT_DELAY(v)        (((v) & 0x7) << 8)
#define RSB_CCR_MAX_CLK_DIV             0xff
#define RSB_CCR_CLK_DIV(v)              ((v) & RSB_CCR_MAX_CLK_DIV)

/* STATUS fields */
#define RSB_INTS_TRANS_ERR_ACK          BIT(16)
#define RSB_INTS_TRANS_ERR_DATA_BIT(v)  (((v) >> 8) & 0xf)
#define RSB_INTS_TRANS_ERR_DATA         GENMASK(11, 8)
#define RSB_INTS_LOAD_BSY               BIT(2)
#define RSB_INTS_TRANS_ERR              BIT(1)
#define RSB_INTS_TRANS_OVER             BIT(0)

/* LINE CTRL fields*/
#define RSB_LCR_SCL_STATE               BIT(5)
#define RSB_LCR_SDA_STATE               BIT(4)
#define RSB_LCR_SCL_CTL                 BIT(3)
#define RSB_LCR_SCL_CTL_EN              BIT(2)
#define RSB_LCR_SDA_CTL                 BIT(1)
#define RSB_LCR_SDA_CTL_EN              BIT(0)

/* DEVICE MODE CTRL field values */
#define RSB_DMCR_DEVICE_START           BIT(31)
#define RSB_DMCR_MODE_DATA              (0x7c << 16)
#define RSB_DMCR_MODE_REG               (0x3e << 8)
#define RSB_DMCR_DEV_ADDR               0x00

/* CMD values */
#define RSB_CMD_RD8                     0x8b
#define RSB_CMD_RD16                    0x9c
#define RSB_CMD_RD32                    0xa6
#define RSB_CMD_WR8                     0x4e
#define RSB_CMD_WR16                    0x59
#define RSB_CMD_WR32                    0x63
#define RSB_CMD_STRA                    0xe8

/* DAR fields */
#define RSB_DAR_RTA(v)                  (((v) & 0xff) << 16)
#define RSB_DAR_DA(v)                   ((v) & 0xffff)

#define RSB_MAX_FREQ                    20000000

#define RSB_CTRL_NAME                   "sunxi-rsb"

struct sunxi_rsb_addr_map {
        u16 hwaddr;
        u8 rtaddr;
};

struct sunxi_rsb {
        struct device *dev;
        void __iomem *regs;
        struct clk *clk;
        struct reset_control *rstc;
        struct completion complete;
        struct mutex lock;
        unsigned int status;
        u32 clk_freq;
};

/* bus / slave device related functions */
static const struct bus_type sunxi_rsb_bus;

static int sunxi_rsb_device_match(struct device *dev, const struct device_driver *drv)
{
        return of_driver_match_device(dev, drv);
}

static int sunxi_rsb_device_probe(struct device *dev)
{
        const struct sunxi_rsb_driver *drv = to_sunxi_rsb_driver(dev->driver);
        struct sunxi_rsb_device *rdev = to_sunxi_rsb_device(dev);
        int ret;

        if (!drv->probe)
                return -ENODEV;

        if (!rdev->irq) {
                int irq = -ENOENT;

                if (dev->of_node)
                        irq = of_irq_get(dev->of_node, 0);

                if (irq == -EPROBE_DEFER)
                        return irq;
                if (irq < 0)
                        irq = 0;

                rdev->irq = irq;
        }

        ret = of_clk_set_defaults(dev->of_node, false);
        if (ret < 0)
                return ret;

        return drv->probe(rdev);
}

static void sunxi_rsb_device_remove(struct device *dev)
{
        const struct sunxi_rsb_driver *drv = to_sunxi_rsb_driver(dev->driver);

        drv->remove(to_sunxi_rsb_device(dev));
}

static int sunxi_rsb_device_modalias(const struct device *dev, struct kobj_uevent_env *env)
{
        return of_device_uevent_modalias(dev, env);
}

static const struct bus_type sunxi_rsb_bus = {
        .name           = RSB_CTRL_NAME,
        .match          = sunxi_rsb_device_match,
        .probe          = sunxi_rsb_device_probe,
        .remove         = sunxi_rsb_device_remove,
        .uevent         = sunxi_rsb_device_modalias,
};

static void sunxi_rsb_dev_release(struct device *dev)
{
        struct sunxi_rsb_device *rdev = to_sunxi_rsb_device(dev);

        kfree(rdev);
}

/**
 * sunxi_rsb_device_create() - allocate and add an RSB device
 * @rsb:        RSB controller
 * @node:       RSB slave device node
 * @hwaddr:     RSB slave hardware address
 * @rtaddr:     RSB slave runtime address
 */
static struct sunxi_rsb_device *sunxi_rsb_device_create(struct sunxi_rsb *rsb,
                struct device_node *node, u16 hwaddr, u8 rtaddr)
{
        int err;
        struct sunxi_rsb_device *rdev;

        rdev = kzalloc_obj(*rdev);
        if (!rdev)
                return ERR_PTR(-ENOMEM);

        rdev->rsb = rsb;
        rdev->hwaddr = hwaddr;
        rdev->rtaddr = rtaddr;
        rdev->dev.bus = &sunxi_rsb_bus;
        rdev->dev.parent = rsb->dev;
        rdev->dev.of_node = node;
        rdev->dev.release = sunxi_rsb_dev_release;

        dev_set_name(&rdev->dev, "%s-%x", RSB_CTRL_NAME, hwaddr);

        err = device_register(&rdev->dev);
        if (err < 0) {
                dev_err(&rdev->dev, "Can't add %s, status %d\n",
                        dev_name(&rdev->dev), err);
                goto err_device_add;
        }

        dev_dbg(&rdev->dev, "device %s registered\n", dev_name(&rdev->dev));

        return rdev;

err_device_add:
        put_device(&rdev->dev);

        return ERR_PTR(err);
}

/**
 * sunxi_rsb_device_unregister(): unregister an RSB device
 * @rdev:       rsb_device to be removed
 */
static void sunxi_rsb_device_unregister(struct sunxi_rsb_device *rdev)
{
        device_unregister(&rdev->dev);
}

static int sunxi_rsb_remove_devices(struct device *dev, void *data)
{
        struct sunxi_rsb_device *rdev = to_sunxi_rsb_device(dev);

        if (dev->bus == &sunxi_rsb_bus)
                sunxi_rsb_device_unregister(rdev);

        return 0;
}

/**
 * sunxi_rsb_driver_register() - Register device driver with RSB core
 * @rdrv:       device driver to be associated with slave-device.
 *
 * This API will register the client driver with the RSB framework.
 * It is typically called from the driver's module-init function.
 */
int sunxi_rsb_driver_register(struct sunxi_rsb_driver *rdrv)
{
        rdrv->driver.bus = &sunxi_rsb_bus;
        return driver_register(&rdrv->driver);
}
EXPORT_SYMBOL_GPL(sunxi_rsb_driver_register);

/* common code that starts a transfer */
static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
{
        u32 int_mask, status;
        bool timeout;

        if (readl(rsb->regs + RSB_CTRL) & RSB_CTRL_START_TRANS) {
                dev_dbg(rsb->dev, "RSB transfer still in progress\n");
                return -EBUSY;
        }

        reinit_completion(&rsb->complete);

        int_mask = RSB_INTS_LOAD_BSY | RSB_INTS_TRANS_ERR | RSB_INTS_TRANS_OVER;
        writel(int_mask, rsb->regs + RSB_INTE);
        writel(RSB_CTRL_START_TRANS | RSB_CTRL_GLOBAL_INT_ENB,
               rsb->regs + RSB_CTRL);

        if (irqs_disabled()) {
                timeout = readl_poll_timeout_atomic(rsb->regs + RSB_INTS,
                                                    status, (status & int_mask),
                                                    10, 100000);
                writel(status, rsb->regs + RSB_INTS);
        } else {
                timeout = !wait_for_completion_io_timeout(&rsb->complete,
                                                          msecs_to_jiffies(100));
                status = rsb->status;
        }

        if (timeout) {
                dev_dbg(rsb->dev, "RSB timeout\n");

                /* abort the transfer */
                writel(RSB_CTRL_ABORT_TRANS, rsb->regs + RSB_CTRL);

                /* clear any interrupt flags */
                writel(readl(rsb->regs + RSB_INTS), rsb->regs + RSB_INTS);

                return -ETIMEDOUT;
        }

        if (status & RSB_INTS_LOAD_BSY) {
                dev_dbg(rsb->dev, "RSB busy\n");
                return -EBUSY;
        }

        if (status & RSB_INTS_TRANS_ERR) {
                if (status & RSB_INTS_TRANS_ERR_ACK) {
                        dev_dbg(rsb->dev, "RSB slave nack\n");
                        return -EINVAL;
                }

                if (status & RSB_INTS_TRANS_ERR_DATA) {
                        dev_dbg(rsb->dev, "RSB transfer data error\n");
                        return -EIO;
                }
        }

        return 0;
}

static int sunxi_rsb_read(struct sunxi_rsb *rsb, u8 rtaddr, u8 addr,
                          u32 *buf, size_t len)
{
        u32 cmd;
        int ret;

        if (!buf)
                return -EINVAL;

        switch (len) {
        case 1:
                cmd = RSB_CMD_RD8;
                break;
        case 2:
                cmd = RSB_CMD_RD16;
                break;
        case 4:
                cmd = RSB_CMD_RD32;
                break;
        default:
                dev_err(rsb->dev, "Invalid access width: %zd\n", len);
                return -EINVAL;
        }

        ret = pm_runtime_resume_and_get(rsb->dev);
        if (ret)
                return ret;

        mutex_lock(&rsb->lock);

        writel(addr, rsb->regs + RSB_ADDR);
        writel(RSB_DAR_RTA(rtaddr), rsb->regs + RSB_DAR);
        writel(cmd, rsb->regs + RSB_CMD);

        ret = _sunxi_rsb_run_xfer(rsb);
        if (ret)
                goto unlock;

        *buf = readl(rsb->regs + RSB_DATA) & GENMASK(len * 8 - 1, 0);

unlock:
        mutex_unlock(&rsb->lock);

        pm_runtime_put_autosuspend(rsb->dev);

        return ret;
}

static int sunxi_rsb_write(struct sunxi_rsb *rsb, u8 rtaddr, u8 addr,
                           const u32 *buf, size_t len)
{
        u32 cmd;
        int ret;

        if (!buf)
                return -EINVAL;

        switch (len) {
        case 1:
                cmd = RSB_CMD_WR8;
                break;
        case 2:
                cmd = RSB_CMD_WR16;
                break;
        case 4:
                cmd = RSB_CMD_WR32;
                break;
        default:
                dev_err(rsb->dev, "Invalid access width: %zd\n", len);
                return -EINVAL;
        }

        ret = pm_runtime_resume_and_get(rsb->dev);
        if (ret)
                return ret;

        mutex_lock(&rsb->lock);

        writel(addr, rsb->regs + RSB_ADDR);
        writel(RSB_DAR_RTA(rtaddr), rsb->regs + RSB_DAR);
        writel(*buf, rsb->regs + RSB_DATA);
        writel(cmd, rsb->regs + RSB_CMD);
        ret = _sunxi_rsb_run_xfer(rsb);

        mutex_unlock(&rsb->lock);

        pm_runtime_put_autosuspend(rsb->dev);

        return ret;
}

/* RSB regmap functions */
struct sunxi_rsb_ctx {
        struct sunxi_rsb_device *rdev;
        int size;
};

static int regmap_sunxi_rsb_reg_read(void *context, unsigned int reg,
                                     unsigned int *val)
{
        struct sunxi_rsb_ctx *ctx = context;
        struct sunxi_rsb_device *rdev = ctx->rdev;

        if (reg > 0xff)
                return -EINVAL;

        return sunxi_rsb_read(rdev->rsb, rdev->rtaddr, reg, val, ctx->size);
}

static int regmap_sunxi_rsb_reg_write(void *context, unsigned int reg,
                                      unsigned int val)
{
        struct sunxi_rsb_ctx *ctx = context;
        struct sunxi_rsb_device *rdev = ctx->rdev;

        return sunxi_rsb_write(rdev->rsb, rdev->rtaddr, reg, &val, ctx->size);
}

static void regmap_sunxi_rsb_free_ctx(void *context)
{
        struct sunxi_rsb_ctx *ctx = context;

        kfree(ctx);
}

static const struct regmap_bus regmap_sunxi_rsb = {
        .reg_write = regmap_sunxi_rsb_reg_write,
        .reg_read = regmap_sunxi_rsb_reg_read,
        .free_context = regmap_sunxi_rsb_free_ctx,
        .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
        .val_format_endian_default = REGMAP_ENDIAN_NATIVE,
};

static struct sunxi_rsb_ctx *regmap_sunxi_rsb_init_ctx(struct sunxi_rsb_device *rdev,
                const struct regmap_config *config)
{
        struct sunxi_rsb_ctx *ctx;

        switch (config->val_bits) {
        case 8:
        case 16:
        case 32:
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        ctx = kzalloc_obj(*ctx);
        if (!ctx)
                return ERR_PTR(-ENOMEM);

        ctx->rdev = rdev;
        ctx->size = config->val_bits / 8;

        return ctx;
}

struct regmap *__devm_regmap_init_sunxi_rsb(struct sunxi_rsb_device *rdev,
                                            const struct regmap_config *config,
                                            struct lock_class_key *lock_key,
                                            const char *lock_name)
{
        struct sunxi_rsb_ctx *ctx = regmap_sunxi_rsb_init_ctx(rdev, config);

        if (IS_ERR(ctx))
                return ERR_CAST(ctx);

        return __devm_regmap_init(&rdev->dev, &regmap_sunxi_rsb, ctx, config,
                                  lock_key, lock_name);
}
EXPORT_SYMBOL_GPL(__devm_regmap_init_sunxi_rsb);

/* RSB controller driver functions */
static irqreturn_t sunxi_rsb_irq(int irq, void *dev_id)
{
        struct sunxi_rsb *rsb = dev_id;
        u32 status;

        status = readl(rsb->regs + RSB_INTS);
        rsb->status = status;

        /* Clear interrupts */
        status &= (RSB_INTS_LOAD_BSY | RSB_INTS_TRANS_ERR |
                   RSB_INTS_TRANS_OVER);
        writel(status, rsb->regs + RSB_INTS);

        complete(&rsb->complete);

        return IRQ_HANDLED;
}

static int sunxi_rsb_init_device_mode(struct sunxi_rsb *rsb)
{
        int ret = 0;
        u32 reg;

        /* send init sequence */
        writel(RSB_DMCR_DEVICE_START | RSB_DMCR_MODE_DATA |
               RSB_DMCR_MODE_REG | RSB_DMCR_DEV_ADDR, rsb->regs + RSB_DMCR);

        readl_poll_timeout(rsb->regs + RSB_DMCR, reg,
                           !(reg & RSB_DMCR_DEVICE_START), 100, 250000);
        if (reg & RSB_DMCR_DEVICE_START)
                ret = -ETIMEDOUT;

        /* clear interrupt status bits */
        writel(readl(rsb->regs + RSB_INTS), rsb->regs + RSB_INTS);

        return ret;
}

/*
 * There are 15 valid runtime addresses, though Allwinner typically
 * skips the first, for unknown reasons, and uses the following three.
 *
 * 0x17, 0x2d, 0x3a, 0x4e, 0x59, 0x63, 0x74, 0x8b,
 * 0x9c, 0xa6, 0xb1, 0xc5, 0xd2, 0xe8, 0xff
 *
 * No designs with 2 RSB slave devices sharing identical hardware
 * addresses on the same bus have been seen in the wild. All designs
 * use 0x2d for the primary PMIC, 0x3a for the secondary PMIC if
 * there is one, and 0x45 for peripheral ICs.
 *
 * The hardware does not seem to support re-setting runtime addresses.
 * Attempts to do so result in the slave devices returning a NACK.
 * Hence we just hardcode the mapping here, like Allwinner does.
 */

static const struct sunxi_rsb_addr_map sunxi_rsb_addr_maps[] = {
        { 0x3a3, 0x2d }, /* Primary PMIC: AXP223, AXP809, AXP81X, ... */
        { 0x745, 0x3a }, /* Secondary PMIC: AXP806, ... */
        { 0xe89, 0x4e }, /* Peripheral IC: AC100, ... */
};

static u8 sunxi_rsb_get_rtaddr(u16 hwaddr)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(sunxi_rsb_addr_maps); i++)
                if (hwaddr == sunxi_rsb_addr_maps[i].hwaddr)
                        return sunxi_rsb_addr_maps[i].rtaddr;

        return 0; /* 0 is an invalid runtime address */
}

static int of_rsb_register_devices(struct sunxi_rsb *rsb)
{
        struct device *dev = rsb->dev;
        struct device_node *child, *np = dev->of_node;
        u32 hwaddr;
        u8 rtaddr;
        int ret;

        if (!np)
                return -EINVAL;

        /* Runtime addresses for all slaves should be set first */
        for_each_available_child_of_node(np, child) {
                dev_dbg(dev, "setting child %pOF runtime address\n",
                        child);

                ret = of_property_read_u32(child, "reg", &hwaddr);
                if (ret) {
                        dev_err(dev, "%pOF: invalid 'reg' property: %d\n",
                                child, ret);
                        continue;
                }

                rtaddr = sunxi_rsb_get_rtaddr(hwaddr);
                if (!rtaddr) {
                        dev_err(dev, "%pOF: unknown hardware device address\n",
                                child);
                        continue;
                }

                /*
                 * Since no devices have been registered yet, we are the
                 * only ones using the bus, we can skip locking the bus.
                 */

                /* setup command parameters */
                writel(RSB_CMD_STRA, rsb->regs + RSB_CMD);
                writel(RSB_DAR_RTA(rtaddr) | RSB_DAR_DA(hwaddr),
                       rsb->regs + RSB_DAR);

                /* send command */
                ret = _sunxi_rsb_run_xfer(rsb);
                if (ret)
                        dev_warn(dev, "%pOF: set runtime address failed: %d\n",
                                 child, ret);
        }

        /* Then we start adding devices and probing them */
        for_each_available_child_of_node(np, child) {
                struct sunxi_rsb_device *rdev;

                dev_dbg(dev, "adding child %pOF\n", child);

                ret = of_property_read_u32(child, "reg", &hwaddr);
                if (ret)
                        continue;

                rtaddr = sunxi_rsb_get_rtaddr(hwaddr);
                if (!rtaddr)
                        continue;

                rdev = sunxi_rsb_device_create(rsb, child, hwaddr, rtaddr);
                if (IS_ERR(rdev))
                        dev_err(dev, "failed to add child device %pOF: %ld\n",
                                child, PTR_ERR(rdev));
        }

        return 0;
}

static int sunxi_rsb_hw_init(struct sunxi_rsb *rsb)
{
        struct device *dev = rsb->dev;
        unsigned long p_clk_freq;
        u32 clk_delay, reg;
        int clk_div, ret;

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

        ret = reset_control_deassert(rsb->rstc);
        if (ret) {
                dev_err(dev, "failed to deassert reset line: %d\n", ret);
                goto err_clk_disable;
        }

        /* reset the controller */
        writel(RSB_CTRL_SOFT_RST, rsb->regs + RSB_CTRL);
        readl_poll_timeout(rsb->regs + RSB_CTRL, reg,
                           !(reg & RSB_CTRL_SOFT_RST), 1000, 100000);

        /*
         * Clock frequency and delay calculation code is from
         * Allwinner U-boot sources.
         *
         * From A83 user manual:
         * bus clock frequency = parent clock frequency / (2 * (divider + 1))
         */
        p_clk_freq = clk_get_rate(rsb->clk);
        clk_div = p_clk_freq / rsb->clk_freq / 2;
        if (!clk_div)
                clk_div = 1;
        else if (clk_div > RSB_CCR_MAX_CLK_DIV + 1)
                clk_div = RSB_CCR_MAX_CLK_DIV + 1;

        clk_delay = clk_div >> 1;
        if (!clk_delay)
                clk_delay = 1;

        dev_info(dev, "RSB running at %lu Hz\n", p_clk_freq / clk_div / 2);
        writel(RSB_CCR_SDA_OUT_DELAY(clk_delay) | RSB_CCR_CLK_DIV(clk_div - 1),
               rsb->regs + RSB_CCR);

        return 0;

err_clk_disable:
        clk_disable_unprepare(rsb->clk);

        return ret;
}

static void sunxi_rsb_hw_exit(struct sunxi_rsb *rsb)
{
        reset_control_assert(rsb->rstc);

        /* Keep the clock and PM reference counts consistent. */
        if (!pm_runtime_status_suspended(rsb->dev))
                clk_disable_unprepare(rsb->clk);
}

static int __maybe_unused sunxi_rsb_runtime_suspend(struct device *dev)
{
        struct sunxi_rsb *rsb = dev_get_drvdata(dev);

        clk_disable_unprepare(rsb->clk);

        return 0;
}

static int __maybe_unused sunxi_rsb_runtime_resume(struct device *dev)
{
        struct sunxi_rsb *rsb = dev_get_drvdata(dev);

        return clk_prepare_enable(rsb->clk);
}

static int __maybe_unused sunxi_rsb_suspend(struct device *dev)
{
        struct sunxi_rsb *rsb = dev_get_drvdata(dev);

        sunxi_rsb_hw_exit(rsb);

        return 0;
}

static int __maybe_unused sunxi_rsb_resume(struct device *dev)
{
        struct sunxi_rsb *rsb = dev_get_drvdata(dev);

        return sunxi_rsb_hw_init(rsb);
}

static int sunxi_rsb_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *np = dev->of_node;
        struct sunxi_rsb *rsb;
        u32 clk_freq = 3000000;
        int irq, ret;

        of_property_read_u32(np, "clock-frequency", &clk_freq);
        if (clk_freq > RSB_MAX_FREQ)
                return dev_err_probe(dev, -EINVAL,
                                     "clock-frequency (%u Hz) is too high (max = 20MHz)\n",
                                     clk_freq);

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

        rsb->dev = dev;
        rsb->clk_freq = clk_freq;
        platform_set_drvdata(pdev, rsb);
        rsb->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(rsb->regs))
                return PTR_ERR(rsb->regs);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        rsb->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(rsb->clk))
                return dev_err_probe(dev, PTR_ERR(rsb->clk),
                                     "failed to retrieve clk\n");

        rsb->rstc = devm_reset_control_get(dev, NULL);
        if (IS_ERR(rsb->rstc))
                return dev_err_probe(dev, PTR_ERR(rsb->rstc),
                                     "failed to retrieve reset controller\n");

        init_completion(&rsb->complete);
        mutex_init(&rsb->lock);

        ret = devm_request_irq(dev, irq, sunxi_rsb_irq, 0, RSB_CTRL_NAME, rsb);
        if (ret)
                return dev_err_probe(dev, ret,
                                     "can't register interrupt handler irq %d\n", irq);

        ret = sunxi_rsb_hw_init(rsb);
        if (ret)
                return ret;

        /* initialize all devices on the bus into RSB mode */
        ret = sunxi_rsb_init_device_mode(rsb);
        if (ret)
                dev_warn(dev, "Initialize device mode failed: %d\n", ret);

        pm_suspend_ignore_children(dev, true);
        pm_runtime_set_active(dev);
        pm_runtime_set_autosuspend_delay(dev, MSEC_PER_SEC);
        pm_runtime_use_autosuspend(dev);
        pm_runtime_enable(dev);

        of_rsb_register_devices(rsb);

        return 0;
}

static void sunxi_rsb_remove(struct platform_device *pdev)
{
        struct sunxi_rsb *rsb = platform_get_drvdata(pdev);

        device_for_each_child(rsb->dev, NULL, sunxi_rsb_remove_devices);
        pm_runtime_disable(&pdev->dev);
        sunxi_rsb_hw_exit(rsb);
}

static const struct dev_pm_ops sunxi_rsb_dev_pm_ops = {
        SET_RUNTIME_PM_OPS(sunxi_rsb_runtime_suspend,
                           sunxi_rsb_runtime_resume, NULL)
        SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(sunxi_rsb_suspend, sunxi_rsb_resume)
};

static const struct of_device_id sunxi_rsb_of_match_table[] = {
        { .compatible = "allwinner,sun8i-a23-rsb" },
        {}
};
MODULE_DEVICE_TABLE(of, sunxi_rsb_of_match_table);

static struct platform_driver sunxi_rsb_driver = {
        .probe = sunxi_rsb_probe,
        .remove = sunxi_rsb_remove,
        .driver = {
                .name = RSB_CTRL_NAME,
                .of_match_table = sunxi_rsb_of_match_table,
                .pm = &sunxi_rsb_dev_pm_ops,
        },
};

static int __init sunxi_rsb_init(void)
{
        int ret;

        ret = bus_register(&sunxi_rsb_bus);
        if (ret) {
                pr_err("failed to register sunxi sunxi_rsb bus: %d\n", ret);
                return ret;
        }

        ret = platform_driver_register(&sunxi_rsb_driver);
        if (ret) {
                bus_unregister(&sunxi_rsb_bus);
                return ret;
        }

        return 0;
}
module_init(sunxi_rsb_init);

static void __exit sunxi_rsb_exit(void)
{
        platform_driver_unregister(&sunxi_rsb_driver);
        bus_unregister(&sunxi_rsb_bus);
}
module_exit(sunxi_rsb_exit);

MODULE_AUTHOR("Chen-Yu Tsai <wens@csie.org>");
MODULE_DESCRIPTION("Allwinner sunXi Reduced Serial Bus controller driver");
MODULE_LICENSE("GPL v2");