/*
 * PowerMac G5 SMU driver
 *
 * Copyright 2004 J. Mayer <l_indien@magic.fr>
 * Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
 *
 * Released under the term of the GNU GPL v2.
 */

/*
 * TODO:
 *  - maybe add timeout to commands ?
 *  - blocking version of time functions
 *  - polling version of i2c commands (including timer that works with
 *    interrupts off)
 *  - maybe avoid some data copies with i2c by directly using the smu cmd
 *    buffer and a lower level internal interface
 *  - understand SMU -> CPU events and implement reception of them via
 *    the userland interface
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/dmapool.h>
#include <linux/bootmem.h>
#include <linux/vmalloc.h>
#include <linux/highmem.h>
#include <linux/jiffies.h>
#include <linux/interrupt.h>
#include <linux/rtc.h>
#include <linux/completion.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/slab.h>

#include <asm/byteorder.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/pmac_feature.h>
#include <asm/smu.h>
#include <asm/sections.h>
#include <asm/uaccess.h>

#define VERSION "0.7"
#define AUTHOR  "(c) 2005 Benjamin Herrenschmidt, IBM Corp."

#undef DEBUG_SMU

#ifdef DEBUG_SMU
#define DPRINTK(fmt, args...) do { printk(KERN_DEBUG fmt , ##args); } while (0)
#else
#define DPRINTK(fmt, args...) do { } while (0)
#endif

/*
 * This is the command buffer passed to the SMU hardware
 */
#define SMU_MAX_DATA    254

struct smu_cmd_buf {
        u8 cmd;
        u8 length;
        u8 data[SMU_MAX_DATA];
};

struct smu_device {
        spinlock_t              lock;
        struct device_node      *of_node;
        struct platform_device  *of_dev;
        int                     doorbell;       /* doorbell gpio */
        u32 __iomem             *db_buf;        /* doorbell buffer */
        struct device_node      *db_node;
        unsigned int            db_irq;
        int                     msg;
        struct device_node      *msg_node;
        unsigned int            msg_irq;
        struct smu_cmd_buf      *cmd_buf;       /* command buffer virtual */
        u32                     cmd_buf_abs;    /* command buffer absolute */
        struct list_head        cmd_list;
        struct smu_cmd          *cmd_cur;       /* pending command */
        int                     broken_nap;
        struct list_head        cmd_i2c_list;
        struct smu_i2c_cmd      *cmd_i2c_cur;   /* pending i2c command */
        struct timer_list       i2c_timer;
};

/*
 * I don't think there will ever be more than one SMU, so
 * for now, just hard code that
 */
static DEFINE_MUTEX(smu_mutex);
static struct smu_device        *smu;
static DEFINE_MUTEX(smu_part_access);
static int smu_irq_inited;

static void smu_i2c_retry(unsigned long data);

/*
 * SMU driver low level stuff
 */

static void smu_start_cmd(void)
{
        unsigned long faddr, fend;
        struct smu_cmd *cmd;

        if (list_empty(&smu->cmd_list))
                return;

        /* Fetch first command in queue */
        cmd = list_entry(smu->cmd_list.next, struct smu_cmd, link);
        smu->cmd_cur = cmd;
        list_del(&cmd->link);

        DPRINTK("SMU: starting cmd %x, %d bytes data\n", cmd->cmd,
                cmd->data_len);
        DPRINTK("SMU: data buffer: %8ph\n", cmd->data_buf);

        /* Fill the SMU command buffer */
        smu->cmd_buf->cmd = cmd->cmd;
        smu->cmd_buf->length = cmd->data_len;
        memcpy(smu->cmd_buf->data, cmd->data_buf, cmd->data_len);

        /* Flush command and data to RAM */
        faddr = (unsigned long)smu->cmd_buf;
        fend = faddr + smu->cmd_buf->length + 2;
        flush_inval_dcache_range(faddr, fend);


        /* We also disable NAP mode for the duration of the command
         * on U3 based machines.
         * This is slightly racy as it can be written back to 1 by a sysctl
         * but that never happens in practice. There seem to be an issue with
         * U3 based machines such as the iMac G5 where napping for the
         * whole duration of the command prevents the SMU from fetching it
         * from memory. This might be related to the strange i2c based
         * mechanism the SMU uses to access memory.
         */
        if (smu->broken_nap)
                powersave_nap = 0;

        /* This isn't exactly a DMA mapping here, I suspect
         * the SMU is actually communicating with us via i2c to the
         * northbridge or the CPU to access RAM.
         */
        writel(smu->cmd_buf_abs, smu->db_buf);

        /* Ring the SMU doorbell */
        pmac_do_feature_call(PMAC_FTR_WRITE_GPIO, NULL, smu->doorbell, 4);
}


static irqreturn_t smu_db_intr(int irq, void *arg)
{
        unsigned long flags;
        struct smu_cmd *cmd;
        void (*done)(struct smu_cmd *cmd, void *misc) = NULL;
        void *misc = NULL;
        u8 gpio;
        int rc = 0;

        /* SMU completed the command, well, we hope, let's make sure
         * of it
         */
        spin_lock_irqsave(&smu->lock, flags);

        gpio = pmac_do_feature_call(PMAC_FTR_READ_GPIO, NULL, smu->doorbell);
        if ((gpio & 7) != 7) {
                spin_unlock_irqrestore(&smu->lock, flags);
                return IRQ_HANDLED;
        }

        cmd = smu->cmd_cur;
        smu->cmd_cur = NULL;
        if (cmd == NULL)
                goto bail;

        if (rc == 0) {
                unsigned long faddr;
                int reply_len;
                u8 ack;

                /* CPU might have brought back the cache line, so we need
                 * to flush again before peeking at the SMU response. We
                 * flush the entire buffer for now as we haven't read the
                 * reply length (it's only 2 cache lines anyway)
                 */
                faddr = (unsigned long)smu->cmd_buf;
                flush_inval_dcache_range(faddr, faddr + 256);

                /* Now check ack */
                ack = (~cmd->cmd) & 0xff;
                if (ack != smu->cmd_buf->cmd) {
                        DPRINTK("SMU: incorrect ack, want %x got %x\n",
                                ack, smu->cmd_buf->cmd);
                        rc = -EIO;
                }
                reply_len = rc == 0 ? smu->cmd_buf->length : 0;
                DPRINTK("SMU: reply len: %d\n", reply_len);
                if (reply_len > cmd->reply_len) {
                        printk(KERN_WARNING "SMU: reply buffer too small,"
                               "got %d bytes for a %d bytes buffer\n",
                               reply_len, cmd->reply_len);
                        reply_len = cmd->reply_len;
                }
                cmd->reply_len = reply_len;
                if (cmd->reply_buf && reply_len)
                        memcpy(cmd->reply_buf, smu->cmd_buf->data, reply_len);
        }

        /* Now complete the command. Write status last in order as we lost
         * ownership of the command structure as soon as it's no longer -1
         */
        done = cmd->done;
        misc = cmd->misc;
        mb();
        cmd->status = rc;

        /* Re-enable NAP mode */
        if (smu->broken_nap)
                powersave_nap = 1;
 bail:
        /* Start next command if any */
        smu_start_cmd();
        spin_unlock_irqrestore(&smu->lock, flags);

        /* Call command completion handler if any */
        if (done)
                done(cmd, misc);

        /* It's an edge interrupt, nothing to do */
        return IRQ_HANDLED;
}


static irqreturn_t smu_msg_intr(int irq, void *arg)
{
        /* I don't quite know what to do with this one, we seem to never
         * receive it, so I suspect we have to arm it someway in the SMU
         * to start getting events that way.
         */

        printk(KERN_INFO "SMU: message interrupt !\n");

        /* It's an edge interrupt, nothing to do */
        return IRQ_HANDLED;
}


/*
 * Queued command management.
 *
 */

int smu_queue_cmd(struct smu_cmd *cmd)
{
        unsigned long flags;

        if (smu == NULL)
                return -ENODEV;
        if (cmd->data_len > SMU_MAX_DATA ||
            cmd->reply_len > SMU_MAX_DATA)
                return -EINVAL;

        cmd->status = 1;
        spin_lock_irqsave(&smu->lock, flags);
        list_add_tail(&cmd->link, &smu->cmd_list);
        if (smu->cmd_cur == NULL)
                smu_start_cmd();
        spin_unlock_irqrestore(&smu->lock, flags);

        /* Workaround for early calls when irq isn't available */
        if (!smu_irq_inited || smu->db_irq == NO_IRQ)
                smu_spinwait_cmd(cmd);

        return 0;
}
EXPORT_SYMBOL(smu_queue_cmd);


int smu_queue_simple(struct smu_simple_cmd *scmd, u8 command,
                     unsigned int data_len,
                     void (*done)(struct smu_cmd *cmd, void *misc),
                     void *misc, ...)
{
        struct smu_cmd *cmd = &scmd->cmd;
        va_list list;
        int i;

        if (data_len > sizeof(scmd->buffer))
                return -EINVAL;

        memset(scmd, 0, sizeof(*scmd));
        cmd->cmd = command;
        cmd->data_len = data_len;
        cmd->data_buf = scmd->buffer;
        cmd->reply_len = sizeof(scmd->buffer);
        cmd->reply_buf = scmd->buffer;
        cmd->done = done;
        cmd->misc = misc;

        va_start(list, misc);
        for (i = 0; i < data_len; ++i)
                scmd->buffer[i] = (u8)va_arg(list, int);
        va_end(list);

        return smu_queue_cmd(cmd);
}
EXPORT_SYMBOL(smu_queue_simple);


void smu_poll(void)
{
        u8 gpio;

        if (smu == NULL)
                return;

        gpio = pmac_do_feature_call(PMAC_FTR_READ_GPIO, NULL, smu->doorbell);
        if ((gpio & 7) == 7)
                smu_db_intr(smu->db_irq, smu);
}
EXPORT_SYMBOL(smu_poll);


void smu_done_complete(struct smu_cmd *cmd, void *misc)
{
        struct completion *comp = misc;

        complete(comp);
}
EXPORT_SYMBOL(smu_done_complete);


void smu_spinwait_cmd(struct smu_cmd *cmd)
{
        while(cmd->status == 1)
                smu_poll();
}
EXPORT_SYMBOL(smu_spinwait_cmd);


/* RTC low level commands */
static inline int bcd2hex (int n)
{
        return (((n & 0xf0) >> 4) * 10) + (n & 0xf);
}


static inline int hex2bcd (int n)
{
        return ((n / 10) << 4) + (n % 10);
}


static inline void smu_fill_set_rtc_cmd(struct smu_cmd_buf *cmd_buf,
                                        struct rtc_time *time)
{
        cmd_buf->cmd = 0x8e;
        cmd_buf->length = 8;
        cmd_buf->data[0] = 0x80;
        cmd_buf->data[1] = hex2bcd(time->tm_sec);
        cmd_buf->data[2] = hex2bcd(time->tm_min);
        cmd_buf->data[3] = hex2bcd(time->tm_hour);
        cmd_buf->data[4] = time->tm_wday;
        cmd_buf->data[5] = hex2bcd(time->tm_mday);
        cmd_buf->data[6] = hex2bcd(time->tm_mon) + 1;
        cmd_buf->data[7] = hex2bcd(time->tm_year - 100);
}


int smu_get_rtc_time(struct rtc_time *time, int spinwait)
{
        struct smu_simple_cmd cmd;
        int rc;

        if (smu == NULL)
                return -ENODEV;

        memset(time, 0, sizeof(struct rtc_time));
        rc = smu_queue_simple(&cmd, SMU_CMD_RTC_COMMAND, 1, NULL, NULL,
                              SMU_CMD_RTC_GET_DATETIME);
        if (rc)
                return rc;
        smu_spinwait_simple(&cmd);

        time->tm_sec = bcd2hex(cmd.buffer[0]);
        time->tm_min = bcd2hex(cmd.buffer[1]);
        time->tm_hour = bcd2hex(cmd.buffer[2]);
        time->tm_wday = bcd2hex(cmd.buffer[3]);
        time->tm_mday = bcd2hex(cmd.buffer[4]);
        time->tm_mon = bcd2hex(cmd.buffer[5]) - 1;
        time->tm_year = bcd2hex(cmd.buffer[6]) + 100;

        return 0;
}


int smu_set_rtc_time(struct rtc_time *time, int spinwait)
{
        struct smu_simple_cmd cmd;
        int rc;

        if (smu == NULL)
                return -ENODEV;

        rc = smu_queue_simple(&cmd, SMU_CMD_RTC_COMMAND, 8, NULL, NULL,
                              SMU_CMD_RTC_SET_DATETIME,
                              hex2bcd(time->tm_sec),
                              hex2bcd(time->tm_min),
                              hex2bcd(time->tm_hour),
                              time->tm_wday,
                              hex2bcd(time->tm_mday),
                              hex2bcd(time->tm_mon) + 1,
                              hex2bcd(time->tm_year - 100));
        if (rc)
                return rc;
        smu_spinwait_simple(&cmd);

        return 0;
}


void smu_shutdown(void)
{
        struct smu_simple_cmd cmd;

        if (smu == NULL)
                return;

        if (smu_queue_simple(&cmd, SMU_CMD_POWER_COMMAND, 9, NULL, NULL,
                             'S', 'H', 'U', 'T', 'D', 'O', 'W', 'N', 0))
                return;
        smu_spinwait_simple(&cmd);
        for (;;)
                ;
}


void smu_restart(void)
{
        struct smu_simple_cmd cmd;

        if (smu == NULL)
                return;

        if (smu_queue_simple(&cmd, SMU_CMD_POWER_COMMAND, 8, NULL, NULL,
                             'R', 'E', 'S', 'T', 'A', 'R', 'T', 0))
                return;
        smu_spinwait_simple(&cmd);
        for (;;)
                ;
}


int smu_present(void)
{
        return smu != NULL;
}
EXPORT_SYMBOL(smu_present);


int __init smu_init (void)
{
        struct device_node *np;
        const u32 *data;
        int ret = 0;

        np = of_find_node_by_type(NULL, "smu");
        if (np == NULL)
                return -ENODEV;

        printk(KERN_INFO "SMU: Driver %s %s\n", VERSION, AUTHOR);

        if (smu_cmdbuf_abs == 0) {
                printk(KERN_ERR "SMU: Command buffer not allocated !\n");
                ret = -EINVAL;
                goto fail_np;
        }

        smu = alloc_bootmem(sizeof(struct smu_device));

        spin_lock_init(&smu->lock);
        INIT_LIST_HEAD(&smu->cmd_list);
        INIT_LIST_HEAD(&smu->cmd_i2c_list);
        smu->of_node = np;
        smu->db_irq = NO_IRQ;
        smu->msg_irq = NO_IRQ;

        /* smu_cmdbuf_abs is in the low 2G of RAM, can be converted to a
         * 32 bits value safely
         */
        smu->cmd_buf_abs = (u32)smu_cmdbuf_abs;
        smu->cmd_buf = __va(smu_cmdbuf_abs);

        smu->db_node = of_find_node_by_name(NULL, "smu-doorbell");
        if (smu->db_node == NULL) {
                printk(KERN_ERR "SMU: Can't find doorbell GPIO !\n");
                ret = -ENXIO;
                goto fail_bootmem;
        }
        data = of_get_property(smu->db_node, "reg", NULL);
        if (data == NULL) {
                printk(KERN_ERR "SMU: Can't find doorbell GPIO address !\n");
                ret = -ENXIO;
                goto fail_db_node;
        }

        /* Current setup has one doorbell GPIO that does both doorbell
         * and ack. GPIOs are at 0x50, best would be to find that out
         * in the device-tree though.
         */
        smu->doorbell = *data;
        if (smu->doorbell < 0x50)
                smu->doorbell += 0x50;

        /* Now look for the smu-interrupt GPIO */
        do {
                smu->msg_node = of_find_node_by_name(NULL, "smu-interrupt");
                if (smu->msg_node == NULL)
                        break;
                data = of_get_property(smu->msg_node, "reg", NULL);
                if (data == NULL) {
                        of_node_put(smu->msg_node);
                        smu->msg_node = NULL;
                        break;
                }
                smu->msg = *data;
                if (smu->msg < 0x50)
                        smu->msg += 0x50;
        } while(0);

        /* Doorbell buffer is currently hard-coded, I didn't find a proper
         * device-tree entry giving the address. Best would probably to use
         * an offset for K2 base though, but let's do it that way for now.
         */
        smu->db_buf = ioremap(0x8000860c, 0x1000);
        if (smu->db_buf == NULL) {
                printk(KERN_ERR "SMU: Can't map doorbell buffer pointer !\n");
                ret = -ENXIO;
                goto fail_msg_node;
        }

        /* U3 has an issue with NAP mode when issuing SMU commands */
        smu->broken_nap = pmac_get_uninorth_variant() < 4;
        if (smu->broken_nap)
                printk(KERN_INFO "SMU: using NAP mode workaround\n");

        sys_ctrler = SYS_CTRLER_SMU;
        return 0;

fail_msg_node:
        if (smu->msg_node)
                of_node_put(smu->msg_node);
fail_db_node:
        of_node_put(smu->db_node);
fail_bootmem:
        free_bootmem(__pa(smu), sizeof(struct smu_device));
        smu = NULL;
fail_np:
        of_node_put(np);
        return ret;
}


static int smu_late_init(void)
{
        if (!smu)
                return 0;

        init_timer(&smu->i2c_timer);
        smu->i2c_timer.function = smu_i2c_retry;
        smu->i2c_timer.data = (unsigned long)smu;

        if (smu->db_node) {
                smu->db_irq = irq_of_parse_and_map(smu->db_node, 0);
                if (smu->db_irq == NO_IRQ)
                        printk(KERN_ERR "smu: failed to map irq for node %s\n",
                               smu->db_node->full_name);
        }
        if (smu->msg_node) {
                smu->msg_irq = irq_of_parse_and_map(smu->msg_node, 0);
                if (smu->msg_irq == NO_IRQ)
                        printk(KERN_ERR "smu: failed to map irq for node %s\n",
                               smu->msg_node->full_name);
        }

        /*
         * Try to request the interrupts
         */

        if (smu->db_irq != NO_IRQ) {
                if (request_irq(smu->db_irq, smu_db_intr,
                                IRQF_SHARED, "SMU doorbell", smu) < 0) {
                        printk(KERN_WARNING "SMU: can't "
                               "request interrupt %d\n",
                               smu->db_irq);
                        smu->db_irq = NO_IRQ;
                }
        }

        if (smu->msg_irq != NO_IRQ) {
                if (request_irq(smu->msg_irq, smu_msg_intr,
                                IRQF_SHARED, "SMU message", smu) < 0) {
                        printk(KERN_WARNING "SMU: can't "
                               "request interrupt %d\n",
                               smu->msg_irq);
                        smu->msg_irq = NO_IRQ;
                }
        }

        smu_irq_inited = 1;
        return 0;
}
/* This has to be before arch_initcall as the low i2c stuff relies on the
 * above having been done before we reach arch_initcalls
 */
core_initcall(smu_late_init);

/*
 * sysfs visibility
 */

static void smu_expose_childs(struct work_struct *unused)
{
        struct device_node *np;

        for (np = NULL; (np = of_get_next_child(smu->of_node, np)) != NULL;)
                if (of_device_is_compatible(np, "smu-sensors"))
                        of_platform_device_create(np, "smu-sensors",
                                                  &smu->of_dev->dev);
}

static DECLARE_WORK(smu_expose_childs_work, smu_expose_childs);

static int smu_platform_probe(struct platform_device* dev)
{
        if (!smu)
                return -ENODEV;
        smu->of_dev = dev;

        /*
         * Ok, we are matched, now expose all i2c busses. We have to defer
         * that unfortunately or it would deadlock inside the device model
         */
        schedule_work(&smu_expose_childs_work);

        return 0;
}

static const struct of_device_id smu_platform_match[] =
{
        {
                .type           = "smu",
        },
        {},
};

static struct platform_driver smu_of_platform_driver =
{
        .driver = {
                .name = "smu",
                .owner = THIS_MODULE,
                .of_match_table = smu_platform_match,
        },
        .probe          = smu_platform_probe,
};

static int __init smu_init_sysfs(void)
{
        /*
         * For now, we don't power manage machines with an SMU chip,
         * I'm a bit too far from figuring out how that works with those
         * new chipsets, but that will come back and bite us
         */
        platform_driver_register(&smu_of_platform_driver);
        return 0;
}

device_initcall(smu_init_sysfs);

struct platform_device *smu_get_ofdev(void)
{
        if (!smu)
                return NULL;
        return smu->of_dev;
}

EXPORT_SYMBOL_GPL(smu_get_ofdev);

/*
 * i2c interface
 */

static void smu_i2c_complete_command(struct smu_i2c_cmd *cmd, int fail)
{
        void (*done)(struct smu_i2c_cmd *cmd, void *misc) = cmd->done;
        void *misc = cmd->misc;
        unsigned long flags;

        /* Check for read case */
        if (!fail && cmd->read) {
                if (cmd->pdata[0] < 1)
                        fail = 1;
                else
                        memcpy(cmd->info.data, &cmd->pdata[1],
                               cmd->info.datalen);
        }

        DPRINTK("SMU: completing, success: %d\n", !fail);

        /* Update status and mark no pending i2c command with lock
         * held so nobody comes in while we dequeue an eventual
         * pending next i2c command
         */
        spin_lock_irqsave(&smu->lock, flags);
        smu->cmd_i2c_cur = NULL;
        wmb();
        cmd->status = fail ? -EIO : 0;

        /* Is there another i2c command waiting ? */
        if (!list_empty(&smu->cmd_i2c_list)) {
                struct smu_i2c_cmd *newcmd;

                /* Fetch it, new current, remove from list */
                newcmd = list_entry(smu->cmd_i2c_list.next,
                                    struct smu_i2c_cmd, link);
                smu->cmd_i2c_cur = newcmd;
                list_del(&cmd->link);

                /* Queue with low level smu */
                list_add_tail(&cmd->scmd.link, &smu->cmd_list);
                if (smu->cmd_cur == NULL)
                        smu_start_cmd();
        }
        spin_unlock_irqrestore(&smu->lock, flags);

        /* Call command completion handler if any */
        if (done)
                done(cmd, misc);

}


static void smu_i2c_retry(unsigned long data)
{
        struct smu_i2c_cmd      *cmd = smu->cmd_i2c_cur;

        DPRINTK("SMU: i2c failure, requeuing...\n");

        /* requeue command simply by resetting reply_len */
        cmd->pdata[0] = 0xff;
        cmd->scmd.reply_len = sizeof(cmd->pdata);
        smu_queue_cmd(&cmd->scmd);
}


static void smu_i2c_low_completion(struct smu_cmd *scmd, void *misc)
{
        struct smu_i2c_cmd      *cmd = misc;
        int                     fail = 0;

        DPRINTK("SMU: i2c compl. stage=%d status=%x pdata[0]=%x rlen: %x\n",
                cmd->stage, scmd->status, cmd->pdata[0], scmd->reply_len);

        /* Check for possible status */
        if (scmd->status < 0)
                fail = 1;
        else if (cmd->read) {
                if (cmd->stage == 0)
                        fail = cmd->pdata[0] != 0;
                else
                        fail = cmd->pdata[0] >= 0x80;
        } else {
                fail = cmd->pdata[0] != 0;
        }

        /* Handle failures by requeuing command, after 5ms interval
         */
        if (fail && --cmd->retries > 0) {
                DPRINTK("SMU: i2c failure, starting timer...\n");
                BUG_ON(cmd != smu->cmd_i2c_cur);
                if (!smu_irq_inited) {
                        mdelay(5);
                        smu_i2c_retry(0);
                        return;
                }
                mod_timer(&smu->i2c_timer, jiffies + msecs_to_jiffies(5));
                return;
        }

        /* If failure or stage 1, command is complete */
        if (fail || cmd->stage != 0) {
                smu_i2c_complete_command(cmd, fail);
                return;
        }

        DPRINTK("SMU: going to stage 1\n");

        /* Ok, initial command complete, now poll status */
        scmd->reply_buf = cmd->pdata;
        scmd->reply_len = sizeof(cmd->pdata);
        scmd->data_buf = cmd->pdata;
        scmd->data_len = 1;
        cmd->pdata[0] = 0;
        cmd->stage = 1;
        cmd->retries = 20;
        smu_queue_cmd(scmd);
}


int smu_queue_i2c(struct smu_i2c_cmd *cmd)
{
        unsigned long flags;

        if (smu == NULL)
                return -ENODEV;

        /* Fill most fields of scmd */
        cmd->scmd.cmd = SMU_CMD_I2C_COMMAND;
        cmd->scmd.done = smu_i2c_low_completion;
        cmd->scmd.misc = cmd;
        cmd->scmd.reply_buf = cmd->pdata;
        cmd->scmd.reply_len = sizeof(cmd->pdata);
        cmd->scmd.data_buf = (u8 *)(char *)&cmd->info;
        cmd->scmd.status = 1;
        cmd->stage = 0;
        cmd->pdata[0] = 0xff;
        cmd->retries = 20;
        cmd->status = 1;

        /* Check transfer type, sanitize some "info" fields
         * based on transfer type and do more checking
         */
        cmd->info.caddr = cmd->info.devaddr;
        cmd->read = cmd->info.devaddr & 0x01;
        switch(cmd->info.type) {
        case SMU_I2C_TRANSFER_SIMPLE:
                memset(&cmd->info.sublen, 0, 4);
                break;
        case SMU_I2C_TRANSFER_COMBINED:
                cmd->info.devaddr &= 0xfe;
        case SMU_I2C_TRANSFER_STDSUB:
                if (cmd->info.sublen > 3)
                        return -EINVAL;
                break;
        default:
                return -EINVAL;
        }

        /* Finish setting up command based on transfer direction
         */
        if (cmd->read) {
                if (cmd->info.datalen > SMU_I2C_READ_MAX)
                        return -EINVAL;
                memset(cmd->info.data, 0xff, cmd->info.datalen);
                cmd->scmd.data_len = 9;
        } else {
                if (cmd->info.datalen > SMU_I2C_WRITE_MAX)
                        return -EINVAL;
                cmd->scmd.data_len = 9 + cmd->info.datalen;
        }

        DPRINTK("SMU: i2c enqueuing command\n");
        DPRINTK("SMU:   %s, len=%d bus=%x addr=%x sub0=%x type=%x\n",
                cmd->read ? "read" : "write", cmd->info.datalen,
                cmd->info.bus, cmd->info.caddr,
                cmd->info.subaddr[0], cmd->info.type);


        /* Enqueue command in i2c list, and if empty, enqueue also in
         * main command list
         */
        spin_lock_irqsave(&smu->lock, flags);
        if (smu->cmd_i2c_cur == NULL) {
                smu->cmd_i2c_cur = cmd;
                list_add_tail(&cmd->scmd.link, &smu->cmd_list);
                if (smu->cmd_cur == NULL)
                        smu_start_cmd();
        } else
                list_add_tail(&cmd->link, &smu->cmd_i2c_list);
        spin_unlock_irqrestore(&smu->lock, flags);

        return 0;
}

/*
 * Handling of "partitions"
 */

static int smu_read_datablock(u8 *dest, unsigned int addr, unsigned int len)
{
        DECLARE_COMPLETION_ONSTACK(comp);
        unsigned int chunk;
        struct smu_cmd cmd;
        int rc;
        u8 params[8];

        /* We currently use a chunk size of 0xe. We could check the
         * SMU firmware version and use bigger sizes though
         */
        chunk = 0xe;

        while (len) {
                unsigned int clen = min(len, chunk);

                cmd.cmd = SMU_CMD_MISC_ee_COMMAND;
                cmd.data_len = 7;
                cmd.data_buf = params;
                cmd.reply_len = chunk;
                cmd.reply_buf = dest;
                cmd.done = smu_done_complete;
                cmd.misc = &comp;
                params[0] = SMU_CMD_MISC_ee_GET_DATABLOCK_REC;
                params[1] = 0x4;
                *((u32 *)&params[2]) = addr;
                params[6] = clen;

                rc = smu_queue_cmd(&cmd);
                if (rc)
                        return rc;
                wait_for_completion(&comp);
                if (cmd.status != 0)
                        return rc;
                if (cmd.reply_len != clen) {
                        printk(KERN_DEBUG "SMU: short read in "
                               "smu_read_datablock, got: %d, want: %d\n",
                               cmd.reply_len, clen);
                        return -EIO;
                }
                len -= clen;
                addr += clen;
                dest += clen;
        }
        return 0;
}

static struct smu_sdbp_header *smu_create_sdb_partition(int id)
{
        DECLARE_COMPLETION_ONSTACK(comp);
        struct smu_simple_cmd cmd;
        unsigned int addr, len, tlen;
        struct smu_sdbp_header *hdr;
        struct property *prop;

        /* First query the partition info */
        DPRINTK("SMU: Query partition infos ... (irq=%d)\n", smu->db_irq);
        smu_queue_simple(&cmd, SMU_CMD_PARTITION_COMMAND, 2,
                         smu_done_complete, &comp,
                         SMU_CMD_PARTITION_LATEST, id);
        wait_for_completion(&comp);
        DPRINTK("SMU: done, status: %d, reply_len: %d\n",
                cmd.cmd.status, cmd.cmd.reply_len);

        /* Partition doesn't exist (or other error) */
        if (cmd.cmd.status != 0 || cmd.cmd.reply_len != 6)
                return NULL;

        /* Fetch address and length from reply */
        addr = *((u16 *)cmd.buffer);
        len = cmd.buffer[3] << 2;
        /* Calucluate total length to allocate, including the 17 bytes
         * for "sdb-partition-XX" that we append at the end of the buffer
         */
        tlen = sizeof(struct property) + len + 18;

        prop = kzalloc(tlen, GFP_KERNEL);
        if (prop == NULL)
                return NULL;
        hdr = (struct smu_sdbp_header *)(prop + 1);
        prop->name = ((char *)prop) + tlen - 18;
        sprintf(prop->name, "sdb-partition-%02x", id);
        prop->length = len;
        prop->value = hdr;
        prop->next = NULL;

        /* Read the datablock */
        if (smu_read_datablock((u8 *)hdr, addr, len)) {
                printk(KERN_DEBUG "SMU: datablock read failed while reading "
                       "partition %02x !\n", id);
                goto failure;
        }

        /* Got it, check a few things and create the property */
        if (hdr->id != id) {
                printk(KERN_DEBUG "SMU: Reading partition %02x and got "
                       "%02x !\n", id, hdr->id);
                goto failure;
        }
        if (of_add_property(smu->of_node, prop)) {
                printk(KERN_DEBUG "SMU: Failed creating sdb-partition-%02x "
                       "property !\n", id);
                goto failure;
        }

        return hdr;
 failure:
        kfree(prop);
        return NULL;
}

/* Note: Only allowed to return error code in pointers (using ERR_PTR)
 * when interruptible is 1
 */
const struct smu_sdbp_header *__smu_get_sdb_partition(int id,
                unsigned int *size, int interruptible)
{
        char pname[32];
        const struct smu_sdbp_header *part;

        if (!smu)
                return NULL;

        sprintf(pname, "sdb-partition-%02x", id);

        DPRINTK("smu_get_sdb_partition(%02x)\n", id);

        if (interruptible) {
                int rc;
                rc = mutex_lock_interruptible(&smu_part_access);
                if (rc)
                        return ERR_PTR(rc);
        } else
                mutex_lock(&smu_part_access);

        part = of_get_property(smu->of_node, pname, size);
        if (part == NULL) {
                DPRINTK("trying to extract from SMU ...\n");
                part = smu_create_sdb_partition(id);
                if (part != NULL && size)
                        *size = part->len << 2;
        }
        mutex_unlock(&smu_part_access);
        return part;
}

const struct smu_sdbp_header *smu_get_sdb_partition(int id, unsigned int *size)
{
        return __smu_get_sdb_partition(id, size, 0);
}
EXPORT_SYMBOL(smu_get_sdb_partition);


/*
 * Userland driver interface
 */


static LIST_HEAD(smu_clist);
static DEFINE_SPINLOCK(smu_clist_lock);

enum smu_file_mode {
        smu_file_commands,
        smu_file_events,
        smu_file_closing
};

struct smu_private
{
        struct list_head        list;
        enum smu_file_mode      mode;
        int                     busy;
        struct smu_cmd          cmd;
        spinlock_t              lock;
        wait_queue_head_t       wait;
        u8                      buffer[SMU_MAX_DATA];
};


static int smu_open(struct inode *inode, struct file *file)
{
        struct smu_private *pp;
        unsigned long flags;

        pp = kzalloc(sizeof(struct smu_private), GFP_KERNEL);
        if (pp == 0)
                return -ENOMEM;
        spin_lock_init(&pp->lock);
        pp->mode = smu_file_commands;
        init_waitqueue_head(&pp->wait);

        mutex_lock(&smu_mutex);
        spin_lock_irqsave(&smu_clist_lock, flags);
        list_add(&pp->list, &smu_clist);
        spin_unlock_irqrestore(&smu_clist_lock, flags);
        file->private_data = pp;
        mutex_unlock(&smu_mutex);

        return 0;
}


static void smu_user_cmd_done(struct smu_cmd *cmd, void *misc)
{
        struct smu_private *pp = misc;

        wake_up_all(&pp->wait);
}


static ssize_t smu_write(struct file *file, const char __user *buf,
                         size_t count, loff_t *ppos)
{
        struct smu_private *pp = file->private_data;
        unsigned long flags;
        struct smu_user_cmd_hdr hdr;
        int rc = 0;

        if (pp->busy)
                return -EBUSY;
        else if (copy_from_user(&hdr, buf, sizeof(hdr)))
                return -EFAULT;
        else if (hdr.cmdtype == SMU_CMDTYPE_WANTS_EVENTS) {
                pp->mode = smu_file_events;
                return 0;
        } else if (hdr.cmdtype == SMU_CMDTYPE_GET_PARTITION) {
                const struct smu_sdbp_header *part;
                part = __smu_get_sdb_partition(hdr.cmd, NULL, 1);
                if (part == NULL)
                        return -EINVAL;
                else if (IS_ERR(part))
                        return PTR_ERR(part);
                return 0;
        } else if (hdr.cmdtype != SMU_CMDTYPE_SMU)
                return -EINVAL;
        else if (pp->mode != smu_file_commands)
                return -EBADFD;
        else if (hdr.data_len > SMU_MAX_DATA)
                return -EINVAL;

        spin_lock_irqsave(&pp->lock, flags);
        if (pp->busy) {
                spin_unlock_irqrestore(&pp->lock, flags);
                return -EBUSY;
        }
        pp->busy = 1;
        pp->cmd.status = 1;
        spin_unlock_irqrestore(&pp->lock, flags);

        if (copy_from_user(pp->buffer, buf + sizeof(hdr), hdr.data_len)) {
                pp->busy = 0;
                return -EFAULT;
        }

        pp->cmd.cmd = hdr.cmd;
        pp->cmd.data_len = hdr.data_len;
        pp->cmd.reply_len = SMU_MAX_DATA;
        pp->cmd.data_buf = pp->buffer;
        pp->cmd.reply_buf = pp->buffer;
        pp->cmd.done = smu_user_cmd_done;
        pp->cmd.misc = pp;
        rc = smu_queue_cmd(&pp->cmd);
        if (rc < 0)
                return rc;
        return count;
}


static ssize_t smu_read_command(struct file *file, struct smu_private *pp,
                                char __user *buf, size_t count)
{
        DECLARE_WAITQUEUE(wait, current);
        struct smu_user_reply_hdr hdr;
        unsigned long flags;
        int size, rc = 0;

        if (!pp->busy)
                return 0;
        if (count < sizeof(struct smu_user_reply_hdr))
                return -EOVERFLOW;
        spin_lock_irqsave(&pp->lock, flags);
        if (pp->cmd.status == 1) {
                if (file->f_flags & O_NONBLOCK) {
                        spin_unlock_irqrestore(&pp->lock, flags);
                        return -EAGAIN;
                }
                add_wait_queue(&pp->wait, &wait);
                for (;;) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        rc = 0;
                        if (pp->cmd.status != 1)
                                break;
                        rc = -ERESTARTSYS;
                        if (signal_pending(current))
                                break;
                        spin_unlock_irqrestore(&pp->lock, flags);
                        schedule();
                        spin_lock_irqsave(&pp->lock, flags);
                }
                set_current_state(TASK_RUNNING);
                remove_wait_queue(&pp->wait, &wait);
        }
        spin_unlock_irqrestore(&pp->lock, flags);
        if (rc)
                return rc;
        if (pp->cmd.status != 0)
                pp->cmd.reply_len = 0;
        size = sizeof(hdr) + pp->cmd.reply_len;
        if (count < size)
                size = count;
        rc = size;
        hdr.status = pp->cmd.status;
        hdr.reply_len = pp->cmd.reply_len;
        if (copy_to_user(buf, &hdr, sizeof(hdr)))
                return -EFAULT;
        size -= sizeof(hdr);
        if (size && copy_to_user(buf + sizeof(hdr), pp->buffer, size))
                return -EFAULT;
        pp->busy = 0;

        return rc;
}


static ssize_t smu_read_events(struct file *file, struct smu_private *pp,
                               char __user *buf, size_t count)
{
        /* Not implemented */
        msleep_interruptible(1000);
        return 0;
}


static ssize_t smu_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
{
        struct smu_private *pp = file->private_data;

        if (pp->mode == smu_file_commands)
                return smu_read_command(file, pp, buf, count);
        if (pp->mode == smu_file_events)
                return smu_read_events(file, pp, buf, count);

        return -EBADFD;
}

static unsigned int smu_fpoll(struct file *file, poll_table *wait)
{
        struct smu_private *pp = file->private_data;
        unsigned int mask = 0;
        unsigned long flags;

        if (pp == 0)
                return 0;

        if (pp->mode == smu_file_commands) {
                poll_wait(file, &pp->wait, wait);

                spin_lock_irqsave(&pp->lock, flags);
                if (pp->busy && pp->cmd.status != 1)
                        mask |= POLLIN;
                spin_unlock_irqrestore(&pp->lock, flags);
        } if (pp->mode == smu_file_events) {
                /* Not yet implemented */
        }
        return mask;
}

static int smu_release(struct inode *inode, struct file *file)
{
        struct smu_private *pp = file->private_data;
        unsigned long flags;
        unsigned int busy;

        if (pp == 0)
                return 0;

        file->private_data = NULL;

        /* Mark file as closing to avoid races with new request */
        spin_lock_irqsave(&pp->lock, flags);
        pp->mode = smu_file_closing;
        busy = pp->busy;

        /* Wait for any pending request to complete */
        if (busy && pp->cmd.status == 1) {
                DECLARE_WAITQUEUE(wait, current);

                add_wait_queue(&pp->wait, &wait);
                for (;;) {
                        set_current_state(TASK_UNINTERRUPTIBLE);
                        if (pp->cmd.status != 1)
                                break;
                        spin_unlock_irqrestore(&pp->lock, flags);
                        schedule();
                        spin_lock_irqsave(&pp->lock, flags);
                }
                set_current_state(TASK_RUNNING);
                remove_wait_queue(&pp->wait, &wait);
        }
        spin_unlock_irqrestore(&pp->lock, flags);

        spin_lock_irqsave(&smu_clist_lock, flags);
        list_del(&pp->list);
        spin_unlock_irqrestore(&smu_clist_lock, flags);
        kfree(pp);

        return 0;
}


static const struct file_operations smu_device_fops = {
        .llseek         = no_llseek,
        .read           = smu_read,
        .write          = smu_write,
        .poll           = smu_fpoll,
        .open           = smu_open,
        .release        = smu_release,
};

static struct miscdevice pmu_device = {
        MISC_DYNAMIC_MINOR, "smu", &smu_device_fops
};

static int smu_device_init(void)
{
        if (!smu)
                return -ENODEV;
        if (misc_register(&pmu_device) < 0)
                printk(KERN_ERR "via-pmu: cannot register misc device.\n");
        return 0;
}
device_initcall(smu_device_init);