smu.c

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/*
 * PowerMac G5 SMU driver
 *
 * Copyright 2004 J. Mayer <[email protected]>
 * 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: %02x %02x %02x %02x %02x %02x %02x %02x\n",
        ((u8 *)cmd->data_buf)[0], ((u8 *)cmd->data_buf)[1],
        ((u8 *)cmd->data_buf)[2], ((u8 *)cmd->data_buf)[3],
        ((u8 *)cmd->data_buf)[4], ((u8 *)cmd->data_buf)[5],
        ((u8 *)cmd->data_buf)[6], ((u8 *)cmd->data_buf)[7]);

    /* 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((unsigned long)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 (prom_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);