[NET_SCHED]: Fix endless loops caused by inaccurate qlen counters (part 1)

[hh.org.git] / drivers / scsi / imm.c

/* imm.c   --  low level driver for the IOMEGA MatchMaker
 * parallel port SCSI host adapter.
 * 
 * (The IMM is the embedded controller in the ZIP Plus drive.)
 * 
 * My unoffical company acronym list is 21 pages long:
 *      FLA:    Four letter acronym with built in facility for
 *              future expansion to five letters.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/parport.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <asm/io.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>

/* The following #define is to avoid a clash with hosts.c */
#define IMM_PROBE_SPP   0x0001
#define IMM_PROBE_PS2   0x0002
#define IMM_PROBE_ECR   0x0010
#define IMM_PROBE_EPP17 0x0100
#define IMM_PROBE_EPP19 0x0200


typedef struct {
        struct pardevice *dev;  /* Parport device entry         */
        int base;               /* Actual port address          */
        int base_hi;            /* Hi Base address for ECP-ISA chipset */
        int mode;               /* Transfer mode                */
        struct scsi_cmnd *cur_cmd;      /* Current queued command       */
        struct work_struct imm_tq;      /* Polling interrupt stuff       */
        unsigned long jstart;   /* Jiffies at start             */
        unsigned failed:1;      /* Failure flag                 */
        unsigned dp:1;          /* Data phase present           */
        unsigned rd:1;          /* Read data in data phase      */
        unsigned wanted:1;      /* Parport sharing busy flag    */
        wait_queue_head_t *waiting;
        struct Scsi_Host *host;
        struct list_head list;
} imm_struct;

static void imm_reset_pulse(unsigned int base);
static int device_check(imm_struct *dev);

#include "imm.h"

static inline imm_struct *imm_dev(struct Scsi_Host *host)
{
        return *(imm_struct **)&host->hostdata;
}

static DEFINE_SPINLOCK(arbitration_lock);

static void got_it(imm_struct *dev)
{
        dev->base = dev->dev->port->base;
        if (dev->cur_cmd)
                dev->cur_cmd->SCp.phase = 1;
        else
                wake_up(dev->waiting);
}

static void imm_wakeup(void *ref)
{
        imm_struct *dev = (imm_struct *) ref;
        unsigned long flags;

        spin_lock_irqsave(&arbitration_lock, flags);
        if (dev->wanted) {
                parport_claim(dev->dev);
                got_it(dev);
                dev->wanted = 0;
        }
        spin_unlock_irqrestore(&arbitration_lock, flags);
}

static int imm_pb_claim(imm_struct *dev)
{
        unsigned long flags;
        int res = 1;
        spin_lock_irqsave(&arbitration_lock, flags);
        if (parport_claim(dev->dev) == 0) {
                got_it(dev);
                res = 0;
        }
        dev->wanted = res;
        spin_unlock_irqrestore(&arbitration_lock, flags);
        return res;
}

static void imm_pb_dismiss(imm_struct *dev)
{
        unsigned long flags;
        int wanted;
        spin_lock_irqsave(&arbitration_lock, flags);
        wanted = dev->wanted;
        dev->wanted = 0;
        spin_unlock_irqrestore(&arbitration_lock, flags);
        if (!wanted)
                parport_release(dev->dev);
}

static inline void imm_pb_release(imm_struct *dev)
{
        parport_release(dev->dev);
}

/* This is to give the imm driver a way to modify the timings (and other
 * parameters) by writing to the /proc/scsi/imm/0 file.
 * Very simple method really... (Too simple, no error checking :( )
 * Reason: Kernel hackers HATE having to unload and reload modules for
 * testing...
 * Also gives a method to use a script to obtain optimum timings (TODO)
 */
static inline int imm_proc_write(imm_struct *dev, char *buffer, int length)
{
        unsigned long x;

        if ((length > 5) && (strncmp(buffer, "mode=", 5) == 0)) {
                x = simple_strtoul(buffer + 5, NULL, 0);
                dev->mode = x;
                return length;
        }
        printk("imm /proc: invalid variable\n");
        return (-EINVAL);
}

static int imm_proc_info(struct Scsi_Host *host, char *buffer, char **start,
                        off_t offset, int length, int inout)
{
        imm_struct *dev = imm_dev(host);
        int len = 0;

        if (inout)
                return imm_proc_write(dev, buffer, length);

        len += sprintf(buffer + len, "Version : %s\n", IMM_VERSION);
        len +=
            sprintf(buffer + len, "Parport : %s\n",
                    dev->dev->port->name);
        len +=
            sprintf(buffer + len, "Mode    : %s\n",
                    IMM_MODE_STRING[dev->mode]);

        /* Request for beyond end of buffer */
        if (offset > len)
                return 0;

        *start = buffer + offset;
        len -= offset;
        if (len > length)
                len = length;
        return len;
}

#if IMM_DEBUG > 0
#define imm_fail(x,y) printk("imm: imm_fail(%i) from %s at line %d\n",\
           y, __FUNCTION__, __LINE__); imm_fail_func(x,y);
static inline void
imm_fail_func(imm_struct *dev, int error_code)
#else
static inline void
imm_fail(imm_struct *dev, int error_code)
#endif
{
        /* If we fail a device then we trash status / message bytes */
        if (dev->cur_cmd) {
                dev->cur_cmd->result = error_code << 16;
                dev->failed = 1;
        }
}

/*
 * Wait for the high bit to be set.
 * 
 * In principle, this could be tied to an interrupt, but the adapter
 * doesn't appear to be designed to support interrupts.  We spin on
 * the 0x80 ready bit. 
 */
static unsigned char imm_wait(imm_struct *dev)
{
        int k;
        unsigned short ppb = dev->base;
        unsigned char r;

        w_ctr(ppb, 0x0c);

        k = IMM_SPIN_TMO;
        do {
                r = r_str(ppb);
                k--;
                udelay(1);
        }
        while (!(r & 0x80) && (k));

        /*
         * STR register (LPT base+1) to SCSI mapping:
         *
         * STR      imm     imm
         * ===================================
         * 0x80     S_REQ   S_REQ
         * 0x40     !S_BSY  (????)
         * 0x20     !S_CD   !S_CD
         * 0x10     !S_IO   !S_IO
         * 0x08     (????)  !S_BSY
         *
         * imm      imm     meaning
         * ==================================
         * 0xf0     0xb8    Bit mask
         * 0xc0     0x88    ZIP wants more data
         * 0xd0     0x98    ZIP wants to send more data
         * 0xe0     0xa8    ZIP is expecting SCSI command data
         * 0xf0     0xb8    end of transfer, ZIP is sending status
         */
        w_ctr(ppb, 0x04);
        if (k)
                return (r & 0xb8);

        /* Counter expired - Time out occurred */
        imm_fail(dev, DID_TIME_OUT);
        printk("imm timeout in imm_wait\n");
        return 0;               /* command timed out */
}

static int imm_negotiate(imm_struct * tmp)
{
        /*
         * The following is supposedly the IEEE 1284-1994 negotiate
         * sequence. I have yet to obtain a copy of the above standard
         * so this is a bit of a guess...
         *
         * A fair chunk of this is based on the Linux parport implementation
         * of IEEE 1284.
         *
         * Return 0 if data available
         *        1 if no data available
         */

        unsigned short base = tmp->base;
        unsigned char a, mode;

        switch (tmp->mode) {
        case IMM_NIBBLE:
                mode = 0x00;
                break;
        case IMM_PS2:
                mode = 0x01;
                break;
        default:
                return 0;
        }

        w_ctr(base, 0x04);
        udelay(5);
        w_dtr(base, mode);
        udelay(100);
        w_ctr(base, 0x06);
        udelay(5);
        a = (r_str(base) & 0x20) ? 0 : 1;
        udelay(5);
        w_ctr(base, 0x07);
        udelay(5);
        w_ctr(base, 0x06);

        if (a) {
                printk
                    ("IMM: IEEE1284 negotiate indicates no data available.\n");
                imm_fail(tmp, DID_ERROR);
        }
        return a;
}

/* 
 * Clear EPP timeout bit. 
 */
static inline void epp_reset(unsigned short ppb)
{
        int i;

        i = r_str(ppb);
        w_str(ppb, i);
        w_str(ppb, i & 0xfe);
}

/* 
 * Wait for empty ECP fifo (if we are in ECP fifo mode only)
 */
static inline void ecp_sync(imm_struct *dev)
{
        int i, ppb_hi = dev->base_hi;

        if (ppb_hi == 0)
                return;

        if ((r_ecr(ppb_hi) & 0xe0) == 0x60) {   /* mode 011 == ECP fifo mode */
                for (i = 0; i < 100; i++) {
                        if (r_ecr(ppb_hi) & 0x01)
                                return;
                        udelay(5);
                }
                printk("imm: ECP sync failed as data still present in FIFO.\n");
        }
}

static int imm_byte_out(unsigned short base, const char *buffer, int len)
{
        int i;

        w_ctr(base, 0x4);       /* apparently a sane mode */
        for (i = len >> 1; i; i--) {
                w_dtr(base, *buffer++);
                w_ctr(base, 0x5);       /* Drop STROBE low */
                w_dtr(base, *buffer++);
                w_ctr(base, 0x0);       /* STROBE high + INIT low */
        }
        w_ctr(base, 0x4);       /* apparently a sane mode */
        return 1;               /* All went well - we hope! */
}

static int imm_nibble_in(unsigned short base, char *buffer, int len)
{
        unsigned char l;
        int i;

        /*
         * The following is based on documented timing signals
         */
        w_ctr(base, 0x4);
        for (i = len; i; i--) {
                w_ctr(base, 0x6);
                l = (r_str(base) & 0xf0) >> 4;
                w_ctr(base, 0x5);
                *buffer++ = (r_str(base) & 0xf0) | l;
                w_ctr(base, 0x4);
        }
        return 1;               /* All went well - we hope! */
}

static int imm_byte_in(unsigned short base, char *buffer, int len)
{
        int i;

        /*
         * The following is based on documented timing signals
         */
        w_ctr(base, 0x4);
        for (i = len; i; i--) {
                w_ctr(base, 0x26);
                *buffer++ = r_dtr(base);
                w_ctr(base, 0x25);
        }
        return 1;               /* All went well - we hope! */
}

static int imm_out(imm_struct *dev, char *buffer, int len)
{
        unsigned short ppb = dev->base;
        int r = imm_wait(dev);

        /*
         * Make sure that:
         * a) the SCSI bus is BUSY (device still listening)
         * b) the device is listening
         */
        if ((r & 0x18) != 0x08) {
                imm_fail(dev, DID_ERROR);
                printk("IMM: returned SCSI status %2x\n", r);
                return 0;
        }
        switch (dev->mode) {
        case IMM_EPP_32:
        case IMM_EPP_16:
        case IMM_EPP_8:
                epp_reset(ppb);
                w_ctr(ppb, 0x4);
#ifdef CONFIG_SCSI_IZIP_EPP16
                if (!(((long) buffer | len) & 0x01))
                        outsw(ppb + 4, buffer, len >> 1);
#else
                if (!(((long) buffer | len) & 0x03))
                        outsl(ppb + 4, buffer, len >> 2);
#endif
                else
                        outsb(ppb + 4, buffer, len);
                w_ctr(ppb, 0xc);
                r = !(r_str(ppb) & 0x01);
                w_ctr(ppb, 0xc);
                ecp_sync(dev);
                break;

        case IMM_NIBBLE:
        case IMM_PS2:
                /* 8 bit output, with a loop */
                r = imm_byte_out(ppb, buffer, len);
                break;

        default:
                printk("IMM: bug in imm_out()\n");
                r = 0;
        }
        return r;
}

static int imm_in(imm_struct *dev, char *buffer, int len)
{
        unsigned short ppb = dev->base;
        int r = imm_wait(dev);

        /*
         * Make sure that:
         * a) the SCSI bus is BUSY (device still listening)
         * b) the device is sending data
         */
        if ((r & 0x18) != 0x18) {
                imm_fail(dev, DID_ERROR);
                return 0;
        }
        switch (dev->mode) {
        case IMM_NIBBLE:
                /* 4 bit input, with a loop */
                r = imm_nibble_in(ppb, buffer, len);
                w_ctr(ppb, 0xc);
                break;

        case IMM_PS2:
                /* 8 bit input, with a loop */
                r = imm_byte_in(ppb, buffer, len);
                w_ctr(ppb, 0xc);
                break;

        case IMM_EPP_32:
        case IMM_EPP_16:
        case IMM_EPP_8:
                epp_reset(ppb);
                w_ctr(ppb, 0x24);
#ifdef CONFIG_SCSI_IZIP_EPP16
                if (!(((long) buffer | len) & 0x01))
                        insw(ppb + 4, buffer, len >> 1);
#else
                if (!(((long) buffer | len) & 0x03))
                        insl(ppb + 4, buffer, len >> 2);
#endif
                else
                        insb(ppb + 4, buffer, len);
                w_ctr(ppb, 0x2c);
                r = !(r_str(ppb) & 0x01);
                w_ctr(ppb, 0x2c);
                ecp_sync(dev);
                break;

        default:
                printk("IMM: bug in imm_ins()\n");
                r = 0;
                break;
        }
        return r;
}

static int imm_cpp(unsigned short ppb, unsigned char b)
{
        /*
         * Comments on udelay values refer to the
         * Command Packet Protocol (CPP) timing diagram.
         */

        unsigned char s1, s2, s3;
        w_ctr(ppb, 0x0c);
        udelay(2);              /* 1 usec - infinite */
        w_dtr(ppb, 0xaa);
        udelay(10);             /* 7 usec - infinite */
        w_dtr(ppb, 0x55);
        udelay(10);             /* 7 usec - infinite */
        w_dtr(ppb, 0x00);
        udelay(10);             /* 7 usec - infinite */
        w_dtr(ppb, 0xff);
        udelay(10);             /* 7 usec - infinite */
        s1 = r_str(ppb) & 0xb8;
        w_dtr(ppb, 0x87);
        udelay(10);             /* 7 usec - infinite */
        s2 = r_str(ppb) & 0xb8;
        w_dtr(ppb, 0x78);
        udelay(10);             /* 7 usec - infinite */
        s3 = r_str(ppb) & 0x38;
        /*
         * Values for b are:
         * 0000 00aa    Assign address aa to current device
         * 0010 00aa    Select device aa in EPP Winbond mode
         * 0010 10aa    Select device aa in EPP mode
         * 0011 xxxx    Deselect all devices
         * 0110 00aa    Test device aa
         * 1101 00aa    Select device aa in ECP mode
         * 1110 00aa    Select device aa in Compatible mode
         */
        w_dtr(ppb, b);
        udelay(2);              /* 1 usec - infinite */
        w_ctr(ppb, 0x0c);
        udelay(10);             /* 7 usec - infinite */
        w_ctr(ppb, 0x0d);
        udelay(2);              /* 1 usec - infinite */
        w_ctr(ppb, 0x0c);
        udelay(10);             /* 7 usec - infinite */
        w_dtr(ppb, 0xff);
        udelay(10);             /* 7 usec - infinite */

        /*
         * The following table is electrical pin values.
         * (BSY is inverted at the CTR register)
         *
         *       BSY  ACK  POut SEL  Fault
         * S1    0    X    1    1    1
         * S2    1    X    0    1    1
         * S3    L    X    1    1    S
         *
         * L => Last device in chain
         * S => Selected
         *
         * Observered values for S1,S2,S3 are:
         * Disconnect => f8/58/78
         * Connect    => f8/58/70
         */
        if ((s1 == 0xb8) && (s2 == 0x18) && (s3 == 0x30))
                return 1;       /* Connected */
        if ((s1 == 0xb8) && (s2 == 0x18) && (s3 == 0x38))
                return 0;       /* Disconnected */

        return -1;              /* No device present */
}

static inline int imm_connect(imm_struct *dev, int flag)
{
        unsigned short ppb = dev->base;

        imm_cpp(ppb, 0xe0);     /* Select device 0 in compatible mode */
        imm_cpp(ppb, 0x30);     /* Disconnect all devices */

        if ((dev->mode == IMM_EPP_8) ||
            (dev->mode == IMM_EPP_16) ||
            (dev->mode == IMM_EPP_32))
                return imm_cpp(ppb, 0x28);      /* Select device 0 in EPP mode */
        return imm_cpp(ppb, 0xe0);      /* Select device 0 in compatible mode */
}

static void imm_disconnect(imm_struct *dev)
{
        imm_cpp(dev->base, 0x30);       /* Disconnect all devices */
}

static int imm_select(imm_struct *dev, int target)
{
        int k;
        unsigned short ppb = dev->base;

        /*
         * Firstly we want to make sure there is nothing
         * holding onto the SCSI bus.
         */
        w_ctr(ppb, 0xc);

        k = IMM_SELECT_TMO;
        do {
                k--;
        } while ((r_str(ppb) & 0x08) && (k));

        if (!k)
                return 0;

        /*
         * Now assert the SCSI ID (HOST and TARGET) on the data bus
         */
        w_ctr(ppb, 0x4);
        w_dtr(ppb, 0x80 | (1 << target));
        udelay(1);

        /*
         * Deassert SELIN first followed by STROBE
         */
        w_ctr(ppb, 0xc);
        w_ctr(ppb, 0xd);

        /*
         * ACK should drop low while SELIN is deasserted.
         * FAULT should drop low when the SCSI device latches the bus.
         */
        k = IMM_SELECT_TMO;
        do {
                k--;
        }
        while (!(r_str(ppb) & 0x08) && (k));

        /*
         * Place the interface back into a sane state (status mode)
         */
        w_ctr(ppb, 0xc);
        return (k) ? 1 : 0;
}

static int imm_init(imm_struct *dev)
{
        if (imm_connect(dev, 0) != 1)
                return -EIO;
        imm_reset_pulse(dev->base);
        mdelay(1);      /* Delay to allow devices to settle */
        imm_disconnect(dev);
        mdelay(1);      /* Another delay to allow devices to settle */
        return device_check(dev);
}

static inline int imm_send_command(struct scsi_cmnd *cmd)
{
        imm_struct *dev = imm_dev(cmd->device->host);
        int k;

        /* NOTE: IMM uses byte pairs */
        for (k = 0; k < cmd->cmd_len; k += 2)
                if (!imm_out(dev, &cmd->cmnd[k], 2))
                        return 0;
        return 1;
}

/*
 * The bulk flag enables some optimisations in the data transfer loops,
 * it should be true for any command that transfers data in integral
 * numbers of sectors.
 * 
 * The driver appears to remain stable if we speed up the parallel port
 * i/o in this function, but not elsewhere.
 */
static int imm_completion(struct scsi_cmnd *cmd)
{
        /* Return codes:
         * -1     Error
         *  0     Told to schedule
         *  1     Finished data transfer
         */
        imm_struct *dev = imm_dev(cmd->device->host);
        unsigned short ppb = dev->base;
        unsigned long start_jiffies = jiffies;

        unsigned char r, v;
        int fast, bulk, status;

        v = cmd->cmnd[0];
        bulk = ((v == READ_6) ||
                (v == READ_10) || (v == WRITE_6) || (v == WRITE_10));

        /*
         * We only get here if the drive is ready to comunicate,
         * hence no need for a full imm_wait.
         */
        w_ctr(ppb, 0x0c);
        r = (r_str(ppb) & 0xb8);

        /*
         * while (device is not ready to send status byte)
         *     loop;
         */
        while (r != (unsigned char) 0xb8) {
                /*
                 * If we have been running for more than a full timer tick
                 * then take a rest.
                 */
                if (time_after(jiffies, start_jiffies + 1))
                        return 0;

                /*
                 * FAIL if:
                 * a) Drive status is screwy (!ready && !present)
                 * b) Drive is requesting/sending more data than expected
                 */
                if (((r & 0x88) != 0x88) || (cmd->SCp.this_residual <= 0)) {
                        imm_fail(dev, DID_ERROR);
                        return -1;      /* ERROR_RETURN */
                }
                /* determine if we should use burst I/O */
                if (dev->rd == 0) {
                        fast = (bulk
                                && (cmd->SCp.this_residual >=
                                    IMM_BURST_SIZE)) ? IMM_BURST_SIZE : 2;
                        status = imm_out(dev, cmd->SCp.ptr, fast);
                } else {
                        fast = (bulk
                                && (cmd->SCp.this_residual >=
                                    IMM_BURST_SIZE)) ? IMM_BURST_SIZE : 1;
                        status = imm_in(dev, cmd->SCp.ptr, fast);
                }

                cmd->SCp.ptr += fast;
                cmd->SCp.this_residual -= fast;

                if (!status) {
                        imm_fail(dev, DID_BUS_BUSY);
                        return -1;      /* ERROR_RETURN */
                }
                if (cmd->SCp.buffer && !cmd->SCp.this_residual) {
                        /* if scatter/gather, advance to the next segment */
                        if (cmd->SCp.buffers_residual--) {
                                cmd->SCp.buffer++;
                                cmd->SCp.this_residual =
                                    cmd->SCp.buffer->length;
                                cmd->SCp.ptr =
                                    page_address(cmd->SCp.buffer->page) +
                                    cmd->SCp.buffer->offset;

                                /*
                                 * Make sure that we transfer even number of bytes
                                 * otherwise it makes imm_byte_out() messy.
                                 */
                                if (cmd->SCp.this_residual & 0x01)
                                        cmd->SCp.this_residual++;
                        }
                }
                /* Now check to see if the drive is ready to comunicate */
                w_ctr(ppb, 0x0c);
                r = (r_str(ppb) & 0xb8);

                /* If not, drop back down to the scheduler and wait a timer tick */
                if (!(r & 0x80))
                        return 0;
        }
        return 1;               /* FINISH_RETURN */
}

/*
 * Since the IMM itself doesn't generate interrupts, we use
 * the scheduler's task queue to generate a stream of call-backs and
 * complete the request when the drive is ready.
 */
static void imm_interrupt(void *data)
{
        imm_struct *dev = (imm_struct *) data;
        struct scsi_cmnd *cmd = dev->cur_cmd;
        struct Scsi_Host *host = cmd->device->host;
        unsigned long flags;

        if (!cmd) {
                printk("IMM: bug in imm_interrupt\n");
                return;
        }
        if (imm_engine(dev, cmd)) {
                INIT_WORK(&dev->imm_tq, imm_interrupt, (void *) dev);
                schedule_delayed_work(&dev->imm_tq, 1);
                return;
        }
        /* Command must of completed hence it is safe to let go... */
#if IMM_DEBUG > 0
        switch ((cmd->result >> 16) & 0xff) {
        case DID_OK:
                break;
        case DID_NO_CONNECT:
                printk("imm: no device at SCSI ID %i\n", cmd->device->id);
                break;
        case DID_BUS_BUSY:
                printk("imm: BUS BUSY - EPP timeout detected\n");
                break;
        case DID_TIME_OUT:
                printk("imm: unknown timeout\n");
                break;
        case DID_ABORT:
                printk("imm: told to abort\n");
                break;
        case DID_PARITY:
                printk("imm: parity error (???)\n");
                break;
        case DID_ERROR:
                printk("imm: internal driver error\n");
                break;
        case DID_RESET:
                printk("imm: told to reset device\n");
                break;
        case DID_BAD_INTR:
                printk("imm: bad interrupt (???)\n");
                break;
        default:
                printk("imm: bad return code (%02x)\n",
                       (cmd->result >> 16) & 0xff);
        }
#endif

        if (cmd->SCp.phase > 1)
                imm_disconnect(dev);

        imm_pb_dismiss(dev);

        spin_lock_irqsave(host->host_lock, flags);
        dev->cur_cmd = NULL;
        cmd->scsi_done(cmd);
        spin_unlock_irqrestore(host->host_lock, flags);
        return;
}

static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
{
        unsigned short ppb = dev->base;
        unsigned char l = 0, h = 0;
        int retv, x;

        /* First check for any errors that may have occurred
         * Here we check for internal errors
         */
        if (dev->failed)
                return 0;

        switch (cmd->SCp.phase) {
        case 0:         /* Phase 0 - Waiting for parport */
                if (time_after(jiffies, dev->jstart + HZ)) {
                        /*
                         * We waited more than a second
                         * for parport to call us
                         */
                        imm_fail(dev, DID_BUS_BUSY);
                        return 0;
                }
                return 1;       /* wait until imm_wakeup claims parport */
                /* Phase 1 - Connected */
        case 1:
                imm_connect(dev, CONNECT_EPP_MAYBE);
                cmd->SCp.phase++;

                /* Phase 2 - We are now talking to the scsi bus */
        case 2:
                if (!imm_select(dev, scmd_id(cmd))) {
                        imm_fail(dev, DID_NO_CONNECT);
                        return 0;
                }
                cmd->SCp.phase++;

                /* Phase 3 - Ready to accept a command */
        case 3:
                w_ctr(ppb, 0x0c);
                if (!(r_str(ppb) & 0x80))
                        return 1;

                if (!imm_send_command(cmd))
                        return 0;
                cmd->SCp.phase++;

                /* Phase 4 - Setup scatter/gather buffers */
        case 4:
                if (cmd->use_sg) {
                        /* if many buffers are available, start filling the first */
                        cmd->SCp.buffer =
                            (struct scatterlist *) cmd->request_buffer;
                        cmd->SCp.this_residual = cmd->SCp.buffer->length;
                        cmd->SCp.ptr =
                            page_address(cmd->SCp.buffer->page) +
                            cmd->SCp.buffer->offset;
                } else {
                        /* else fill the only available buffer */
                        cmd->SCp.buffer = NULL;
                        cmd->SCp.this_residual = cmd->request_bufflen;
                        cmd->SCp.ptr = cmd->request_buffer;
                }
                cmd->SCp.buffers_residual = cmd->use_sg - 1;
                cmd->SCp.phase++;
                if (cmd->SCp.this_residual & 0x01)
                        cmd->SCp.this_residual++;
                /* Phase 5 - Pre-Data transfer stage */
        case 5:
                /* Spin lock for BUSY */
                w_ctr(ppb, 0x0c);
                if (!(r_str(ppb) & 0x80))
                        return 1;

                /* Require negotiation for read requests */
                x = (r_str(ppb) & 0xb8);
                dev->rd = (x & 0x10) ? 1 : 0;
                dev->dp = (x & 0x20) ? 0 : 1;

                if ((dev->dp) && (dev->rd))
                        if (imm_negotiate(dev))
                                return 0;
                cmd->SCp.phase++;

                /* Phase 6 - Data transfer stage */
        case 6:
                /* Spin lock for BUSY */
                w_ctr(ppb, 0x0c);
                if (!(r_str(ppb) & 0x80))
                        return 1;

                if (dev->dp) {
                        retv = imm_completion(cmd);
                        if (retv == -1)
                                return 0;
                        if (retv == 0)
                                return 1;
                }
                cmd->SCp.phase++;

                /* Phase 7 - Post data transfer stage */
        case 7:
                if ((dev->dp) && (dev->rd)) {
                        if ((dev->mode == IMM_NIBBLE) || (dev->mode == IMM_PS2)) {
                                w_ctr(ppb, 0x4);
                                w_ctr(ppb, 0xc);
                                w_ctr(ppb, 0xe);
                                w_ctr(ppb, 0x4);
                        }
                }
                cmd->SCp.phase++;

                /* Phase 8 - Read status/message */
        case 8:
                /* Check for data overrun */
                if (imm_wait(dev) != (unsigned char) 0xb8) {
                        imm_fail(dev, DID_ERROR);
                        return 0;
                }
                if (imm_negotiate(dev))
                        return 0;
                if (imm_in(dev, &l, 1)) {       /* read status byte */
                        /* Check for optional message byte */
                        if (imm_wait(dev) == (unsigned char) 0xb8)
                                imm_in(dev, &h, 1);
                        cmd->result = (DID_OK << 16) + (l & STATUS_MASK);
                }
                if ((dev->mode == IMM_NIBBLE) || (dev->mode == IMM_PS2)) {
                        w_ctr(ppb, 0x4);
                        w_ctr(ppb, 0xc);
                        w_ctr(ppb, 0xe);
                        w_ctr(ppb, 0x4);
                }
                return 0;       /* Finished */
                break;

        default:
                printk("imm: Invalid scsi phase\n");
        }
        return 0;
}

static int imm_queuecommand(struct scsi_cmnd *cmd,
                void (*done)(struct scsi_cmnd *))
{
        imm_struct *dev = imm_dev(cmd->device->host);

        if (dev->cur_cmd) {
                printk("IMM: bug in imm_queuecommand\n");
                return 0;
        }
        dev->failed = 0;
        dev->jstart = jiffies;
        dev->cur_cmd = cmd;
        cmd->scsi_done = done;
        cmd->result = DID_ERROR << 16;  /* default return code */
        cmd->SCp.phase = 0;     /* bus free */

        INIT_WORK(&dev->imm_tq, imm_interrupt, dev);
        schedule_work(&dev->imm_tq);

        imm_pb_claim(dev);

        return 0;
}

/*
 * Apparently the disk->capacity attribute is off by 1 sector 
 * for all disk drives.  We add the one here, but it should really
 * be done in sd.c.  Even if it gets fixed there, this will still
 * work.
 */
static int imm_biosparam(struct scsi_device *sdev, struct block_device *dev,
                         sector_t capacity, int ip[])
{
        ip[0] = 0x40;
        ip[1] = 0x20;
        ip[2] = ((unsigned long) capacity + 1) / (ip[0] * ip[1]);
        if (ip[2] > 1024) {
                ip[0] = 0xff;
                ip[1] = 0x3f;
                ip[2] = ((unsigned long) capacity + 1) / (ip[0] * ip[1]);
        }
        return 0;
}

static int imm_abort(struct scsi_cmnd *cmd)
{
        imm_struct *dev = imm_dev(cmd->device->host);
        /*
         * There is no method for aborting commands since Iomega
         * have tied the SCSI_MESSAGE line high in the interface
         */

        switch (cmd->SCp.phase) {
        case 0:         /* Do not have access to parport */
        case 1:         /* Have not connected to interface */
                dev->cur_cmd = NULL;    /* Forget the problem */
                return SUCCESS;
                break;
        default:                /* SCSI command sent, can not abort */
                return FAILED;
                break;
        }
}

static void imm_reset_pulse(unsigned int base)
{
        w_ctr(base, 0x04);
        w_dtr(base, 0x40);
        udelay(1);
        w_ctr(base, 0x0c);
        w_ctr(base, 0x0d);
        udelay(50);
        w_ctr(base, 0x0c);
        w_ctr(base, 0x04);
}

static int imm_reset(struct scsi_cmnd *cmd)
{
        imm_struct *dev = imm_dev(cmd->device->host);

        if (cmd->SCp.phase)
                imm_disconnect(dev);
        dev->cur_cmd = NULL;    /* Forget the problem */

        imm_connect(dev, CONNECT_NORMAL);
        imm_reset_pulse(dev->base);
        mdelay(1);              /* device settle delay */
        imm_disconnect(dev);
        mdelay(1);              /* device settle delay */
        return SUCCESS;
}

static int device_check(imm_struct *dev)
{
        /* This routine looks for a device and then attempts to use EPP
           to send a command. If all goes as planned then EPP is available. */

        static char cmd[6] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
        int loop, old_mode, status, k, ppb = dev->base;
        unsigned char l;

        old_mode = dev->mode;
        for (loop = 0; loop < 8; loop++) {
                /* Attempt to use EPP for Test Unit Ready */
                if ((ppb & 0x0007) == 0x0000)
                        dev->mode = IMM_EPP_32;

              second_pass:
                imm_connect(dev, CONNECT_EPP_MAYBE);
                /* Select SCSI device */
                if (!imm_select(dev, loop)) {
                        imm_disconnect(dev);
                        continue;
                }
                printk("imm: Found device at ID %i, Attempting to use %s\n",
                       loop, IMM_MODE_STRING[dev->mode]);

                /* Send SCSI command */
                status = 1;
                w_ctr(ppb, 0x0c);
                for (l = 0; (l < 3) && (status); l++)
                        status = imm_out(dev, &cmd[l << 1], 2);

                if (!status) {
                        imm_disconnect(dev);
                        imm_connect(dev, CONNECT_EPP_MAYBE);
                        imm_reset_pulse(dev->base);
                        udelay(1000);
                        imm_disconnect(dev);
                        udelay(1000);
                        if (dev->mode == IMM_EPP_32) {
                                dev->mode = old_mode;
                                goto second_pass;
                        }
                        printk("imm: Unable to establish communication\n");
                        return -EIO;
                }
                w_ctr(ppb, 0x0c);

                k = 1000000;    /* 1 Second */
                do {
                        l = r_str(ppb);
                        k--;
                        udelay(1);
                } while (!(l & 0x80) && (k));

                l &= 0xb8;

                if (l != 0xb8) {
                        imm_disconnect(dev);
                        imm_connect(dev, CONNECT_EPP_MAYBE);
                        imm_reset_pulse(dev->base);
                        udelay(1000);
                        imm_disconnect(dev);
                        udelay(1000);
                        if (dev->mode == IMM_EPP_32) {
                                dev->mode = old_mode;
                                goto second_pass;
                        }
                        printk
                            ("imm: Unable to establish communication\n");
                        return -EIO;
                }
                imm_disconnect(dev);
                printk
                    ("imm: Communication established at 0x%x with ID %i using %s\n",
                     ppb, loop, IMM_MODE_STRING[dev->mode]);
                imm_connect(dev, CONNECT_EPP_MAYBE);
                imm_reset_pulse(dev->base);
                udelay(1000);
                imm_disconnect(dev);
                udelay(1000);
                return 0;
        }
        printk("imm: No devices found\n");
        return -ENODEV;
}

/*
 * imm cannot deal with highmem, so this causes all IO pages for this host
 * to reside in low memory (hence mapped)
 */
static int imm_adjust_queue(struct scsi_device *device)
{
        blk_queue_bounce_limit(device->request_queue, BLK_BOUNCE_HIGH);
        return 0;
}

static struct scsi_host_template imm_template = {
        .module                 = THIS_MODULE,
        .proc_name              = "imm",
        .proc_info              = imm_proc_info,
        .name                   = "Iomega VPI2 (imm) interface",
        .queuecommand           = imm_queuecommand,
        .eh_abort_handler       = imm_abort,
        .eh_bus_reset_handler   = imm_reset,
        .eh_host_reset_handler  = imm_reset,
        .bios_param             = imm_biosparam,
        .this_id                = 7,
        .sg_tablesize           = SG_ALL,
        .cmd_per_lun            = 1,
        .use_clustering         = ENABLE_CLUSTERING,
        .can_queue              = 1,
        .slave_alloc            = imm_adjust_queue,
};

/***************************************************************************
 *                   Parallel port probing routines                        *
 ***************************************************************************/

static LIST_HEAD(imm_hosts);

static int __imm_attach(struct parport *pb)
{
        struct Scsi_Host *host;
        imm_struct *dev;
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(waiting);
        DEFINE_WAIT(wait);
        int ports;
        int modes, ppb;
        int err = -ENOMEM;

        init_waitqueue_head(&waiting);

        dev = kmalloc(sizeof(imm_struct), GFP_KERNEL);
        if (!dev)
                return -ENOMEM;

        memset(dev, 0, sizeof(imm_struct));

        dev->base = -1;
        dev->mode = IMM_AUTODETECT;
        INIT_LIST_HEAD(&dev->list);

        dev->dev = parport_register_device(pb, "imm", NULL, imm_wakeup,
                                                NULL, 0, dev);

        if (!dev->dev)
                goto out;


        /* Claim the bus so it remembers what we do to the control
         * registers. [ CTR and ECP ]
         */
        err = -EBUSY;
        dev->waiting = &waiting;
        prepare_to_wait(&waiting, &wait, TASK_UNINTERRUPTIBLE);
        if (imm_pb_claim(dev))
                schedule_timeout(3 * HZ);
        if (dev->wanted) {
                printk(KERN_ERR "imm%d: failed to claim parport because "
                        "a pardevice is owning the port for too long "
                        "time!\n", pb->number);
                imm_pb_dismiss(dev);
                dev->waiting = NULL;
                finish_wait(&waiting, &wait);
                goto out1;
        }
        dev->waiting = NULL;
        finish_wait(&waiting, &wait);
        ppb = dev->base = dev->dev->port->base;
        dev->base_hi = dev->dev->port->base_hi;
        w_ctr(ppb, 0x0c);
        modes = dev->dev->port->modes;

        /* Mode detection works up the chain of speed
         * This avoids a nasty if-then-else-if-... tree
         */
        dev->mode = IMM_NIBBLE;

        if (modes & PARPORT_MODE_TRISTATE)
                dev->mode = IMM_PS2;

        /* Done configuration */

        err = imm_init(dev);

        imm_pb_release(dev);

        if (err)
                goto out1;

        /* now the glue ... */
        if (dev->mode == IMM_NIBBLE || dev->mode == IMM_PS2)
                ports = 3;
        else
                ports = 8;

        INIT_WORK(&dev->imm_tq, imm_interrupt, dev);

        err = -ENOMEM;
        host = scsi_host_alloc(&imm_template, sizeof(imm_struct *));
        if (!host)
                goto out1;
        host->io_port = pb->base;
        host->n_io_port = ports;
        host->dma_channel = -1;
        host->unique_id = pb->number;
        *(imm_struct **)&host->hostdata = dev;
        dev->host = host;
        list_add_tail(&dev->list, &imm_hosts);
        err = scsi_add_host(host, NULL);
        if (err)
                goto out2;
        scsi_scan_host(host);
        return 0;

out2:
        list_del_init(&dev->list);
        scsi_host_put(host);
out1:
        parport_unregister_device(dev->dev);
out:
        kfree(dev);
        return err;
}

static void imm_attach(struct parport *pb)
{
        __imm_attach(pb);
}

static void imm_detach(struct parport *pb)
{
        imm_struct *dev;
        list_for_each_entry(dev, &imm_hosts, list) {
                if (dev->dev->port == pb) {
                        list_del_init(&dev->list);
                        scsi_remove_host(dev->host);
                        scsi_host_put(dev->host);
                        parport_unregister_device(dev->dev);
                        kfree(dev);
                        break;
                }
        }
}

static struct parport_driver imm_driver = {
        .name   = "imm",
        .attach = imm_attach,
        .detach = imm_detach,
};

static int __init imm_driver_init(void)
{
        printk("imm: Version %s\n", IMM_VERSION);
        return parport_register_driver(&imm_driver);
}

static void __exit imm_driver_exit(void)
{
        parport_unregister_driver(&imm_driver);
}

module_init(imm_driver_init);
module_exit(imm_driver_exit);

MODULE_LICENSE("GPL");