/*
 * arch/powerpc/platforms/powermac/low_i2c.c
 *
 *  Copyright (C) 2003-2005 Ben. Herrenschmidt (benh@kernel.crashing.org)
 *
 *  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.
 *
 * The linux i2c layer isn't completely suitable for our needs for various
 * reasons ranging from too late initialisation to semantics not perfectly
 * matching some requirements of the apple platform functions etc...
 *
 * This file thus provides a simple low level unified i2c interface for
 * powermac that covers the various types of i2c busses used in Apple machines.
 * For now, keywest, PMU and SMU, though we could add Cuda, or other bit
 * banging busses found on older chipstes in earlier machines if we ever need
 * one of them.
 *
 * The drivers in this file are synchronous/blocking. In addition, the
 * keywest one is fairly slow due to the use of msleep instead of interrupts
 * as the interrupt is currently used by i2c-keywest. In the long run, we
 * might want to get rid of those high-level interfaces to linux i2c layer
 * either completely (converting all drivers) or replacing them all with a
 * single stub driver on top of this one. Once done, the interrupt will be
 * available for our use.
 */

#undef DEBUG
#undef DEBUG_LOW

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/adb.h>
#include <linux/pmu.h>
#include <linux/delay.h>
#include <linux/completion.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/timer.h>
#include <linux/mutex.h>
#include <asm/keylargo.h>
#include <asm/uninorth.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/smu.h>
#include <asm/pmac_pfunc.h>
#include <asm/pmac_low_i2c.h>

#ifdef DEBUG
#define DBG(x...) do {\
                printk(KERN_DEBUG "low_i2c:" x);        \
        } while(0)
#else
#define DBG(x...)
#endif

#ifdef DEBUG_LOW
#define DBG_LOW(x...) do {\
                printk(KERN_DEBUG "low_i2c:" x);        \
        } while(0)
#else
#define DBG_LOW(x...)
#endif


static int pmac_i2c_force_poll = 1;

/*
 * A bus structure. Each bus in the system has such a structure associated.
 */
struct pmac_i2c_bus
{
        struct list_head        link;
        struct device_node      *controller;
        struct device_node      *busnode;
        int                     type;
        int                     flags;
        struct i2c_adapter      *adapter;
        void                    *hostdata;
        int                     channel;        /* some hosts have multiple */
        int                     mode;           /* current mode */
        struct mutex            mutex;
        int                     opened;
        int                     polled;         /* open mode */
        struct platform_device  *platform_dev;

        /* ops */
        int (*open)(struct pmac_i2c_bus *bus);
        void (*close)(struct pmac_i2c_bus *bus);
        int (*xfer)(struct pmac_i2c_bus *bus, u8 addrdir, int subsize,
                    u32 subaddr, u8 *data, int len);
};

static LIST_HEAD(pmac_i2c_busses);

/*
 * Keywest implementation
 */

struct pmac_i2c_host_kw
{
        struct mutex            mutex;          /* Access mutex for use by
                                                 * i2c-keywest */
        void __iomem            *base;          /* register base address */
        int                     bsteps;         /* register stepping */
        int                     speed;          /* speed */
        int                     irq;
        u8                      *data;
        unsigned                len;
        int                     state;
        int                     rw;
        int                     polled;
        int                     result;
        struct completion       complete;
        spinlock_t              lock;
        struct timer_list       timeout_timer;
};

/* Register indices */
typedef enum {
        reg_mode = 0,
        reg_control,
        reg_status,
        reg_isr,
        reg_ier,
        reg_addr,
        reg_subaddr,
        reg_data
} reg_t;

/* The Tumbler audio equalizer can be really slow sometimes */
#define KW_POLL_TIMEOUT         (2*HZ)

/* Mode register */
#define KW_I2C_MODE_100KHZ      0x00
#define KW_I2C_MODE_50KHZ       0x01
#define KW_I2C_MODE_25KHZ       0x02
#define KW_I2C_MODE_DUMB        0x00
#define KW_I2C_MODE_STANDARD    0x04
#define KW_I2C_MODE_STANDARDSUB 0x08
#define KW_I2C_MODE_COMBINED    0x0C
#define KW_I2C_MODE_MODE_MASK   0x0C
#define KW_I2C_MODE_CHAN_MASK   0xF0

/* Control register */
#define KW_I2C_CTL_AAK          0x01
#define KW_I2C_CTL_XADDR        0x02
#define KW_I2C_CTL_STOP         0x04
#define KW_I2C_CTL_START        0x08

/* Status register */
#define KW_I2C_STAT_BUSY        0x01
#define KW_I2C_STAT_LAST_AAK    0x02
#define KW_I2C_STAT_LAST_RW     0x04
#define KW_I2C_STAT_SDA         0x08
#define KW_I2C_STAT_SCL         0x10

/* IER & ISR registers */
#define KW_I2C_IRQ_DATA         0x01
#define KW_I2C_IRQ_ADDR         0x02
#define KW_I2C_IRQ_STOP         0x04
#define KW_I2C_IRQ_START        0x08
#define KW_I2C_IRQ_MASK         0x0F

/* State machine states */
enum {
        state_idle,
        state_addr,
        state_read,
        state_write,
        state_stop,
        state_dead
};

#define WRONG_STATE(name) do {\
                printk(KERN_DEBUG "KW: wrong state. Got %s, state: %s " \
                       "(isr: %02x)\n", \
                       name, __kw_state_names[host->state], isr); \
        } while(0)

static const char *__kw_state_names[] = {
        "state_idle",
        "state_addr",
        "state_read",
        "state_write",
        "state_stop",
        "state_dead"
};

static inline u8 __kw_read_reg(struct pmac_i2c_host_kw *host, reg_t reg)
{
        return readb(host->base + (((unsigned int)reg) << host->bsteps));
}

static inline void __kw_write_reg(struct pmac_i2c_host_kw *host,
                                  reg_t reg, u8 val)
{
        writeb(val, host->base + (((unsigned)reg) << host->bsteps));
        (void)__kw_read_reg(host, reg_subaddr);
}

#define kw_write_reg(reg, val)  __kw_write_reg(host, reg, val)
#define kw_read_reg(reg)        __kw_read_reg(host, reg)

static u8 kw_i2c_wait_interrupt(struct pmac_i2c_host_kw *host)
{
        int i, j;
        u8 isr;
        
        for (i = 0; i < 1000; i++) {
                isr = kw_read_reg(reg_isr) & KW_I2C_IRQ_MASK;
                if (isr != 0)
                        return isr;

                /* This code is used with the timebase frozen, we cannot rely
                 * on udelay nor schedule when in polled mode !
                 * For now, just use a bogus loop....
                 */
                if (host->polled) {
                        for (j = 1; j < 100000; j++)
                                mb();
                } else
                        msleep(1);
        }
        return isr;
}

static void kw_i2c_do_stop(struct pmac_i2c_host_kw *host, int result)
{
        kw_write_reg(reg_control, KW_I2C_CTL_STOP);
        host->state = state_stop;
        host->result = result;
}


static void kw_i2c_handle_interrupt(struct pmac_i2c_host_kw *host, u8 isr)
{
        u8 ack;

        DBG_LOW("kw_handle_interrupt(%s, isr: %x)\n",
                __kw_state_names[host->state], isr);

        if (host->state == state_idle) {
                printk(KERN_WARNING "low_i2c: Keywest got an out of state"
                       " interrupt, ignoring\n");
                kw_write_reg(reg_isr, isr);
                return;
        }

        if (isr == 0) {
                printk(KERN_WARNING "low_i2c: Timeout in i2c transfer"
                       " on keywest !\n");
                if (host->state != state_stop) {
                        kw_i2c_do_stop(host, -EIO);
                        return;
                }
                ack = kw_read_reg(reg_status);
                if (ack & KW_I2C_STAT_BUSY)
                        kw_write_reg(reg_status, 0);
                host->state = state_idle;
                kw_write_reg(reg_ier, 0x00);
                if (!host->polled)
                        complete(&host->complete);
                return;
        }

        if (isr & KW_I2C_IRQ_ADDR) {
                ack = kw_read_reg(reg_status);
                if (host->state != state_addr) {
                        WRONG_STATE("KW_I2C_IRQ_ADDR"); 
                        kw_i2c_do_stop(host, -EIO);
                }
                if ((ack & KW_I2C_STAT_LAST_AAK) == 0) {
                        host->result = -ENXIO;
                        host->state = state_stop;
                        DBG_LOW("KW: NAK on address\n");
                } else {
                        if (host->len == 0)
                                kw_i2c_do_stop(host, 0);
                        else if (host->rw) {
                                host->state = state_read;
                                if (host->len > 1)
                                        kw_write_reg(reg_control,
                                                     KW_I2C_CTL_AAK);
                        } else {
                                host->state = state_write;
                                kw_write_reg(reg_data, *(host->data++));
                                host->len--;
                        }
                }
                kw_write_reg(reg_isr, KW_I2C_IRQ_ADDR);
        }

        if (isr & KW_I2C_IRQ_DATA) {
                if (host->state == state_read) {
                        *(host->data++) = kw_read_reg(reg_data);
                        host->len--;
                        kw_write_reg(reg_isr, KW_I2C_IRQ_DATA);
                        if (host->len == 0)
                                host->state = state_stop;
                        else if (host->len == 1)
                                kw_write_reg(reg_control, 0);
                } else if (host->state == state_write) {
                        ack = kw_read_reg(reg_status);
                        if ((ack & KW_I2C_STAT_LAST_AAK) == 0) {
                                DBG_LOW("KW: nack on data write\n");
                                host->result = -EFBIG;
                                host->state = state_stop;
                        } else if (host->len) {
                                kw_write_reg(reg_data, *(host->data++));
                                host->len--;
                        } else
                                kw_i2c_do_stop(host, 0);
                } else {
                        WRONG_STATE("KW_I2C_IRQ_DATA"); 
                        if (host->state != state_stop)
                                kw_i2c_do_stop(host, -EIO);
                }
                kw_write_reg(reg_isr, KW_I2C_IRQ_DATA);
        }

        if (isr & KW_I2C_IRQ_STOP) {
                kw_write_reg(reg_isr, KW_I2C_IRQ_STOP);
                if (host->state != state_stop) {
                        WRONG_STATE("KW_I2C_IRQ_STOP");
                        host->result = -EIO;
                }
                host->state = state_idle;
                if (!host->polled)
                        complete(&host->complete);
        }

        /* Below should only happen in manual mode which we don't use ... */
        if (isr & KW_I2C_IRQ_START)
                kw_write_reg(reg_isr, KW_I2C_IRQ_START);

}

/* Interrupt handler */
static irqreturn_t kw_i2c_irq(int irq, void *dev_id)
{
        struct pmac_i2c_host_kw *host = dev_id;
        unsigned long flags;

        spin_lock_irqsave(&host->lock, flags);
        del_timer(&host->timeout_timer);
        kw_i2c_handle_interrupt(host, kw_read_reg(reg_isr));
        if (host->state != state_idle) {
                host->timeout_timer.expires = jiffies + KW_POLL_TIMEOUT;
                add_timer(&host->timeout_timer);
        }
        spin_unlock_irqrestore(&host->lock, flags);
        return IRQ_HANDLED;
}

static void kw_i2c_timeout(unsigned long data)
{
        struct pmac_i2c_host_kw *host = (struct pmac_i2c_host_kw *)data;
        unsigned long flags;

        spin_lock_irqsave(&host->lock, flags);
        kw_i2c_handle_interrupt(host, kw_read_reg(reg_isr));
        if (host->state != state_idle) {
                host->timeout_timer.expires = jiffies + KW_POLL_TIMEOUT;
                add_timer(&host->timeout_timer);
        }
        spin_unlock_irqrestore(&host->lock, flags);
}

static int kw_i2c_open(struct pmac_i2c_bus *bus)
{
        struct pmac_i2c_host_kw *host = bus->hostdata;
        mutex_lock(&host->mutex);
        return 0;
}

static void kw_i2c_close(struct pmac_i2c_bus *bus)
{
        struct pmac_i2c_host_kw *host = bus->hostdata;
        mutex_unlock(&host->mutex);
}

static int kw_i2c_xfer(struct pmac_i2c_bus *bus, u8 addrdir, int subsize,
                       u32 subaddr, u8 *data, int len)
{
        struct pmac_i2c_host_kw *host = bus->hostdata;
        u8 mode_reg = host->speed;
        int use_irq = host->irq != NO_IRQ && !bus->polled;

        /* Setup mode & subaddress if any */
        switch(bus->mode) {
        case pmac_i2c_mode_dumb:
                return -EINVAL;
        case pmac_i2c_mode_std:
                mode_reg |= KW_I2C_MODE_STANDARD;
                if (subsize != 0)
                        return -EINVAL;
                break;
        case pmac_i2c_mode_stdsub:
                mode_reg |= KW_I2C_MODE_STANDARDSUB;
                if (subsize != 1)
                        return -EINVAL;
                break;
        case pmac_i2c_mode_combined:
                mode_reg |= KW_I2C_MODE_COMBINED;
                if (subsize != 1)
                        return -EINVAL;
                break;
        }

        /* Setup channel & clear pending irqs */
        kw_write_reg(reg_isr, kw_read_reg(reg_isr));
        kw_write_reg(reg_mode, mode_reg | (bus->channel << 4));
        kw_write_reg(reg_status, 0);

        /* Set up address and r/w bit, strip possible stale bus number from
         * address top bits
         */
        kw_write_reg(reg_addr, addrdir & 0xff);

        /* Set up the sub address */
        if ((mode_reg & KW_I2C_MODE_MODE_MASK) == KW_I2C_MODE_STANDARDSUB
            || (mode_reg & KW_I2C_MODE_MODE_MASK) == KW_I2C_MODE_COMBINED)
                kw_write_reg(reg_subaddr, subaddr);

        /* Prepare for async operations */
        host->data = data;
        host->len = len;
        host->state = state_addr;
        host->result = 0;
        host->rw = (addrdir & 1);
        host->polled = bus->polled;

        /* Enable interrupt if not using polled mode and interrupt is
         * available
         */
        if (use_irq) {
                /* Clear completion */
                INIT_COMPLETION(host->complete);
                /* Ack stale interrupts */
                kw_write_reg(reg_isr, kw_read_reg(reg_isr));
                /* Arm timeout */
                host->timeout_timer.expires = jiffies + KW_POLL_TIMEOUT;
                add_timer(&host->timeout_timer);
                /* Enable emission */
                kw_write_reg(reg_ier, KW_I2C_IRQ_MASK);
        }

        /* Start sending address */
        kw_write_reg(reg_control, KW_I2C_CTL_XADDR);

        /* Wait for completion */
        if (use_irq)
                wait_for_completion(&host->complete);
        else {
                while(host->state != state_idle) {
                        unsigned long flags;

                        u8 isr = kw_i2c_wait_interrupt(host);
                        spin_lock_irqsave(&host->lock, flags);
                        kw_i2c_handle_interrupt(host, isr);
                        spin_unlock_irqrestore(&host->lock, flags);
                }
        }

        /* Disable emission */
        kw_write_reg(reg_ier, 0);

        return host->result;
}

static struct pmac_i2c_host_kw *__init kw_i2c_host_init(struct device_node *np)
{
        struct pmac_i2c_host_kw *host;
        const u32               *psteps, *prate, *addrp;
        u32                     steps;

        host = kzalloc(sizeof(struct pmac_i2c_host_kw), GFP_KERNEL);
        if (host == NULL) {
                printk(KERN_ERR "low_i2c: Can't allocate host for %s\n",
                       np->full_name);
                return NULL;
        }

        /* Apple is kind enough to provide a valid AAPL,address property
         * on all i2c keywest nodes so far ... we would have to fallback
         * to macio parsing if that wasn't the case
         */
        addrp = of_get_property(np, "AAPL,address", NULL);
        if (addrp == NULL) {
                printk(KERN_ERR "low_i2c: Can't find address for %s\n",
                       np->full_name);
                kfree(host);
                return NULL;
        }
        mutex_init(&host->mutex);
        init_completion(&host->complete);
        spin_lock_init(&host->lock);
        init_timer(&host->timeout_timer);
        host->timeout_timer.function = kw_i2c_timeout;
        host->timeout_timer.data = (unsigned long)host;

        psteps = of_get_property(np, "AAPL,address-step", NULL);
        steps = psteps ? (*psteps) : 0x10;
        for (host->bsteps = 0; (steps & 0x01) == 0; host->bsteps++)
                steps >>= 1;
        /* Select interface rate */
        host->speed = KW_I2C_MODE_25KHZ;
        prate = of_get_property(np, "AAPL,i2c-rate", NULL);
        if (prate) switch(*prate) {
        case 100:
                host->speed = KW_I2C_MODE_100KHZ;
                break;
        case 50:
                host->speed = KW_I2C_MODE_50KHZ;
                break;
        case 25:
                host->speed = KW_I2C_MODE_25KHZ;
                break;
        }       
        host->irq = irq_of_parse_and_map(np, 0);
        if (host->irq == NO_IRQ)
                printk(KERN_WARNING
                       "low_i2c: Failed to map interrupt for %s\n",
                       np->full_name);

        host->base = ioremap((*addrp), 0x1000);
        if (host->base == NULL) {
                printk(KERN_ERR "low_i2c: Can't map registers for %s\n",
                       np->full_name);
                kfree(host);
                return NULL;
        }

        /* Make sure IRQ is disabled */
        kw_write_reg(reg_ier, 0);

        /* Request chip interrupt */
        if (request_irq(host->irq, kw_i2c_irq, 0, "keywest i2c", host))
                host->irq = NO_IRQ;

        printk(KERN_INFO "KeyWest i2c @0x%08x irq %d %s\n",
               *addrp, host->irq, np->full_name);

        return host;
}


static void __init kw_i2c_add(struct pmac_i2c_host_kw *host,
                              struct device_node *controller,
                              struct device_node *busnode,
                              int channel)
{
        struct pmac_i2c_bus *bus;

        bus = kzalloc(sizeof(struct pmac_i2c_bus), GFP_KERNEL);
        if (bus == NULL)
                return;

        bus->controller = of_node_get(controller);
        bus->busnode = of_node_get(busnode);
        bus->type = pmac_i2c_bus_keywest;
        bus->hostdata = host;
        bus->channel = channel;
        bus->mode = pmac_i2c_mode_std;
        bus->open = kw_i2c_open;
        bus->close = kw_i2c_close;
        bus->xfer = kw_i2c_xfer;
        mutex_init(&bus->mutex);
        if (controller == busnode)
                bus->flags = pmac_i2c_multibus;
        list_add(&bus->link, &pmac_i2c_busses);

        printk(KERN_INFO " channel %d bus %s\n", channel,
               (controller == busnode) ? "<multibus>" : busnode->full_name);
}

static void __init kw_i2c_probe(void)
{
        struct device_node *np, *child, *parent;

        /* Probe keywest-i2c busses */
        for (np = NULL;
             (np = of_find_compatible_node(np, "i2c","keywest-i2c")) != NULL;){
                struct pmac_i2c_host_kw *host;
                int multibus, chans, i;

                /* Found one, init a host structure */
                host = kw_i2c_host_init(np);
                if (host == NULL)
                        continue;

                /* Now check if we have a multibus setup (old style) or if we
                 * have proper bus nodes. Note that the "new" way (proper bus
                 * nodes) might cause us to not create some busses that are
                 * kept hidden in the device-tree. In the future, we might
                 * want to work around that by creating busses without a node
                 * but not for now
                 */
                child = of_get_next_child(np, NULL);
                multibus = !child || strcmp(child->name, "i2c-bus");
                of_node_put(child);

                /* For a multibus setup, we get the bus count based on the
                 * parent type
                 */
                if (multibus) {
                        parent = of_get_parent(np);
                        if (parent == NULL)
                                continue;
                        chans = parent->name[0] == 'u' ? 2 : 1;
                        for (i = 0; i < chans; i++)
                                kw_i2c_add(host, np, np, i);
                } else {
                        for (child = NULL;
                             (child = of_get_next_child(np, child)) != NULL;) {
                                const u32 *reg = of_get_property(child,
                                                "reg", NULL);
                                if (reg == NULL)
                                        continue;
                                kw_i2c_add(host, np, child, *reg);
                        }
                }
        }
}


/*
 *
 * PMU implementation
 *
 */

#ifdef CONFIG_ADB_PMU

/*
 * i2c command block to the PMU
 */
struct pmu_i2c_hdr {
        u8      bus;
        u8      mode;
        u8      bus2;
        u8      address;
        u8      sub_addr;
        u8      comb_addr;
        u8      count;
        u8      data[];
};

static void pmu_i2c_complete(struct adb_request *req)
{
        complete(req->arg);
}

static int pmu_i2c_xfer(struct pmac_i2c_bus *bus, u8 addrdir, int subsize,
                        u32 subaddr, u8 *data, int len)
{
        struct adb_request *req = bus->hostdata;
        struct pmu_i2c_hdr *hdr = (struct pmu_i2c_hdr *)&req->data[1];
        struct completion comp;
        int read = addrdir & 1;
        int retry;
        int rc = 0;

        /* For now, limit ourselves to 16 bytes transfers */
        if (len > 16)
                return -EINVAL;

        init_completion(&comp);

        for (retry = 0; retry < 16; retry++) {
                memset(req, 0, sizeof(struct adb_request));
                hdr->bus = bus->channel;
                hdr->count = len;

                switch(bus->mode) {
                case pmac_i2c_mode_std:
                        if (subsize != 0)
                                return -EINVAL;
                        hdr->address = addrdir;
                        hdr->mode = PMU_I2C_MODE_SIMPLE;
                        break;
                case pmac_i2c_mode_stdsub:
                case pmac_i2c_mode_combined:
                        if (subsize != 1)
                                return -EINVAL;
                        hdr->address = addrdir & 0xfe;
                        hdr->comb_addr = addrdir;
                        hdr->sub_addr = subaddr;
                        if (bus->mode == pmac_i2c_mode_stdsub)
                                hdr->mode = PMU_I2C_MODE_STDSUB;
                        else
                                hdr->mode = PMU_I2C_MODE_COMBINED;
                        break;
                default:
                        return -EINVAL;
                }

                INIT_COMPLETION(comp);
                req->data[0] = PMU_I2C_CMD;
                req->reply[0] = 0xff;
                req->nbytes = sizeof(struct pmu_i2c_hdr) + 1;
                req->done = pmu_i2c_complete;
                req->arg = &comp;
                if (!read && len) {
                        memcpy(hdr->data, data, len);
                        req->nbytes += len;
                }
                rc = pmu_queue_request(req);
                if (rc)
                        return rc;
                wait_for_completion(&comp);
                if (req->reply[0] == PMU_I2C_STATUS_OK)
                        break;
                msleep(15);
        }
        if (req->reply[0] != PMU_I2C_STATUS_OK)
                return -EIO;

        for (retry = 0; retry < 16; retry++) {
                memset(req, 0, sizeof(struct adb_request));

                /* I know that looks like a lot, slow as hell, but darwin
                 * does it so let's be on the safe side for now
                 */
                msleep(15);

                hdr->bus = PMU_I2C_BUS_STATUS;

                INIT_COMPLETION(comp);
                req->data[0] = PMU_I2C_CMD;
                req->reply[0] = 0xff;
                req->nbytes = 2;
                req->done = pmu_i2c_complete;
                req->arg = &comp;
                rc = pmu_queue_request(req);
                if (rc)
                        return rc;
                wait_for_completion(&comp);

                if (req->reply[0] == PMU_I2C_STATUS_OK && !read)
                        return 0;
                if (req->reply[0] == PMU_I2C_STATUS_DATAREAD && read) {
                        int rlen = req->reply_len - 1;

                        if (rlen != len) {
                                printk(KERN_WARNING "low_i2c: PMU returned %d"
                                       " bytes, expected %d !\n", rlen, len);
                                return -EIO;
                        }
                        if (len)
                                memcpy(data, &req->reply[1], len);
                        return 0;
                }
        }
        return -EIO;
}

static void __init pmu_i2c_probe(void)
{
        struct pmac_i2c_bus *bus;
        struct device_node *busnode;
        int channel, sz;

        if (!pmu_present())
                return;

        /* There might or might not be a "pmu-i2c" node, we use that
         * or via-pmu itself, whatever we find. I haven't seen a machine
         * with separate bus nodes, so we assume a multibus setup
         */
        busnode = of_find_node_by_name(NULL, "pmu-i2c");
        if (busnode == NULL)
                busnode = of_find_node_by_name(NULL, "via-pmu");
        if (busnode == NULL)
                return;

        printk(KERN_INFO "PMU i2c %s\n", busnode->full_name);

        /*
         * We add bus 1 and 2 only for now, bus 0 is "special"
         */
        for (channel = 1; channel <= 2; channel++) {
                sz = sizeof(struct pmac_i2c_bus) + sizeof(struct adb_request);
                bus = kzalloc(sz, GFP_KERNEL);
                if (bus == NULL)
                        return;

                bus->controller = busnode;
                bus->busnode = busnode;
                bus->type = pmac_i2c_bus_pmu;
                bus->channel = channel;
                bus->mode = pmac_i2c_mode_std;
                bus->hostdata = bus + 1;
                bus->xfer = pmu_i2c_xfer;
                mutex_init(&bus->mutex);
                bus->flags = pmac_i2c_multibus;
                list_add(&bus->link, &pmac_i2c_busses);

                printk(KERN_INFO " channel %d bus <multibus>\n", channel);
        }
}

#endif /* CONFIG_ADB_PMU */


/*
 *
 * SMU implementation
 *
 */

#ifdef CONFIG_PMAC_SMU

static void smu_i2c_complete(struct smu_i2c_cmd *cmd, void *misc)
{
        complete(misc);
}

static int smu_i2c_xfer(struct pmac_i2c_bus *bus, u8 addrdir, int subsize,
                        u32 subaddr, u8 *data, int len)
{
        struct smu_i2c_cmd *cmd = bus->hostdata;
        struct completion comp;
        int read = addrdir & 1;
        int rc = 0;

        if ((read && len > SMU_I2C_READ_MAX) ||
            ((!read) && len > SMU_I2C_WRITE_MAX))
                return -EINVAL;

        memset(cmd, 0, sizeof(struct smu_i2c_cmd));
        cmd->info.bus = bus->channel;
        cmd->info.devaddr = addrdir;
        cmd->info.datalen = len;

        switch(bus->mode) {
        case pmac_i2c_mode_std:
                if (subsize != 0)
                        return -EINVAL;
                cmd->info.type = SMU_I2C_TRANSFER_SIMPLE;
                break;
        case pmac_i2c_mode_stdsub:
        case pmac_i2c_mode_combined:
                if (subsize > 3 || subsize < 1)
                        return -EINVAL;
                cmd->info.sublen = subsize;
                /* that's big-endian only but heh ! */
                memcpy(&cmd->info.subaddr, ((char *)&subaddr) + (4 - subsize),
                       subsize);
                if (bus->mode == pmac_i2c_mode_stdsub)
                        cmd->info.type = SMU_I2C_TRANSFER_STDSUB;
                else
                        cmd->info.type = SMU_I2C_TRANSFER_COMBINED;
                break;
        default:
                return -EINVAL;
        }
        if (!read && len)
                memcpy(cmd->info.data, data, len);

        init_completion(&comp);
        cmd->done = smu_i2c_complete;
        cmd->misc = &comp;
        rc = smu_queue_i2c(cmd);
        if (rc < 0)
                return rc;
        wait_for_completion(&comp);
        rc = cmd->status;

        if (read && len)
                memcpy(data, cmd->info.data, len);
        return rc < 0 ? rc : 0;
}

static void __init smu_i2c_probe(void)
{
        struct device_node *controller, *busnode;
        struct pmac_i2c_bus *bus;
        const u32 *reg;
        int sz;

        if (!smu_present())
                return;

        controller = of_find_node_by_name(NULL, "smu-i2c-control");
        if (controller == NULL)
                controller = of_find_node_by_name(NULL, "smu");
        if (controller == NULL)
                return;

        printk(KERN_INFO "SMU i2c %s\n", controller->full_name);

        /* Look for childs, note that they might not be of the right
         * type as older device trees mix i2c busses and other thigns
         * at the same level
         */
        for (busnode = NULL;
             (busnode = of_get_next_child(controller, busnode)) != NULL;) {
                if (strcmp(busnode->type, "i2c") &&
                    strcmp(busnode->type, "i2c-bus"))
                        continue;
                reg = of_get_property(busnode, "reg", NULL);
                if (reg == NULL)
                        continue;

                sz = sizeof(struct pmac_i2c_bus) + sizeof(struct smu_i2c_cmd);
                bus = kzalloc(sz, GFP_KERNEL);
                if (bus == NULL)
                        return;

                bus->controller = controller;
                bus->busnode = of_node_get(busnode);
                bus->type = pmac_i2c_bus_smu;
                bus->channel = *reg;
                bus->mode = pmac_i2c_mode_std;
                bus->hostdata = bus + 1;
                bus->xfer = smu_i2c_xfer;
                mutex_init(&bus->mutex);
                bus->flags = 0;
                list_add(&bus->link, &pmac_i2c_busses);

                printk(KERN_INFO " channel %x bus %s\n",
                       bus->channel, busnode->full_name);
        }
}

#endif /* CONFIG_PMAC_SMU */

/*
 *
 * Core code
 *
 */


struct pmac_i2c_bus *pmac_i2c_find_bus(struct device_node *node)
{
        struct device_node *p = of_node_get(node);
        struct device_node *prev = NULL;
        struct pmac_i2c_bus *bus;

        while(p) {
                list_for_each_entry(bus, &pmac_i2c_busses, link) {
                        if (p == bus->busnode) {
                                if (prev && bus->flags & pmac_i2c_multibus) {
                                        const u32 *reg;
                                        reg = of_get_property(prev, "reg",
                                                                NULL);
                                        if (!reg)
                                                continue;
                                        if (((*reg) >> 8) != bus->channel)
                                                continue;
                                }
                                of_node_put(p);
                                of_node_put(prev);
                                return bus;
                        }
                }
                of_node_put(prev);
                prev = p;
                p = of_get_parent(p);
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(pmac_i2c_find_bus);

u8 pmac_i2c_get_dev_addr(struct device_node *device)
{
        const u32 *reg = of_get_property(device, "reg", NULL);

        if (reg == NULL)
                return 0;

        return (*reg) & 0xff;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_dev_addr);

struct device_node *pmac_i2c_get_controller(struct pmac_i2c_bus *bus)
{
        return bus->controller;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_controller);

struct device_node *pmac_i2c_get_bus_node(struct pmac_i2c_bus *bus)
{
        return bus->busnode;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_bus_node);

int pmac_i2c_get_type(struct pmac_i2c_bus *bus)
{
        return bus->type;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_type);

int pmac_i2c_get_flags(struct pmac_i2c_bus *bus)
{
        return bus->flags;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_flags);

int pmac_i2c_get_channel(struct pmac_i2c_bus *bus)
{
        return bus->channel;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_channel);


void pmac_i2c_attach_adapter(struct pmac_i2c_bus *bus,
                             struct i2c_adapter *adapter)
{
        WARN_ON(bus->adapter != NULL);
        bus->adapter = adapter;
}
EXPORT_SYMBOL_GPL(pmac_i2c_attach_adapter);

void pmac_i2c_detach_adapter(struct pmac_i2c_bus *bus,
                             struct i2c_adapter *adapter)
{
        WARN_ON(bus->adapter != adapter);
        bus->adapter = NULL;
}
EXPORT_SYMBOL_GPL(pmac_i2c_detach_adapter);

struct i2c_adapter *pmac_i2c_get_adapter(struct pmac_i2c_bus *bus)
{
        return bus->adapter;
}
EXPORT_SYMBOL_GPL(pmac_i2c_get_adapter);

struct pmac_i2c_bus *pmac_i2c_adapter_to_bus(struct i2c_adapter *adapter)
{
        struct pmac_i2c_bus *bus;

        list_for_each_entry(bus, &pmac_i2c_busses, link)
                if (bus->adapter == adapter)
                        return bus;
        return NULL;
}
EXPORT_SYMBOL_GPL(pmac_i2c_adapter_to_bus);

int pmac_i2c_match_adapter(struct device_node *dev, struct i2c_adapter *adapter)
{
        struct pmac_i2c_bus *bus = pmac_i2c_find_bus(dev);

        if (bus == NULL)
                return 0;
        return (bus->adapter == adapter);
}
EXPORT_SYMBOL_GPL(pmac_i2c_match_adapter);

int pmac_low_i2c_lock(struct device_node *np)
{
        struct pmac_i2c_bus *bus, *found = NULL;

        list_for_each_entry(bus, &pmac_i2c_busses, link) {
                if (np == bus->controller) {
                        found = bus;
                        break;
                }
        }
        if (!found)
                return -ENODEV;
        return pmac_i2c_open(bus, 0);
}
EXPORT_SYMBOL_GPL(pmac_low_i2c_lock);

int pmac_low_i2c_unlock(struct device_node *np)
{
        struct pmac_i2c_bus *bus, *found = NULL;

        list_for_each_entry(bus, &pmac_i2c_busses, link) {
                if (np == bus->controller) {
                        found = bus;
                        break;
                }
        }
        if (!found)
                return -ENODEV;
        pmac_i2c_close(bus);
        return 0;
}
EXPORT_SYMBOL_GPL(pmac_low_i2c_unlock);


int pmac_i2c_open(struct pmac_i2c_bus *bus, int polled)
{
        int rc;

        mutex_lock(&bus->mutex);
        bus->polled = polled || pmac_i2c_force_poll;
        bus->opened = 1;
        bus->mode = pmac_i2c_mode_std;
        if (bus->open && (rc = bus->open(bus)) != 0) {
                bus->opened = 0;
                mutex_unlock(&bus->mutex);
                return rc;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(pmac_i2c_open);

void pmac_i2c_close(struct pmac_i2c_bus *bus)
{
        WARN_ON(!bus->opened);
        if (bus->close)
                bus->close(bus);
        bus->opened = 0;
        mutex_unlock(&bus->mutex);
}
EXPORT_SYMBOL_GPL(pmac_i2c_close);

int pmac_i2c_setmode(struct pmac_i2c_bus *bus, int mode)
{
        WARN_ON(!bus->opened);

        /* Report me if you see the error below as there might be a new
         * "combined4" mode that I need to implement for the SMU bus
         */
        if (mode < pmac_i2c_mode_dumb || mode > pmac_i2c_mode_combined) {
                printk(KERN_ERR "low_i2c: Invalid mode %d requested on"
                       " bus %s !\n", mode, bus->busnode->full_name);
                return -EINVAL;
        }
        bus->mode = mode;

        return 0;
}
EXPORT_SYMBOL_GPL(pmac_i2c_setmode);

int pmac_i2c_xfer(struct pmac_i2c_bus *bus, u8 addrdir, int subsize,
                  u32 subaddr, u8 *data, int len)
{
        int rc;

        WARN_ON(!bus->opened);

        DBG("xfer() chan=%d, addrdir=0x%x, mode=%d, subsize=%d, subaddr=0x%x,"
            " %d bytes, bus %s\n", bus->channel, addrdir, bus->mode, subsize,
            subaddr, len, bus->busnode->full_name);

        rc = bus->xfer(bus, addrdir, subsize, subaddr, data, len);

#ifdef DEBUG
        if (rc)
                DBG("xfer error %d\n", rc);
#endif
        return rc;
}
EXPORT_SYMBOL_GPL(pmac_i2c_xfer);

/* some quirks for platform function decoding */
enum {
        pmac_i2c_quirk_invmask = 0x00000001u,
        pmac_i2c_quirk_skip = 0x00000002u,
};

static void pmac_i2c_devscan(void (*callback)(struct device_node *dev,
                                              int quirks))
{
        struct pmac_i2c_bus *bus;
        struct device_node *np;
        static struct whitelist_ent {
                char *name;
                char *compatible;
                int quirks;
        } whitelist[] = {
                /* XXX Study device-tree's & apple drivers are get the quirks
                 * right !
                 */
                /* Workaround: It seems that running the clockspreading
                 * properties on the eMac will cause lockups during boot.
                 * The machine seems to work fine without that. So for now,
                 * let's make sure i2c-hwclock doesn't match about "imic"
                 * clocks and we'll figure out if we really need to do
                 * something special about those later.
                 */
                { "i2c-hwclock", "imic5002", pmac_i2c_quirk_skip },
                { "i2c-hwclock", "imic5003", pmac_i2c_quirk_skip },
                { "i2c-hwclock", NULL, pmac_i2c_quirk_invmask },
                { "i2c-cpu-voltage", NULL, 0},
                {  "temp-monitor", NULL, 0 },
                {  "supply-monitor", NULL, 0 },
                { NULL, NULL, 0 },
        };

        /* Only some devices need to have platform functions instanciated
         * here. For now, we have a table. Others, like 9554 i2c GPIOs used
         * on Xserve, if we ever do a driver for them, will use their own
         * platform function instance
         */
        list_for_each_entry(bus, &pmac_i2c_busses, link) {
                for (np = NULL;
                     (np = of_get_next_child(bus->busnode, np)) != NULL;) {
                        struct whitelist_ent *p;
                        /* If multibus, check if device is on that bus */
                        if (bus->flags & pmac_i2c_multibus)
                                if (bus != pmac_i2c_find_bus(np))
                                        continue;
                        for (p = whitelist; p->name != NULL; p++) {
                                if (strcmp(np->name, p->name))
                                        continue;
                                if (p->compatible &&
                                    !of_device_is_compatible(np, p->compatible))
                                        continue;
                                if (p->quirks & pmac_i2c_quirk_skip)
                                        break;
                                callback(np, p->quirks);
                                break;
                        }
                }
        }
}

#define MAX_I2C_DATA    64

struct pmac_i2c_pf_inst
{
        struct pmac_i2c_bus     *bus;
        u8                      addr;
        u8                      buffer[MAX_I2C_DATA];
        u8                      scratch[MAX_I2C_DATA];
        int                     bytes;
        int                     quirks;
};

static void* pmac_i2c_do_begin(struct pmf_function *func, struct pmf_args *args)
{
        struct pmac_i2c_pf_inst *inst;
        struct pmac_i2c_bus     *bus;

        bus = pmac_i2c_find_bus(func->node);
        if (bus == NULL) {
                printk(KERN_ERR "low_i2c: Can't find bus for %s (pfunc)\n",
                       func->node->full_name);
                return NULL;
        }
        if (pmac_i2c_open(bus, 0)) {
                printk(KERN_ERR "low_i2c: Can't open i2c bus for %s (pfunc)\n",
                       func->node->full_name);
                return NULL;
        }

        /* XXX might need GFP_ATOMIC when called during the suspend process,
         * but then, there are already lots of issues with suspending when
         * near OOM that need to be resolved, the allocator itself should
         * probably make GFP_NOIO implicit during suspend
         */
        inst = kzalloc(sizeof(struct pmac_i2c_pf_inst), GFP_KERNEL);
        if (inst == NULL) {
                pmac_i2c_close(bus);
                return NULL;
        }
        inst->bus = bus;
        inst->addr = pmac_i2c_get_dev_addr(func->node);
        inst->quirks = (int)(long)func->driver_data;
        return inst;
}

static void pmac_i2c_do_end(struct pmf_function *func, void *instdata)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        if (inst == NULL)
                return;
        pmac_i2c_close(inst->bus);
        if (inst)
                kfree(inst);
}

static int pmac_i2c_do_read(PMF_STD_ARGS, u32 len)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        inst->bytes = len;
        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_read, 0, 0,
                             inst->buffer, len);
}

static int pmac_i2c_do_write(PMF_STD_ARGS, u32 len, const u8 *data)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_write, 0, 0,
                             (u8 *)data, len);
}

/* This function is used to do the masking & OR'ing for the "rmw" type
 * callbacks. Ze should apply the mask and OR in the values in the
 * buffer before writing back. The problem is that it seems that
 * various darwin drivers implement the mask/or differently, thus
 * we need to check the quirks first
 */
static void pmac_i2c_do_apply_rmw(struct pmac_i2c_pf_inst *inst,
                                  u32 len, const u8 *mask, const u8 *val)
{
        int i;

        if (inst->quirks & pmac_i2c_quirk_invmask) {
                for (i = 0; i < len; i ++)
                        inst->scratch[i] = (inst->buffer[i] & mask[i]) | val[i];
        } else {
                for (i = 0; i < len; i ++)
                        inst->scratch[i] = (inst->buffer[i] & ~mask[i])
                                | (val[i] & mask[i]);
        }
}

static int pmac_i2c_do_rmw(PMF_STD_ARGS, u32 masklen, u32 valuelen,
                           u32 totallen, const u8 *maskdata,
                           const u8 *valuedata)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        if (masklen > inst->bytes || valuelen > inst->bytes ||
            totallen > inst->bytes || valuelen > masklen)
                return -EINVAL;

        pmac_i2c_do_apply_rmw(inst, masklen, maskdata, valuedata);

        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_write, 0, 0,
                             inst->scratch, totallen);
}

static int pmac_i2c_do_read_sub(PMF_STD_ARGS, u8 subaddr, u32 len)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        inst->bytes = len;
        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_read, 1, subaddr,
                             inst->buffer, len);
}

static int pmac_i2c_do_write_sub(PMF_STD_ARGS, u8 subaddr, u32 len,
                                     const u8 *data)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_write, 1,
                             subaddr, (u8 *)data, len);
}

static int pmac_i2c_do_set_mode(PMF_STD_ARGS, int mode)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        return pmac_i2c_setmode(inst->bus, mode);
}

static int pmac_i2c_do_rmw_sub(PMF_STD_ARGS, u8 subaddr, u32 masklen,
                               u32 valuelen, u32 totallen, const u8 *maskdata,
                               const u8 *valuedata)
{
        struct pmac_i2c_pf_inst *inst = instdata;

        if (masklen > inst->bytes || valuelen > inst->bytes ||
            totallen > inst->bytes || valuelen > masklen)
                return -EINVAL;

        pmac_i2c_do_apply_rmw(inst, masklen, maskdata, valuedata);

        return pmac_i2c_xfer(inst->bus, inst->addr | pmac_i2c_write, 1,
                             subaddr, inst->scratch, totallen);
}

static int pmac_i2c_do_mask_and_comp(PMF_STD_ARGS, u32 len,
                                     const u8 *maskdata,
                                     const u8 *valuedata)
{
        struct pmac_i2c_pf_inst *inst = instdata;
        int i, match;

        /* Get return value pointer, it's assumed to be a u32 */
        if (!args || !args->count || !args->u[0].p)
                return -EINVAL;

        /* Check buffer */
        if (len > inst->bytes)
                return -EINVAL;

        for (i = 0, match = 1; match && i < len; i ++)
                if ((inst->buffer[i] & maskdata[i]) != valuedata[i])
                        match = 0;
        *args->u[0].p = match;
        return 0;
}

static int pmac_i2c_do_delay(PMF_STD_ARGS, u32 duration)
{
        msleep((duration + 999) / 1000);
        return 0;
}


static struct pmf_handlers pmac_i2c_pfunc_handlers = {
        .begin                  = pmac_i2c_do_begin,
        .end                    = pmac_i2c_do_end,
        .read_i2c               = pmac_i2c_do_read,
        .write_i2c              = pmac_i2c_do_write,
        .rmw_i2c                = pmac_i2c_do_rmw,
        .read_i2c_sub           = pmac_i2c_do_read_sub,
        .write_i2c_sub          = pmac_i2c_do_write_sub,
        .rmw_i2c_sub            = pmac_i2c_do_rmw_sub,
        .set_i2c_mode           = pmac_i2c_do_set_mode,
        .mask_and_compare       = pmac_i2c_do_mask_and_comp,
        .delay                  = pmac_i2c_do_delay,
};

static void __init pmac_i2c_dev_create(struct device_node *np, int quirks)
{
        DBG("dev_create(%s)\n", np->full_name);

        pmf_register_driver(np, &pmac_i2c_pfunc_handlers,
                            (void *)(long)quirks);
}

static void __init pmac_i2c_dev_init(struct device_node *np, int quirks)
{
        DBG("dev_create(%s)\n", np->full_name);

        pmf_do_functions(np, NULL, 0, PMF_FLAGS_ON_INIT, NULL);
}

static void pmac_i2c_dev_suspend(struct device_node *np, int quirks)
{
        DBG("dev_suspend(%s)\n", np->full_name);
        pmf_do_functions(np, NULL, 0, PMF_FLAGS_ON_SLEEP, NULL);
}

static void pmac_i2c_dev_resume(struct device_node *np, int quirks)
{
        DBG("dev_resume(%s)\n", np->full_name);
        pmf_do_functions(np, NULL, 0, PMF_FLAGS_ON_WAKE, NULL);
}

void pmac_pfunc_i2c_suspend(void)
{
        pmac_i2c_devscan(pmac_i2c_dev_suspend);
}

void pmac_pfunc_i2c_resume(void)
{
        pmac_i2c_devscan(pmac_i2c_dev_resume);
}

/*
 * Initialize us: probe all i2c busses on the machine, instantiate
 * busses and platform functions as needed.
 */
/* This is non-static as it might be called early by smp code */
int __init pmac_i2c_init(void)
{
        static int i2c_inited;

        if (i2c_inited)
                return 0;
        i2c_inited = 1;

        if (!machine_is(powermac))
                return 0;

        /* Probe keywest-i2c busses */
        kw_i2c_probe();

#ifdef CONFIG_ADB_PMU
        /* Probe PMU i2c busses */
        pmu_i2c_probe();
#endif

#ifdef CONFIG_PMAC_SMU
        /* Probe SMU i2c busses */
        smu_i2c_probe();
#endif

        /* Now add plaform functions for some known devices */
        pmac_i2c_devscan(pmac_i2c_dev_create);

        return 0;
}
arch_initcall(pmac_i2c_init);

/* Since pmac_i2c_init can be called too early for the platform device
 * registration, we need to do it at a later time. In our case, subsys
 * happens to fit well, though I agree it's a bit of a hack...
 */
static int __init pmac_i2c_create_platform_devices(void)
{
        struct pmac_i2c_bus *bus;
        int i = 0;

        /* In the case where we are initialized from smp_init(), we must
         * not use the timer (and thus the irq). It's safe from now on
         * though
         */
        pmac_i2c_force_poll = 0;

        /* Create platform devices */
        list_for_each_entry(bus, &pmac_i2c_busses, link) {
                bus->platform_dev =
                        platform_device_alloc("i2c-powermac", i++);
                if (bus->platform_dev == NULL)
                        return -ENOMEM;
                bus->platform_dev->dev.platform_data = bus;
                platform_device_add(bus->platform_dev);
        }

        /* Now call platform "init" functions */
        pmac_i2c_devscan(pmac_i2c_dev_init);

        return 0;
}
subsys_initcall(pmac_i2c_create_platform_devices);