/*
 * Copyright (c) 2015-2016, IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/atomic.h>
#include <linux/bt-bmc.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/mfd/syscon.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
#include <linux/regmap.h>
#include <linux/sched.h>
#include <linux/timer.h>

/*
 * This is a BMC device used to communicate to the host
 */
#define DEVICE_NAME     "ipmi-bt-host"

#define BT_IO_BASE      0xe4
#define BT_IRQ          10

#define BT_CR0          0x0
#define   BT_CR0_IO_BASE                16
#define   BT_CR0_IRQ                    12
#define   BT_CR0_EN_CLR_SLV_RDP         0x8
#define   BT_CR0_EN_CLR_SLV_WRP         0x4
#define   BT_CR0_ENABLE_IBT             0x1
#define BT_CR1          0x4
#define   BT_CR1_IRQ_H2B        0x01
#define   BT_CR1_IRQ_HBUSY      0x40
#define BT_CR2          0x8
#define   BT_CR2_IRQ_H2B        0x01
#define   BT_CR2_IRQ_HBUSY      0x40
#define BT_CR3          0xc
#define BT_CTRL         0x10
#define   BT_CTRL_B_BUSY                0x80
#define   BT_CTRL_H_BUSY                0x40
#define   BT_CTRL_OEM0                  0x20
#define   BT_CTRL_SMS_ATN               0x10
#define   BT_CTRL_B2H_ATN               0x08
#define   BT_CTRL_H2B_ATN               0x04
#define   BT_CTRL_CLR_RD_PTR            0x02
#define   BT_CTRL_CLR_WR_PTR            0x01
#define BT_BMC2HOST     0x14
#define BT_INTMASK      0x18
#define   BT_INTMASK_B2H_IRQEN          0x01
#define   BT_INTMASK_B2H_IRQ            0x02
#define   BT_INTMASK_BMC_HWRST          0x80

#define BT_BMC_BUFFER_SIZE 256

struct bt_bmc {
        struct device           dev;
        struct miscdevice       miscdev;
        struct regmap           *map;
        int                     offset;
        int                     irq;
        wait_queue_head_t       queue;
        struct timer_list       poll_timer;
        struct mutex            mutex;
};

static atomic_t open_count = ATOMIC_INIT(0);

static const struct regmap_config bt_regmap_cfg = {
        .reg_bits = 32,
        .val_bits = 32,
        .reg_stride = 4,
};

static u8 bt_inb(struct bt_bmc *bt_bmc, int reg)
{
        uint32_t val = 0;
        int rc;

        rc = regmap_read(bt_bmc->map, bt_bmc->offset + reg, &val);
        WARN(rc != 0, "regmap_read() failed: %d\n", rc);

        return rc == 0 ? (u8) val : 0;
}

static void bt_outb(struct bt_bmc *bt_bmc, u8 data, int reg)
{
        int rc;

        rc = regmap_write(bt_bmc->map, bt_bmc->offset + reg, data);
        WARN(rc != 0, "regmap_write() failed: %d\n", rc);
}

static void clr_rd_ptr(struct bt_bmc *bt_bmc)
{
        bt_outb(bt_bmc, BT_CTRL_CLR_RD_PTR, BT_CTRL);
}

static void clr_wr_ptr(struct bt_bmc *bt_bmc)
{
        bt_outb(bt_bmc, BT_CTRL_CLR_WR_PTR, BT_CTRL);
}

static void clr_h2b_atn(struct bt_bmc *bt_bmc)
{
        bt_outb(bt_bmc, BT_CTRL_H2B_ATN, BT_CTRL);
}

static void set_b_busy(struct bt_bmc *bt_bmc)
{
        if (!(bt_inb(bt_bmc, BT_CTRL) & BT_CTRL_B_BUSY))
                bt_outb(bt_bmc, BT_CTRL_B_BUSY, BT_CTRL);
}

static void clr_b_busy(struct bt_bmc *bt_bmc)
{
        if (bt_inb(bt_bmc, BT_CTRL) & BT_CTRL_B_BUSY)
                bt_outb(bt_bmc, BT_CTRL_B_BUSY, BT_CTRL);
}

static void set_b2h_atn(struct bt_bmc *bt_bmc)
{
        bt_outb(bt_bmc, BT_CTRL_B2H_ATN, BT_CTRL);
}

static u8 bt_read(struct bt_bmc *bt_bmc)
{
        return bt_inb(bt_bmc, BT_BMC2HOST);
}

static ssize_t bt_readn(struct bt_bmc *bt_bmc, u8 *buf, size_t n)
{
        int i;

        for (i = 0; i < n; i++)
                buf[i] = bt_read(bt_bmc);
        return n;
}

static void bt_write(struct bt_bmc *bt_bmc, u8 c)
{
        bt_outb(bt_bmc, c, BT_BMC2HOST);
}

static ssize_t bt_writen(struct bt_bmc *bt_bmc, u8 *buf, size_t n)
{
        int i;

        for (i = 0; i < n; i++)
                bt_write(bt_bmc, buf[i]);
        return n;
}

static void set_sms_atn(struct bt_bmc *bt_bmc)
{
        bt_outb(bt_bmc, BT_CTRL_SMS_ATN, BT_CTRL);
}

static struct bt_bmc *file_bt_bmc(struct file *file)
{
        return container_of(file->private_data, struct bt_bmc, miscdev);
}

static int bt_bmc_open(struct inode *inode, struct file *file)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);

        if (atomic_inc_return(&open_count) == 1) {
                clr_b_busy(bt_bmc);
                return 0;
        }

        atomic_dec(&open_count);
        return -EBUSY;
}

/*
 * The BT (Block Transfer) interface means that entire messages are
 * buffered by the host before a notification is sent to the BMC that
 * there is data to be read. The first byte is the length and the
 * message data follows. The read operation just tries to capture the
 * whole before returning it to userspace.
 *
 * BT Message format :
 *
 *    Byte 1  Byte 2     Byte 3  Byte 4  Byte 5:N
 *    Length  NetFn/LUN  Seq     Cmd     Data
 *
 */
static ssize_t bt_bmc_read(struct file *file, char __user *buf,
                           size_t count, loff_t *ppos)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);
        u8 len;
        int len_byte = 1;
        u8 kbuffer[BT_BMC_BUFFER_SIZE];
        ssize_t ret = 0;
        ssize_t nread;

        if (!access_ok(VERIFY_WRITE, buf, count))
                return -EFAULT;

        WARN_ON(*ppos);

        if (wait_event_interruptible(bt_bmc->queue,
                                     bt_inb(bt_bmc, BT_CTRL) & BT_CTRL_H2B_ATN))
                return -ERESTARTSYS;

        mutex_lock(&bt_bmc->mutex);

        if (unlikely(!(bt_inb(bt_bmc, BT_CTRL) & BT_CTRL_H2B_ATN))) {
                ret = -EIO;
                goto out_unlock;
        }

        set_b_busy(bt_bmc);
        clr_h2b_atn(bt_bmc);
        clr_rd_ptr(bt_bmc);

        /*
         * The BT frames start with the message length, which does not
         * include the length byte.
         */
        kbuffer[0] = bt_read(bt_bmc);
        len = kbuffer[0];

        /* We pass the length back to userspace as well */
        if (len + 1 > count)
                len = count - 1;

        while (len) {
                nread = min_t(ssize_t, len, sizeof(kbuffer) - len_byte);

                bt_readn(bt_bmc, kbuffer + len_byte, nread);

                if (copy_to_user(buf, kbuffer, nread + len_byte)) {
                        ret = -EFAULT;
                        break;
                }
                len -= nread;
                buf += nread + len_byte;
                ret += nread + len_byte;
                len_byte = 0;
        }

        clr_b_busy(bt_bmc);

out_unlock:
        mutex_unlock(&bt_bmc->mutex);
        return ret;
}

/*
 * BT Message response format :
 *
 *    Byte 1  Byte 2     Byte 3  Byte 4  Byte 5  Byte 6:N
 *    Length  NetFn/LUN  Seq     Cmd     Code    Data
 */
static ssize_t bt_bmc_write(struct file *file, const char __user *buf,
                            size_t count, loff_t *ppos)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);
        u8 kbuffer[BT_BMC_BUFFER_SIZE];
        ssize_t ret = 0;
        ssize_t nwritten;

        /*
         * send a minimum response size
         */
        if (count < 5)
                return -EINVAL;

        if (!access_ok(VERIFY_READ, buf, count))
                return -EFAULT;

        WARN_ON(*ppos);

        /*
         * There's no interrupt for clearing bmc busy so we have to
         * poll
         */
        if (wait_event_interruptible(bt_bmc->queue,
                                     !(bt_inb(bt_bmc, BT_CTRL) &
                                       (BT_CTRL_H_BUSY | BT_CTRL_B2H_ATN))))
                return -ERESTARTSYS;

        mutex_lock(&bt_bmc->mutex);

        if (unlikely(bt_inb(bt_bmc, BT_CTRL) &
                     (BT_CTRL_H_BUSY | BT_CTRL_B2H_ATN))) {
                ret = -EIO;
                goto out_unlock;
        }

        clr_wr_ptr(bt_bmc);

        while (count) {
                nwritten = min_t(ssize_t, count, sizeof(kbuffer));
                if (copy_from_user(&kbuffer, buf, nwritten)) {
                        ret = -EFAULT;
                        break;
                }

                bt_writen(bt_bmc, kbuffer, nwritten);

                count -= nwritten;
                buf += nwritten;
                ret += nwritten;
        }

        set_b2h_atn(bt_bmc);

out_unlock:
        mutex_unlock(&bt_bmc->mutex);
        return ret;
}

static long bt_bmc_ioctl(struct file *file, unsigned int cmd,
                         unsigned long param)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);

        switch (cmd) {
        case BT_BMC_IOCTL_SMS_ATN:
                set_sms_atn(bt_bmc);
                return 0;
        }
        return -EINVAL;
}

static int bt_bmc_release(struct inode *inode, struct file *file)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);

        atomic_dec(&open_count);
        set_b_busy(bt_bmc);
        return 0;
}

static unsigned int bt_bmc_poll(struct file *file, poll_table *wait)
{
        struct bt_bmc *bt_bmc = file_bt_bmc(file);
        unsigned int mask = 0;
        u8 ctrl;

        poll_wait(file, &bt_bmc->queue, wait);

        ctrl = bt_inb(bt_bmc, BT_CTRL);

        if (ctrl & BT_CTRL_H2B_ATN)
                mask |= POLLIN;

        if (!(ctrl & (BT_CTRL_H_BUSY | BT_CTRL_B2H_ATN)))
                mask |= POLLOUT;

        return mask;
}

static const struct file_operations bt_bmc_fops = {
        .owner          = THIS_MODULE,
        .open           = bt_bmc_open,
        .read           = bt_bmc_read,
        .write          = bt_bmc_write,
        .release        = bt_bmc_release,
        .poll           = bt_bmc_poll,
        .unlocked_ioctl = bt_bmc_ioctl,
};

static void poll_timer(unsigned long data)
{
        struct bt_bmc *bt_bmc = (void *)data;

        bt_bmc->poll_timer.expires += msecs_to_jiffies(500);
        wake_up(&bt_bmc->queue);
        add_timer(&bt_bmc->poll_timer);
}

static irqreturn_t bt_bmc_irq(int irq, void *arg)
{
        struct bt_bmc *bt_bmc = arg;
        u32 reg;
        int rc;

        rc = regmap_read(bt_bmc->map, bt_bmc->offset + BT_CR2, &reg);
        if (rc)
                return IRQ_NONE;

        reg &= BT_CR2_IRQ_H2B | BT_CR2_IRQ_HBUSY;
        if (!reg)
                return IRQ_NONE;

        /* ack pending IRQs */
        regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR2, reg);

        wake_up(&bt_bmc->queue);
        return IRQ_HANDLED;
}

static int bt_bmc_config_irq(struct bt_bmc *bt_bmc,
                             struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        int rc;

        bt_bmc->irq = platform_get_irq(pdev, 0);
        if (!bt_bmc->irq)
                return -ENODEV;

        rc = devm_request_irq(dev, bt_bmc->irq, bt_bmc_irq, IRQF_SHARED,
                              DEVICE_NAME, bt_bmc);
        if (rc < 0) {
                dev_warn(dev, "Unable to request IRQ %d\n", bt_bmc->irq);
                bt_bmc->irq = 0;
                return rc;
        }

        /*
         * Configure IRQs on the bmc clearing the H2B and HBUSY bits;
         * H2B will be asserted when the bmc has data for us; HBUSY
         * will be cleared (along with B2H) when we can write the next
         * message to the BT buffer
         */
        rc = regmap_update_bits(bt_bmc->map, bt_bmc->offset + BT_CR1,
                                (BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY),
                                (BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY));

        return rc;
}

static int bt_bmc_probe(struct platform_device *pdev)
{
        struct bt_bmc *bt_bmc;
        struct device *dev;
        int rc;

        if (!pdev || !pdev->dev.of_node)
                return -ENODEV;

        dev = &pdev->dev;
        dev_info(dev, "Found bt bmc device\n");

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

        dev_set_drvdata(&pdev->dev, bt_bmc);

        bt_bmc->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
        if (IS_ERR(bt_bmc->map)) {
                struct resource *res;
                void __iomem *base;

                /*
                 * Assume it's not the MFD-based devicetree description, in
                 * which case generate a regmap ourselves
                 */
                res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
                base = devm_ioremap_resource(&pdev->dev, res);
                if (IS_ERR(base))
                        return PTR_ERR(base);

                bt_bmc->map = devm_regmap_init_mmio(dev, base, &bt_regmap_cfg);
                bt_bmc->offset = 0;
        } else {
                rc = of_property_read_u32(dev->of_node, "reg", &bt_bmc->offset);
                if (rc)
                        return rc;
        }

        mutex_init(&bt_bmc->mutex);
        init_waitqueue_head(&bt_bmc->queue);

        bt_bmc->miscdev.minor   = MISC_DYNAMIC_MINOR,
                bt_bmc->miscdev.name    = DEVICE_NAME,
                bt_bmc->miscdev.fops    = &bt_bmc_fops,
                bt_bmc->miscdev.parent = dev;
        rc = misc_register(&bt_bmc->miscdev);
        if (rc) {
                dev_err(dev, "Unable to register misc device\n");
                return rc;
        }

        bt_bmc_config_irq(bt_bmc, pdev);

        if (bt_bmc->irq) {
                dev_info(dev, "Using IRQ %d\n", bt_bmc->irq);
        } else {
                dev_info(dev, "No IRQ; using timer\n");
                setup_timer(&bt_bmc->poll_timer, poll_timer,
                            (unsigned long)bt_bmc);
                bt_bmc->poll_timer.expires = jiffies + msecs_to_jiffies(10);
                add_timer(&bt_bmc->poll_timer);
        }

        regmap_write(bt_bmc->map, bt_bmc->offset + BT_CR0,
                     (BT_IO_BASE << BT_CR0_IO_BASE) |
                     (BT_IRQ << BT_CR0_IRQ) |
                     BT_CR0_EN_CLR_SLV_RDP |
                     BT_CR0_EN_CLR_SLV_WRP |
                     BT_CR0_ENABLE_IBT);

        clr_b_busy(bt_bmc);

        return 0;
}

static int bt_bmc_remove(struct platform_device *pdev)
{
        struct bt_bmc *bt_bmc = dev_get_drvdata(&pdev->dev);

        misc_deregister(&bt_bmc->miscdev);
        if (!bt_bmc->irq)
                del_timer_sync(&bt_bmc->poll_timer);
        return 0;
}

static const struct of_device_id bt_bmc_match[] = {
        { .compatible = "aspeed,ast2400-ibt-bmc" },
        { .compatible = "aspeed,ast2500-ibt-bmc" },
        { },
};

static struct platform_driver bt_bmc_driver = {
        .driver = {
                .name           = DEVICE_NAME,
                .of_match_table = bt_bmc_match,
        },
        .probe = bt_bmc_probe,
        .remove = bt_bmc_remove,
};

module_platform_driver(bt_bmc_driver);

MODULE_DEVICE_TABLE(of, bt_bmc_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alistair Popple <alistair@popple.id.au>");
MODULE_DESCRIPTION("Linux device interface to the IPMI BT interface");