/*
 * HP i8042-based System Device Controller driver.
 *
 * Copyright (c) 2001 Brian S. Julin
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL").
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *
 * References:
 * System Device Controller Microprocessor Firmware Theory of Operation
 *      for Part Number 1820-4784 Revision B.  Dwg No. A-1820-4784-2
 * Helge Deller's original hilkbd.c port for PA-RISC.
 *
 *
 * Driver theory of operation:
 *
 * hp_sdc_put does all writing to the SDC.  ISR can run on a different
 * CPU than hp_sdc_put, but only one CPU runs hp_sdc_put at a time
 * (it cannot really benefit from SMP anyway.)  A tasket fit this perfectly.
 *
 * All data coming back from the SDC is sent via interrupt and can be read
 * fully in the ISR, so there are no latency/throughput problems there.
 * The problem is with output, due to the slow clock speed of the SDC
 * compared to the CPU.  This should not be too horrible most of the time,
 * but if used with HIL devices that support the multibyte transfer command,
 * keeping outbound throughput flowing at the 6500KBps that the HIL is
 * capable of is more than can be done at HZ=100.
 *
 * Busy polling for IBF clear wastes CPU cycles and bus cycles.  hp_sdc.ibf
 * is set to 0 when the IBF flag in the status register has cleared.  ISR
 * may do this, and may also access the parts of queued transactions related
 * to reading data back from the SDC, but otherwise will not touch the
 * hp_sdc state. Whenever a register is written hp_sdc.ibf is set to 1.
 *
 * The i8042 write index and the values in the 4-byte input buffer
 * starting at 0x70 are kept track of in hp_sdc.wi, and .r7[], respectively,
 * to minimize the amount of IO needed to the SDC.  However these values
 * do not need to be locked since they are only ever accessed by hp_sdc_put.
 *
 * A timer task schedules the tasklet once per second just to make
 * sure it doesn't freeze up and to allow for bad reads to time out.
 */

#include <linux/hp_sdc.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/time.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/hil.h>
#include <asm/io.h>
#include <asm/system.h>

/* Machine-specific abstraction */

#if defined(__hppa__)
# include <asm/parisc-device.h>
# define sdc_readb(p)           gsc_readb(p)
# define sdc_writeb(v,p)        gsc_writeb((v),(p))
#elif defined(__mc68000__)
# include <asm/uaccess.h>
# define sdc_readb(p)           in_8(p)
# define sdc_writeb(v,p)        out_8((p),(v))
#else
# error "HIL is not supported on this platform"
#endif

#define PREFIX "HP SDC: "

MODULE_AUTHOR("Brian S. Julin <bri@calyx.com>");
MODULE_DESCRIPTION("HP i8042-based SDC Driver");
MODULE_LICENSE("Dual BSD/GPL");

EXPORT_SYMBOL(hp_sdc_request_timer_irq);
EXPORT_SYMBOL(hp_sdc_request_hil_irq);
EXPORT_SYMBOL(hp_sdc_request_cooked_irq);

EXPORT_SYMBOL(hp_sdc_release_timer_irq);
EXPORT_SYMBOL(hp_sdc_release_hil_irq);
EXPORT_SYMBOL(hp_sdc_release_cooked_irq);

EXPORT_SYMBOL(__hp_sdc_enqueue_transaction);
EXPORT_SYMBOL(hp_sdc_enqueue_transaction);
EXPORT_SYMBOL(hp_sdc_dequeue_transaction);

static unsigned int hp_sdc_disabled;
module_param_named(no_hpsdc, hp_sdc_disabled, bool, 0);
MODULE_PARM_DESC(no_hpsdc, "Do not enable HP SDC driver.");

static hp_i8042_sdc     hp_sdc; /* All driver state is kept in here. */

/*************** primitives for use in any context *********************/
static inline uint8_t hp_sdc_status_in8(void)
{
        uint8_t status;
        unsigned long flags;

        write_lock_irqsave(&hp_sdc.ibf_lock, flags);
        status = sdc_readb(hp_sdc.status_io);
        if (!(status & HP_SDC_STATUS_IBF))
                hp_sdc.ibf = 0;
        write_unlock_irqrestore(&hp_sdc.ibf_lock, flags);

        return status;
}

static inline uint8_t hp_sdc_data_in8(void)
{
        return sdc_readb(hp_sdc.data_io);
}

static inline void hp_sdc_status_out8(uint8_t val)
{
        unsigned long flags;

        write_lock_irqsave(&hp_sdc.ibf_lock, flags);
        hp_sdc.ibf = 1;
        if ((val & 0xf0) == 0xe0)
                hp_sdc.wi = 0xff;
        sdc_writeb(val, hp_sdc.status_io);
        write_unlock_irqrestore(&hp_sdc.ibf_lock, flags);
}

static inline void hp_sdc_data_out8(uint8_t val)
{
        unsigned long flags;

        write_lock_irqsave(&hp_sdc.ibf_lock, flags);
        hp_sdc.ibf = 1;
        sdc_writeb(val, hp_sdc.data_io);
        write_unlock_irqrestore(&hp_sdc.ibf_lock, flags);
}

/*      Care must be taken to only invoke hp_sdc_spin_ibf when
 *      absolutely needed, or in rarely invoked subroutines.
 *      Not only does it waste CPU cycles, it also wastes bus cycles.
 */
static inline void hp_sdc_spin_ibf(void)
{
        unsigned long flags;
        rwlock_t *lock;

        lock = &hp_sdc.ibf_lock;

        read_lock_irqsave(lock, flags);
        if (!hp_sdc.ibf) {
                read_unlock_irqrestore(lock, flags);
                return;
        }
        read_unlock(lock);
        write_lock(lock);
        while (sdc_readb(hp_sdc.status_io) & HP_SDC_STATUS_IBF)
                { }
        hp_sdc.ibf = 0;
        write_unlock_irqrestore(lock, flags);
}


/************************ Interrupt context functions ************************/
static void hp_sdc_take(int irq, void *dev_id, uint8_t status, uint8_t data)
{
        hp_sdc_transaction *curr;

        read_lock(&hp_sdc.rtq_lock);
        if (hp_sdc.rcurr < 0) {
                read_unlock(&hp_sdc.rtq_lock);
                return;
        }
        curr = hp_sdc.tq[hp_sdc.rcurr];
        read_unlock(&hp_sdc.rtq_lock);

        curr->seq[curr->idx++] = status;
        curr->seq[curr->idx++] = data;
        hp_sdc.rqty -= 2;
        do_gettimeofday(&hp_sdc.rtv);

        if (hp_sdc.rqty <= 0) {
                /* All data has been gathered. */
                if (curr->seq[curr->actidx] & HP_SDC_ACT_SEMAPHORE)
                        if (curr->act.semaphore)
                                up(curr->act.semaphore);

                if (curr->seq[curr->actidx] & HP_SDC_ACT_CALLBACK)
                        if (curr->act.irqhook)
                                curr->act.irqhook(irq, dev_id, status, data);

                curr->actidx = curr->idx;
                curr->idx++;
                /* Return control of this transaction */
                write_lock(&hp_sdc.rtq_lock);
                hp_sdc.rcurr = -1;
                hp_sdc.rqty = 0;
                write_unlock(&hp_sdc.rtq_lock);
                tasklet_schedule(&hp_sdc.task);
        }
}

static irqreturn_t hp_sdc_isr(int irq, void *dev_id)
{
        uint8_t status, data;

        status = hp_sdc_status_in8();
        /* Read data unconditionally to advance i8042. */
        data =   hp_sdc_data_in8();

        /* For now we are ignoring these until we get the SDC to behave. */
        if (((status & 0xf1) == 0x51) && data == 0x82)
                return IRQ_HANDLED;

        switch (status & HP_SDC_STATUS_IRQMASK) {
        case 0: /* This case is not documented. */
                break;

        case HP_SDC_STATUS_USERTIMER:
        case HP_SDC_STATUS_PERIODIC:
        case HP_SDC_STATUS_TIMER:
                read_lock(&hp_sdc.hook_lock);
                if (hp_sdc.timer != NULL)
                        hp_sdc.timer(irq, dev_id, status, data);
                read_unlock(&hp_sdc.hook_lock);
                break;

        case HP_SDC_STATUS_REG:
                hp_sdc_take(irq, dev_id, status, data);
                break;

        case HP_SDC_STATUS_HILCMD:
        case HP_SDC_STATUS_HILDATA:
                read_lock(&hp_sdc.hook_lock);
                if (hp_sdc.hil != NULL)
                        hp_sdc.hil(irq, dev_id, status, data);
                read_unlock(&hp_sdc.hook_lock);
                break;

        case HP_SDC_STATUS_PUP:
                read_lock(&hp_sdc.hook_lock);
                if (hp_sdc.pup != NULL)
                        hp_sdc.pup(irq, dev_id, status, data);
                else
                        printk(KERN_INFO PREFIX "HP SDC reports successful PUP.\n");
                read_unlock(&hp_sdc.hook_lock);
                break;

        default:
                read_lock(&hp_sdc.hook_lock);
                if (hp_sdc.cooked != NULL)
                        hp_sdc.cooked(irq, dev_id, status, data);
                read_unlock(&hp_sdc.hook_lock);
                break;
        }

        return IRQ_HANDLED;
}


static irqreturn_t hp_sdc_nmisr(int irq, void *dev_id)
{
        int status;

        status = hp_sdc_status_in8();
        printk(KERN_WARNING PREFIX "NMI !\n");

#if 0
        if (status & HP_SDC_NMISTATUS_FHS) {
                read_lock(&hp_sdc.hook_lock);
                if (hp_sdc.timer != NULL)
                        hp_sdc.timer(irq, dev_id, status, 0);
                read_unlock(&hp_sdc.hook_lock);
        } else {
                /* TODO: pass this on to the HIL handler, or do SAK here? */
                printk(KERN_WARNING PREFIX "HIL NMI\n");
        }
#endif

        return IRQ_HANDLED;
}


/***************** Kernel (tasklet) context functions ****************/

unsigned long hp_sdc_put(void);

static void hp_sdc_tasklet(unsigned long foo)
{
        write_lock_irq(&hp_sdc.rtq_lock);

        if (hp_sdc.rcurr >= 0) {
                struct timeval tv;

                do_gettimeofday(&tv);
                if (tv.tv_sec > hp_sdc.rtv.tv_sec)
                        tv.tv_usec += USEC_PER_SEC;

                if (tv.tv_usec - hp_sdc.rtv.tv_usec > HP_SDC_MAX_REG_DELAY) {
                        hp_sdc_transaction *curr;
                        uint8_t tmp;

                        curr = hp_sdc.tq[hp_sdc.rcurr];
                        /* If this turns out to be a normal failure mode
                         * we'll need to figure out a way to communicate
                         * it back to the application. and be less verbose.
                         */
                        printk(KERN_WARNING PREFIX "read timeout (%ius)!\n",
                               (int)(tv.tv_usec - hp_sdc.rtv.tv_usec));
                        curr->idx += hp_sdc.rqty;
                        hp_sdc.rqty = 0;
                        tmp = curr->seq[curr->actidx];
                        curr->seq[curr->actidx] |= HP_SDC_ACT_DEAD;
                        if (tmp & HP_SDC_ACT_SEMAPHORE)
                                if (curr->act.semaphore)
                                        up(curr->act.semaphore);

                        if (tmp & HP_SDC_ACT_CALLBACK) {
                                /* Note this means that irqhooks may be called
                                 * in tasklet/bh context.
                                 */
                                if (curr->act.irqhook)
                                        curr->act.irqhook(0, NULL, 0, 0);
                        }

                        curr->actidx = curr->idx;
                        curr->idx++;
                        hp_sdc.rcurr = -1;
                }
        }
        write_unlock_irq(&hp_sdc.rtq_lock);
        hp_sdc_put();
}

unsigned long hp_sdc_put(void)
{
        hp_sdc_transaction *curr;
        uint8_t act;
        int idx, curridx;

        int limit = 0;

        write_lock(&hp_sdc.lock);

        /* If i8042 buffers are full, we cannot do anything that
           requires output, so we skip to the administrativa. */
        if (hp_sdc.ibf) {
                hp_sdc_status_in8();
                if (hp_sdc.ibf)
                        goto finish;
        }

 anew:
        /* See if we are in the middle of a sequence. */
        if (hp_sdc.wcurr < 0)
                hp_sdc.wcurr = 0;
        read_lock_irq(&hp_sdc.rtq_lock);
        if (hp_sdc.rcurr == hp_sdc.wcurr)
                hp_sdc.wcurr++;
        read_unlock_irq(&hp_sdc.rtq_lock);
        if (hp_sdc.wcurr >= HP_SDC_QUEUE_LEN)
                hp_sdc.wcurr = 0;
        curridx = hp_sdc.wcurr;

        if (hp_sdc.tq[curridx] != NULL)
                goto start;

        while (++curridx != hp_sdc.wcurr) {
                if (curridx >= HP_SDC_QUEUE_LEN) {
                        curridx = -1; /* Wrap to top */
                        continue;
                }
                read_lock_irq(&hp_sdc.rtq_lock);
                if (hp_sdc.rcurr == curridx) {
                        read_unlock_irq(&hp_sdc.rtq_lock);
                        continue;
                }
                read_unlock_irq(&hp_sdc.rtq_lock);
                if (hp_sdc.tq[curridx] != NULL)
                        break; /* Found one. */
        }
        if (curridx == hp_sdc.wcurr) { /* There's nothing queued to do. */
                curridx = -1;
        }
        hp_sdc.wcurr = curridx;

 start:

        /* Check to see if the interrupt mask needs to be set. */
        if (hp_sdc.set_im) {
                hp_sdc_status_out8(hp_sdc.im | HP_SDC_CMD_SET_IM);
                hp_sdc.set_im = 0;
                goto finish;
        }

        if (hp_sdc.wcurr == -1)
                goto done;

        curr = hp_sdc.tq[curridx];
        idx = curr->actidx;

        if (curr->actidx >= curr->endidx) {
                hp_sdc.tq[curridx] = NULL;
                /* Interleave outbound data between the transactions. */
                hp_sdc.wcurr++;
                if (hp_sdc.wcurr >= HP_SDC_QUEUE_LEN)
                        hp_sdc.wcurr = 0;
                goto finish;
        }

        act = curr->seq[idx];
        idx++;

        if (curr->idx >= curr->endidx) {
                if (act & HP_SDC_ACT_DEALLOC)
                        kfree(curr);
                hp_sdc.tq[curridx] = NULL;
                /* Interleave outbound data between the transactions. */
                hp_sdc.wcurr++;
                if (hp_sdc.wcurr >= HP_SDC_QUEUE_LEN)
                        hp_sdc.wcurr = 0;
                goto finish;
        }

        while (act & HP_SDC_ACT_PRECMD) {
                if (curr->idx != idx) {
                        idx++;
                        act &= ~HP_SDC_ACT_PRECMD;
                        break;
                }
                hp_sdc_status_out8(curr->seq[idx]);
                curr->idx++;
                /* act finished? */
                if ((act & HP_SDC_ACT_DURING) == HP_SDC_ACT_PRECMD)
                        goto actdone;
                /* skip quantity field if data-out sequence follows. */
                if (act & HP_SDC_ACT_DATAOUT)
                        curr->idx++;
                goto finish;
        }
        if (act & HP_SDC_ACT_DATAOUT) {
                int qty;

                qty = curr->seq[idx];
                idx++;
                if (curr->idx - idx < qty) {
                        hp_sdc_data_out8(curr->seq[curr->idx]);
                        curr->idx++;
                        /* act finished? */
                        if (curr->idx - idx >= qty &&
                            (act & HP_SDC_ACT_DURING) == HP_SDC_ACT_DATAOUT)
                                goto actdone;
                        goto finish;
                }
                idx += qty;
                act &= ~HP_SDC_ACT_DATAOUT;
        } else
            while (act & HP_SDC_ACT_DATAREG) {
                int mask;
                uint8_t w7[4];

                mask = curr->seq[idx];
                if (idx != curr->idx) {
                        idx++;
                        idx += !!(mask & 1);
                        idx += !!(mask & 2);
                        idx += !!(mask & 4);
                        idx += !!(mask & 8);
                        act &= ~HP_SDC_ACT_DATAREG;
                        break;
                }

                w7[0] = (mask & 1) ? curr->seq[++idx] : hp_sdc.r7[0];
                w7[1] = (mask & 2) ? curr->seq[++idx] : hp_sdc.r7[1];
                w7[2] = (mask & 4) ? curr->seq[++idx] : hp_sdc.r7[2];
                w7[3] = (mask & 8) ? curr->seq[++idx] : hp_sdc.r7[3];

                if (hp_sdc.wi > 0x73 || hp_sdc.wi < 0x70 ||
                    w7[hp_sdc.wi - 0x70] == hp_sdc.r7[hp_sdc.wi - 0x70]) {
                        int i = 0;

                        /* Need to point the write index register */
                        while (i < 4 && w7[i] == hp_sdc.r7[i])
                                i++;

                        if (i < 4) {
                                hp_sdc_status_out8(HP_SDC_CMD_SET_D0 + i);
                                hp_sdc.wi = 0x70 + i;
                                goto finish;
                        }

                        idx++;
                        if ((act & HP_SDC_ACT_DURING) == HP_SDC_ACT_DATAREG)
                                goto actdone;

                        curr->idx = idx;
                        act &= ~HP_SDC_ACT_DATAREG;
                        break;
                }

                hp_sdc_data_out8(w7[hp_sdc.wi - 0x70]);
                hp_sdc.r7[hp_sdc.wi - 0x70] = w7[hp_sdc.wi - 0x70];
                hp_sdc.wi++; /* write index register autoincrements */
                {
                        int i = 0;

                        while ((i < 4) && w7[i] == hp_sdc.r7[i])
                                i++;
                        if (i >= 4) {
                                curr->idx = idx + 1;
                                if ((act & HP_SDC_ACT_DURING) ==
                                    HP_SDC_ACT_DATAREG)
                                        goto actdone;
                        }
                }
                goto finish;
        }
        /* We don't go any further in the command if there is a pending read,
           because we don't want interleaved results. */
        read_lock_irq(&hp_sdc.rtq_lock);
        if (hp_sdc.rcurr >= 0) {
                read_unlock_irq(&hp_sdc.rtq_lock);
                goto finish;
        }
        read_unlock_irq(&hp_sdc.rtq_lock);


        if (act & HP_SDC_ACT_POSTCMD) {
                uint8_t postcmd;

                /* curr->idx should == idx at this point. */
                postcmd = curr->seq[idx];
                curr->idx++;
                if (act & HP_SDC_ACT_DATAIN) {

                        /* Start a new read */
                        hp_sdc.rqty = curr->seq[curr->idx];
                        do_gettimeofday(&hp_sdc.rtv);
                        curr->idx++;
                        /* Still need to lock here in case of spurious irq. */
                        write_lock_irq(&hp_sdc.rtq_lock);
                        hp_sdc.rcurr = curridx;
                        write_unlock_irq(&hp_sdc.rtq_lock);
                        hp_sdc_status_out8(postcmd);
                        goto finish;
                }
                hp_sdc_status_out8(postcmd);
                goto actdone;
        }

 actdone:
        if (act & HP_SDC_ACT_SEMAPHORE)
                up(curr->act.semaphore);
        else if (act & HP_SDC_ACT_CALLBACK)
                curr->act.irqhook(0,NULL,0,0);

        if (curr->idx >= curr->endidx) { /* This transaction is over. */
                if (act & HP_SDC_ACT_DEALLOC)
                        kfree(curr);
                hp_sdc.tq[curridx] = NULL;
        } else {
                curr->actidx = idx + 1;
                curr->idx = idx + 2;
        }
        /* Interleave outbound data between the transactions. */
        hp_sdc.wcurr++;
        if (hp_sdc.wcurr >= HP_SDC_QUEUE_LEN)
                hp_sdc.wcurr = 0;

 finish:
        /* If by some quirk IBF has cleared and our ISR has run to
           see that that has happened, do it all again. */
        if (!hp_sdc.ibf && limit++ < 20)
                goto anew;

 done:
        if (hp_sdc.wcurr >= 0)
                tasklet_schedule(&hp_sdc.task);
        write_unlock(&hp_sdc.lock);

        return 0;
}

/******* Functions called in either user or kernel context ****/
int __hp_sdc_enqueue_transaction(hp_sdc_transaction *this)
{
        int i;

        if (this == NULL) {
                BUG();
                return -EINVAL;
        }

        /* Can't have same transaction on queue twice */
        for (i = 0; i < HP_SDC_QUEUE_LEN; i++)
                if (hp_sdc.tq[i] == this)
                        goto fail;

        this->actidx = 0;
        this->idx = 1;

        /* Search for empty slot */
        for (i = 0; i < HP_SDC_QUEUE_LEN; i++)
                if (hp_sdc.tq[i] == NULL) {
                        hp_sdc.tq[i] = this;
                        tasklet_schedule(&hp_sdc.task);
                        return 0;
                }

        printk(KERN_WARNING PREFIX "No free slot to add transaction.\n");
        return -EBUSY;

 fail:
        printk(KERN_WARNING PREFIX "Transaction add failed: transaction already queued?\n");
        return -EINVAL;
}

int hp_sdc_enqueue_transaction(hp_sdc_transaction *this) {
        unsigned long flags;
        int ret;

        write_lock_irqsave(&hp_sdc.lock, flags);
        ret = __hp_sdc_enqueue_transaction(this);
        write_unlock_irqrestore(&hp_sdc.lock,flags);

        return ret;
}

int hp_sdc_dequeue_transaction(hp_sdc_transaction *this)
{
        unsigned long flags;
        int i;

        write_lock_irqsave(&hp_sdc.lock, flags);

        /* TODO: don't remove it if it's not done. */

        for (i = 0; i < HP_SDC_QUEUE_LEN; i++)
                if (hp_sdc.tq[i] == this)
                        hp_sdc.tq[i] = NULL;

        write_unlock_irqrestore(&hp_sdc.lock, flags);
        return 0;
}



/********************** User context functions **************************/
int hp_sdc_request_timer_irq(hp_sdc_irqhook *callback)
{
        if (callback == NULL || hp_sdc.dev == NULL)
                return -EINVAL;

        write_lock_irq(&hp_sdc.hook_lock);
        if (hp_sdc.timer != NULL) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EBUSY;
        }

        hp_sdc.timer = callback;
        /* Enable interrupts from the timers */
        hp_sdc.im &= ~HP_SDC_IM_FH;
        hp_sdc.im &= ~HP_SDC_IM_PT;
        hp_sdc.im &= ~HP_SDC_IM_TIMERS;
        hp_sdc.set_im = 1;
        write_unlock_irq(&hp_sdc.hook_lock);

        tasklet_schedule(&hp_sdc.task);

        return 0;
}

int hp_sdc_request_hil_irq(hp_sdc_irqhook *callback)
{
        if (callback == NULL || hp_sdc.dev == NULL)
                return -EINVAL;

        write_lock_irq(&hp_sdc.hook_lock);
        if (hp_sdc.hil != NULL) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EBUSY;
        }

        hp_sdc.hil = callback;
        hp_sdc.im &= ~(HP_SDC_IM_HIL | HP_SDC_IM_RESET);
        hp_sdc.set_im = 1;
        write_unlock_irq(&hp_sdc.hook_lock);

        tasklet_schedule(&hp_sdc.task);

        return 0;
}

int hp_sdc_request_cooked_irq(hp_sdc_irqhook *callback)
{
        if (callback == NULL || hp_sdc.dev == NULL)
                return -EINVAL;

        write_lock_irq(&hp_sdc.hook_lock);
        if (hp_sdc.cooked != NULL) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EBUSY;
        }

        /* Enable interrupts from the HIL MLC */
        hp_sdc.cooked = callback;
        hp_sdc.im &= ~(HP_SDC_IM_HIL | HP_SDC_IM_RESET);
        hp_sdc.set_im = 1;
        write_unlock_irq(&hp_sdc.hook_lock);

        tasklet_schedule(&hp_sdc.task);

        return 0;
}

int hp_sdc_release_timer_irq(hp_sdc_irqhook *callback)
{
        write_lock_irq(&hp_sdc.hook_lock);
        if ((callback != hp_sdc.timer) ||
            (hp_sdc.timer == NULL)) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EINVAL;
        }

        /* Disable interrupts from the timers */
        hp_sdc.timer = NULL;
        hp_sdc.im |= HP_SDC_IM_TIMERS;
        hp_sdc.im |= HP_SDC_IM_FH;
        hp_sdc.im |= HP_SDC_IM_PT;
        hp_sdc.set_im = 1;
        write_unlock_irq(&hp_sdc.hook_lock);
        tasklet_schedule(&hp_sdc.task);

        return 0;
}

int hp_sdc_release_hil_irq(hp_sdc_irqhook *callback)
{
        write_lock_irq(&hp_sdc.hook_lock);
        if ((callback != hp_sdc.hil) ||
            (hp_sdc.hil == NULL)) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EINVAL;
        }

        hp_sdc.hil = NULL;
        /* Disable interrupts from HIL only if there is no cooked driver. */
        if(hp_sdc.cooked == NULL) {
                hp_sdc.im |= (HP_SDC_IM_HIL | HP_SDC_IM_RESET);
                hp_sdc.set_im = 1;
        }
        write_unlock_irq(&hp_sdc.hook_lock);
        tasklet_schedule(&hp_sdc.task);

        return 0;
}

int hp_sdc_release_cooked_irq(hp_sdc_irqhook *callback)
{
        write_lock_irq(&hp_sdc.hook_lock);
        if ((callback != hp_sdc.cooked) ||
            (hp_sdc.cooked == NULL)) {
                write_unlock_irq(&hp_sdc.hook_lock);
                return -EINVAL;
        }

        hp_sdc.cooked = NULL;
        /* Disable interrupts from HIL only if there is no raw HIL driver. */
        if(hp_sdc.hil == NULL) {
                hp_sdc.im |= (HP_SDC_IM_HIL | HP_SDC_IM_RESET);
                hp_sdc.set_im = 1;
        }
        write_unlock_irq(&hp_sdc.hook_lock);
        tasklet_schedule(&hp_sdc.task);

        return 0;
}

/************************* Keepalive timer task *********************/

void hp_sdc_kicker (unsigned long data)
{
        tasklet_schedule(&hp_sdc.task);
        /* Re-insert the periodic task. */
        mod_timer(&hp_sdc.kicker, jiffies + HZ);
}

/************************** Module Initialization ***************************/

#if defined(__hppa__)

static const struct parisc_device_id hp_sdc_tbl[] = {
        {
                .hw_type =      HPHW_FIO,
                .hversion_rev = HVERSION_REV_ANY_ID,
                .hversion =     HVERSION_ANY_ID,
                .sversion =     0x73,
         },
        { 0, }
};

MODULE_DEVICE_TABLE(parisc, hp_sdc_tbl);

static int __init hp_sdc_init_hppa(struct parisc_device *d);
static struct delayed_work moduleloader_work;

static struct parisc_driver hp_sdc_driver = {
        .name =         "hp_sdc",
        .id_table =     hp_sdc_tbl,
        .probe =        hp_sdc_init_hppa,
};

#endif /* __hppa__ */

static int __init hp_sdc_init(void)
{
        char *errstr;
        hp_sdc_transaction t_sync;
        uint8_t ts_sync[6];
        struct semaphore s_sync;

        rwlock_init(&hp_sdc.lock);
        rwlock_init(&hp_sdc.ibf_lock);
        rwlock_init(&hp_sdc.rtq_lock);
        rwlock_init(&hp_sdc.hook_lock);

        hp_sdc.timer            = NULL;
        hp_sdc.hil              = NULL;
        hp_sdc.pup              = NULL;
        hp_sdc.cooked           = NULL;
        hp_sdc.im               = HP_SDC_IM_MASK;  /* Mask maskable irqs */
        hp_sdc.set_im           = 1;
        hp_sdc.wi               = 0xff;
        hp_sdc.r7[0]            = 0xff;
        hp_sdc.r7[1]            = 0xff;
        hp_sdc.r7[2]            = 0xff;
        hp_sdc.r7[3]            = 0xff;
        hp_sdc.ibf              = 1;

        memset(&hp_sdc.tq, 0, sizeof(hp_sdc.tq));

        hp_sdc.wcurr            = -1;
        hp_sdc.rcurr            = -1;
        hp_sdc.rqty             = 0;

        hp_sdc.dev_err = -ENODEV;

        errstr = "IO not found for";
        if (!hp_sdc.base_io)
                goto err0;

        errstr = "IRQ not found for";
        if (!hp_sdc.irq)
                goto err0;

        hp_sdc.dev_err = -EBUSY;

#if defined(__hppa__)
        errstr = "IO not available for";
        if (request_region(hp_sdc.data_io, 2, hp_sdc_driver.name))
                goto err0;
#endif

        errstr = "IRQ not available for";
        if (request_irq(hp_sdc.irq, &hp_sdc_isr, IRQF_SHARED|IRQF_SAMPLE_RANDOM,
                        "HP SDC", &hp_sdc))
                goto err1;

        errstr = "NMI not available for";
        if (request_irq(hp_sdc.nmi, &hp_sdc_nmisr, IRQF_SHARED,
                        "HP SDC NMI", &hp_sdc))
                goto err2;

        printk(KERN_INFO PREFIX "HP SDC at 0x%p, IRQ %d (NMI IRQ %d)\n",
               (void *)hp_sdc.base_io, hp_sdc.irq, hp_sdc.nmi);

        hp_sdc_status_in8();
        hp_sdc_data_in8();

        tasklet_init(&hp_sdc.task, hp_sdc_tasklet, 0);

        /* Sync the output buffer registers, thus scheduling hp_sdc_tasklet. */
        t_sync.actidx   = 0;
        t_sync.idx      = 1;
        t_sync.endidx   = 6;
        t_sync.seq      = ts_sync;
        ts_sync[0]      = HP_SDC_ACT_DATAREG | HP_SDC_ACT_SEMAPHORE;
        ts_sync[1]      = 0x0f;
        ts_sync[2] = ts_sync[3] = ts_sync[4] = ts_sync[5] = 0;
        t_sync.act.semaphore = &s_sync;
        init_MUTEX_LOCKED(&s_sync);
        hp_sdc_enqueue_transaction(&t_sync);
        down(&s_sync); /* Wait for t_sync to complete */

        /* Create the keepalive task */
        init_timer(&hp_sdc.kicker);
        hp_sdc.kicker.expires = jiffies + HZ;
        hp_sdc.kicker.function = &hp_sdc_kicker;
        add_timer(&hp_sdc.kicker);

        hp_sdc.dev_err = 0;
        return 0;
 err2:
        free_irq(hp_sdc.irq, &hp_sdc);
 err1:
        release_region(hp_sdc.data_io, 2);
 err0:
        printk(KERN_WARNING PREFIX ": %s SDC IO=0x%p IRQ=0x%x NMI=0x%x\n",
                errstr, (void *)hp_sdc.base_io, hp_sdc.irq, hp_sdc.nmi);
        hp_sdc.dev = NULL;

        return hp_sdc.dev_err;
}

#if defined(__hppa__)

static void request_module_delayed(struct work_struct *work)
{
        request_module("hp_sdc_mlc");
}

static int __init hp_sdc_init_hppa(struct parisc_device *d)
{
        int ret;

        if (!d)
                return 1;
        if (hp_sdc.dev != NULL)
                return 1;       /* We only expect one SDC */

        hp_sdc.dev              = d;
        hp_sdc.irq              = d->irq;
        hp_sdc.nmi              = d->aux_irq;
        hp_sdc.base_io          = d->hpa.start;
        hp_sdc.data_io          = d->hpa.start + 0x800;
        hp_sdc.status_io        = d->hpa.start + 0x801;

        INIT_DELAYED_WORK(&moduleloader_work, request_module_delayed);

        ret = hp_sdc_init();
        /* after sucessfull initialization give SDC some time to settle
         * and then load the hp_sdc_mlc upper layer driver */
        if (!ret)
                schedule_delayed_work(&moduleloader_work,
                        msecs_to_jiffies(2000));

        return ret;
}

#endif /* __hppa__ */

static void hp_sdc_exit(void)
{
        /* do nothing if we don't have a SDC */
        if (!hp_sdc.dev)
                return;

        write_lock_irq(&hp_sdc.lock);

        /* Turn off all maskable "sub-function" irq's. */
        hp_sdc_spin_ibf();
        sdc_writeb(HP_SDC_CMD_SET_IM | HP_SDC_IM_MASK, hp_sdc.status_io);

        /* Wait until we know this has been processed by the i8042 */
        hp_sdc_spin_ibf();

        free_irq(hp_sdc.nmi, &hp_sdc);
        free_irq(hp_sdc.irq, &hp_sdc);
        write_unlock_irq(&hp_sdc.lock);

        del_timer(&hp_sdc.kicker);

        tasklet_kill(&hp_sdc.task);

#if defined(__hppa__)
        cancel_delayed_work_sync(&moduleloader_work);
        if (unregister_parisc_driver(&hp_sdc_driver))
                printk(KERN_WARNING PREFIX "Error unregistering HP SDC");
#endif
}

static int __init hp_sdc_register(void)
{

        hp_sdc_transaction tq_init;
        uint8_t tq_init_seq[5];
        struct semaphore tq_init_sem;
#if defined(__mc68000__)
        mm_segment_t fs;
        unsigned char i;
#endif

        if (hp_sdc_disabled) {
                printk(KERN_WARNING PREFIX "HP SDC driver disabled by no_hpsdc=1.\n");
                return -ENODEV;
        }

        hp_sdc.dev = NULL;
        hp_sdc.dev_err = 0;
#if defined(__hppa__)
        if (register_parisc_driver(&hp_sdc_driver)) {
                printk(KERN_WARNING PREFIX "Error registering SDC with system bus tree.\n");
                return -ENODEV;
        }
#elif defined(__mc68000__)
        if (!MACH_IS_HP300)
            return -ENODEV;

        hp_sdc.irq       = 1;
        hp_sdc.nmi       = 7;
        hp_sdc.base_io   = (unsigned long) 0xf0428000;
        hp_sdc.data_io   = (unsigned long) hp_sdc.base_io + 1;
        hp_sdc.status_io = (unsigned long) hp_sdc.base_io + 3;
        fs = get_fs();
        set_fs(KERNEL_DS);
        if (!get_user(i, (unsigned char *)hp_sdc.data_io))
                hp_sdc.dev = (void *)1;
        set_fs(fs);
        hp_sdc.dev_err   = hp_sdc_init();
#endif
        if (hp_sdc.dev == NULL) {
                printk(KERN_WARNING PREFIX "No SDC found.\n");
                return hp_sdc.dev_err;
        }

        init_MUTEX_LOCKED(&tq_init_sem);

        tq_init.actidx          = 0;
        tq_init.idx             = 1;
        tq_init.endidx          = 5;
        tq_init.seq             = tq_init_seq;
        tq_init.act.semaphore   = &tq_init_sem;

        tq_init_seq[0] =
                HP_SDC_ACT_POSTCMD | HP_SDC_ACT_DATAIN | HP_SDC_ACT_SEMAPHORE;
        tq_init_seq[1] = HP_SDC_CMD_READ_KCC;
        tq_init_seq[2] = 1;
        tq_init_seq[3] = 0;
        tq_init_seq[4] = 0;

        hp_sdc_enqueue_transaction(&tq_init);

        down(&tq_init_sem);
        up(&tq_init_sem);

        if ((tq_init_seq[0] & HP_SDC_ACT_DEAD) == HP_SDC_ACT_DEAD) {
                printk(KERN_WARNING PREFIX "Error reading config byte.\n");
                hp_sdc_exit();
                return -ENODEV;
        }
        hp_sdc.r11 = tq_init_seq[4];
        if (hp_sdc.r11 & HP_SDC_CFG_NEW) {
                const char *str;
                printk(KERN_INFO PREFIX "New style SDC\n");
                tq_init_seq[1] = HP_SDC_CMD_READ_XTD;
                tq_init.actidx          = 0;
                tq_init.idx             = 1;
                down(&tq_init_sem);
                hp_sdc_enqueue_transaction(&tq_init);
                down(&tq_init_sem);
                up(&tq_init_sem);
                if ((tq_init_seq[0] & HP_SDC_ACT_DEAD) == HP_SDC_ACT_DEAD) {
                        printk(KERN_WARNING PREFIX "Error reading extended config byte.\n");
                        return -ENODEV;
                }
                hp_sdc.r7e = tq_init_seq[4];
                HP_SDC_XTD_REV_STRINGS(hp_sdc.r7e & HP_SDC_XTD_REV, str)
                printk(KERN_INFO PREFIX "Revision: %s\n", str);
                if (hp_sdc.r7e & HP_SDC_XTD_BEEPER)
                        printk(KERN_INFO PREFIX "TI SN76494 beeper present\n");
                if (hp_sdc.r7e & HP_SDC_XTD_BBRTC)
                        printk(KERN_INFO PREFIX "OKI MSM-58321 BBRTC present\n");
                printk(KERN_INFO PREFIX "Spunking the self test register to force PUP "
                       "on next firmware reset.\n");
                tq_init_seq[0] = HP_SDC_ACT_PRECMD |
                        HP_SDC_ACT_DATAOUT | HP_SDC_ACT_SEMAPHORE;
                tq_init_seq[1] = HP_SDC_CMD_SET_STR;
                tq_init_seq[2] = 1;
                tq_init_seq[3] = 0;
                tq_init.actidx          = 0;
                tq_init.idx             = 1;
                tq_init.endidx          = 4;
                down(&tq_init_sem);
                hp_sdc_enqueue_transaction(&tq_init);
                down(&tq_init_sem);
                up(&tq_init_sem);
        } else
                printk(KERN_INFO PREFIX "Old style SDC (1820-%s).\n",
                       (hp_sdc.r11 & HP_SDC_CFG_REV) ? "3300" : "2564/3087");

        return 0;
}

module_init(hp_sdc_register);
module_exit(hp_sdc_exit);

/* Timing notes:  These measurements taken on my 64MHz 7100-LC (715/64)
 *                                              cycles cycles-adj    time
 * between two consecutive mfctl(16)'s:              4        n/a    63ns
 * hp_sdc_spin_ibf when idle:                      119        115   1.7us
 * gsc_writeb status register:                      83         79   1.2us
 * IBF to clear after sending SET_IM:             6204       6006    93us
 * IBF to clear after sending LOAD_RT:            4467       4352    68us
 * IBF to clear after sending two LOAD_RTs:      18974      18859   295us
 * READ_T1, read status/data, IRQ, call handler: 35564        n/a   556us
 * cmd to ~IBF READ_T1 2nd time right after:   5158403        n/a    81ms
 * between IRQ received and ~IBF for above:    2578877        n/a    40ms
 *
 * Performance stats after a run of this module configuring HIL and
 * receiving a few mouse events:
 *
 * status in8  282508 cycles 7128 calls
 * status out8   8404 cycles  341 calls
 * data out8     1734 cycles   78 calls
 * isr         174324 cycles  617 calls (includes take)
 * take          1241 cycles    2 calls
 * put        1411504 cycles 6937 calls
 * task       1655209 cycles 6937 calls (includes put)
 *
 */