/* ppa.c   --  low level driver for the IOMEGA PPA3 
 * parallel port SCSI host adapter.
 * 
 * (The PPA3 is the embedded controller in the ZIP drive.)
 * 
 * (c) 1995,1996 Grant R. Guenther, grant@torque.net,
 * under the terms of the GNU General Public License.
 * 
 */

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

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


static void ppa_reset_pulse(unsigned int base);

typedef struct {
        struct pardevice *dev;  /* Parport device entry         */
        int base;               /* Actual port address          */
        int mode;               /* Transfer mode                */
        struct scsi_cmnd *cur_cmd;      /* Current queued command       */
        struct delayed_work ppa_tq;     /* Polling interrupt stuff       */
        unsigned long jstart;   /* Jiffies at start             */
        unsigned long recon_tmo;        /* How many usecs to wait for reconnection (6th bit) */
        unsigned int failed:1;  /* Failure flag                 */
        unsigned wanted:1;      /* Parport sharing busy flag    */
        unsigned int dev_no;    /* Device number                */
        wait_queue_head_t *waiting;
        struct Scsi_Host *host;
        struct list_head list;
} ppa_struct;

#include  "ppa.h"

static unsigned int mode = PPA_AUTODETECT;
module_param(mode, uint, 0644);
MODULE_PARM_DESC(mode, "Transfer mode (0 = Autodetect, 1 = SPP 4-bit, "
        "2 = SPP 8-bit, 3 = EPP 8-bit, 4 = EPP 16-bit, 5 = EPP 32-bit");

static struct scsi_pointer *ppa_scsi_pointer(struct scsi_cmnd *cmd)
{
        return scsi_cmd_priv(cmd);
}

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

static DEFINE_SPINLOCK(arbitration_lock);

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

static void ppa_wakeup(void *ref)
{
        ppa_struct *dev = (ppa_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);
        return;
}

static int ppa_pb_claim(ppa_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 ppa_pb_dismiss(ppa_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 ppa_pb_release(ppa_struct *dev)
{
        parport_release(dev->dev);
}

/*
 * Start of Chipset kludges
 */

/* This is to give the ppa driver a way to modify the timings (and other
 * parameters) by writing to the /proc/scsi/ppa/0 file.
 * Very simple method really... (To 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 ppa_write_info(struct Scsi_Host *host, char *buffer, int length)
{
        ppa_struct *dev = ppa_dev(host);
        unsigned long x;

        if ((length > 5) && (strncmp(buffer, "mode=", 5) == 0)) {
                x = simple_strtoul(buffer + 5, NULL, 0);
                dev->mode = x;
                return length;
        }
        if ((length > 10) && (strncmp(buffer, "recon_tmo=", 10) == 0)) {
                x = simple_strtoul(buffer + 10, NULL, 0);
                dev->recon_tmo = x;
                printk(KERN_INFO "ppa: recon_tmo set to %ld\n", x);
                return length;
        }
        printk(KERN_WARNING "ppa /proc: invalid variable\n");
        return -EINVAL;
}

static int ppa_show_info(struct seq_file *m, struct Scsi_Host *host)
{
        ppa_struct *dev = ppa_dev(host);

        seq_printf(m, "Version : %s\n", PPA_VERSION);
        seq_printf(m, "Parport : %s\n", dev->dev->port->name);
        seq_printf(m, "Mode    : %s\n", PPA_MODE_STRING[dev->mode]);
#if PPA_DEBUG > 0
        seq_printf(m, "recon_tmo : %lu\n", dev->recon_tmo);
#endif
        return 0;
}

static int device_check(ppa_struct *dev, bool autodetect);

#if PPA_DEBUG > 0
#define ppa_fail(x,y) printk("ppa: ppa_fail(%i) from %s at line %d\n",\
           y, __func__, __LINE__); ppa_fail_func(x,y);
static inline void ppa_fail_func(ppa_struct *dev, int error_code)
#else
static inline void ppa_fail(ppa_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 ppa_wait(ppa_struct *dev)
{
        int k;
        unsigned short ppb = dev->base;
        unsigned char r;

        k = PPA_SPIN_TMO;
        /* Wait for bit 6 and 7 - PJC */
        for (r = r_str(ppb); ((r & 0xc0) != 0xc0) && (k); k--) {
                udelay(1);
                r = r_str(ppb);
        }

        /*
         * return some status information.
         * Semantics: 0xc0 = ZIP wants more data
         *            0xd0 = ZIP wants to send more data
         *            0xe0 = ZIP is expecting SCSI command data
         *            0xf0 = end of transfer, ZIP is sending status
         */
        if (k)
                return (r & 0xf0);

        /* Counter expired - Time out occurred */
        ppa_fail(dev, DID_TIME_OUT);
        printk(KERN_WARNING "ppa timeout in ppa_wait\n");
        return 0;               /* command timed out */
}

/*
 * 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(ppa_struct *dev)
{
        int i, ppb_hi = dev->dev->port->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(KERN_WARNING "ppa: ECP sync failed as data still present in FIFO.\n");
        }
}

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

        for (i = len; i; i--) {
                w_dtr(base, *buffer++);
                w_ctr(base, 0xe);
                w_ctr(base, 0xc);
        }
        return 1;               /* All went well - we hope! */
}

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

        for (i = len; i; i--) {
                *buffer++ = r_dtr(base);
                w_ctr(base, 0x27);
                w_ctr(base, 0x25);
        }
        return 1;               /* All went well - we hope! */
}

static int ppa_nibble_in(unsigned short base, char *buffer, int len)
{
        for (; len; len--) {
                unsigned char h;

                w_ctr(base, 0x4);
                h = r_str(base) & 0xf0;
                w_ctr(base, 0x6);
                *buffer++ = h | ((r_str(base) & 0xf0) >> 4);
        }
        return 1;               /* All went well - we hope! */
}

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

        r = ppa_wait(dev);

        if ((r & 0x50) != 0x40) {
                ppa_fail(dev, DID_ERROR);
                return 0;
        }
        switch (dev->mode) {
        case PPA_NIBBLE:
        case PPA_PS2:
                /* 8 bit output, with a loop */
                r = ppa_byte_out(ppb, buffer, len);
                break;

        case PPA_EPP_32:
        case PPA_EPP_16:
        case PPA_EPP_8:
                epp_reset(ppb);
                w_ctr(ppb, 0x4);
                if (dev->mode == PPA_EPP_32 && !(((long) buffer | len) & 0x03))
                        outsl(ppb + 4, buffer, len >> 2);
                else if (dev->mode == PPA_EPP_16 && !(((long) buffer | len) & 0x01))
                        outsw(ppb + 4, buffer, len >> 1);
                else
                        outsb(ppb + 4, buffer, len);
                w_ctr(ppb, 0xc);
                r = !(r_str(ppb) & 0x01);
                w_ctr(ppb, 0xc);
                ecp_sync(dev);
                break;

        default:
                printk(KERN_ERR "PPA: bug in ppa_out()\n");
                r = 0;
        }
        return r;
}

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

        r = ppa_wait(dev);

        if ((r & 0x50) != 0x50) {
                ppa_fail(dev, DID_ERROR);
                return 0;
        }
        switch (dev->mode) {
        case PPA_NIBBLE:
                /* 4 bit input, with a loop */
                r = ppa_nibble_in(ppb, buffer, len);
                w_ctr(ppb, 0xc);
                break;

        case PPA_PS2:
                /* 8 bit input, with a loop */
                w_ctr(ppb, 0x25);
                r = ppa_byte_in(ppb, buffer, len);
                w_ctr(ppb, 0x4);
                w_ctr(ppb, 0xc);
                break;

        case PPA_EPP_32:
        case PPA_EPP_16:
        case PPA_EPP_8:
                epp_reset(ppb);
                w_ctr(ppb, 0x24);
                if (dev->mode == PPA_EPP_32 && !(((long) buffer | len) & 0x03))
                        insl(ppb + 4, buffer, len >> 2);
                else if (dev->mode == PPA_EPP_16 && !(((long) buffer | len) & 0x01))
                        insw(ppb + 4, buffer, len >> 1);
                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(KERN_ERR "PPA: bug in ppa_ins()\n");
                r = 0;
                break;
        }
        return r;
}

/* end of ppa_io.h */
static inline void ppa_d_pulse(unsigned short ppb, unsigned char b)
{
        w_dtr(ppb, b);
        w_ctr(ppb, 0xc);
        w_ctr(ppb, 0xe);
        w_ctr(ppb, 0xc);
        w_ctr(ppb, 0x4);
        w_ctr(ppb, 0xc);
}

static void ppa_disconnect(ppa_struct *dev)
{
        unsigned short ppb = dev->base;

        ppa_d_pulse(ppb, 0);
        ppa_d_pulse(ppb, 0x3c);
        ppa_d_pulse(ppb, 0x20);
        ppa_d_pulse(ppb, 0xf);
}

static inline void ppa_c_pulse(unsigned short ppb, unsigned char b)
{
        w_dtr(ppb, b);
        w_ctr(ppb, 0x4);
        w_ctr(ppb, 0x6);
        w_ctr(ppb, 0x4);
        w_ctr(ppb, 0xc);
}

static inline void ppa_connect(ppa_struct *dev, int flag)
{
        unsigned short ppb = dev->base;

        ppa_c_pulse(ppb, 0);
        ppa_c_pulse(ppb, 0x3c);
        ppa_c_pulse(ppb, 0x20);
        if ((flag == CONNECT_EPP_MAYBE) && IN_EPP_MODE(dev->mode))
                ppa_c_pulse(ppb, 0xcf);
        else
                ppa_c_pulse(ppb, 0x8f);
}

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

        /*
         * Bit 6 (0x40) is the device selected bit.
         * First we must wait till the current device goes off line...
         */
        k = PPA_SELECT_TMO;
        do {
                k--;
                udelay(1);
        } while ((r_str(ppb) & 0x40) && (k));
        if (!k)
                return 0;

        w_dtr(ppb, (1 << target));
        w_ctr(ppb, 0xe);
        w_ctr(ppb, 0xc);
        w_dtr(ppb, 0x80);       /* This is NOT the initator */
        w_ctr(ppb, 0x8);

        k = PPA_SELECT_TMO;
        do {
                k--;
                udelay(1);
        }
        while (!(r_str(ppb) & 0x40) && (k));
        if (!k)
                return 0;

        return 1;
}

/* 
 * This is based on a trace of what the Iomega DOS 'guest' driver does.
 * I've tried several different kinds of parallel ports with guest and
 * coded this to react in the same ways that it does.
 * 
 * The return value from this function is just a hint about where the
 * handshaking failed.
 * 
 */
static int ppa_init(ppa_struct *dev)
{
        int retv;
        unsigned short ppb = dev->base;
        bool autodetect = dev->mode == PPA_AUTODETECT;

        if (autodetect) {
                int modes = dev->dev->port->modes;
                int ppb_hi = dev->dev->port->base_hi;

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

                if (modes & PARPORT_MODE_TRISTATE)
                        dev->mode = PPA_PS2;

                if (modes & PARPORT_MODE_ECP) {
                        w_ecr(ppb_hi, 0x20);
                        dev->mode = PPA_PS2;
                }
                if ((modes & PARPORT_MODE_EPP) && (modes & PARPORT_MODE_ECP))
                        w_ecr(ppb_hi, 0x80);
        }

        ppa_disconnect(dev);
        ppa_connect(dev, CONNECT_NORMAL);

        retv = 2;               /* Failed */

        w_ctr(ppb, 0xe);
        if ((r_str(ppb) & 0x08) == 0x08)
                retv--;

        w_ctr(ppb, 0xc);
        if ((r_str(ppb) & 0x08) == 0x00)
                retv--;

        if (!retv)
                ppa_reset_pulse(ppb);
        udelay(1000);           /* Allow devices to settle down */
        ppa_disconnect(dev);
        udelay(1000);           /* Another delay to allow devices to settle */

        if (retv)
                return -EIO;

        return device_check(dev, autodetect);
}

static inline int ppa_send_command(struct scsi_cmnd *cmd)
{
        ppa_struct *dev = ppa_dev(cmd->device->host);
        int k;

        w_ctr(dev->base, 0x0c);

        for (k = 0; k < cmd->cmd_len; k++)
                if (!ppa_out(dev, &cmd->cmnd[k], 1))
                        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 ppa_completion(struct scsi_cmnd *const cmd)
{
        /* Return codes:
         * -1     Error
         *  0     Told to schedule
         *  1     Finished data transfer
         */
        struct scsi_pointer *scsi_pointer = ppa_scsi_pointer(cmd);
        ppa_struct *dev = ppa_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 ppa_wait.
         */
        r = (r_str(ppb) & 0xf0);

        while (r != (unsigned char) 0xf0) {
                /*
                 * 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;

                if (scsi_pointer->this_residual <= 0) {
                        ppa_fail(dev, DID_ERROR);
                        return -1;      /* ERROR_RETURN */
                }

                /* On some hardware we have SCSI disconnected (6th bit low)
                 * for about 100usecs. It is too expensive to wait a 
                 * tick on every loop so we busy wait for no more than
                 * 500usecs to give the drive a chance first. We do not 
                 * change things for "normal" hardware since generally 
                 * the 6th bit is always high.
                 * This makes the CPU load higher on some hardware 
                 * but otherwise we can not get more than 50K/secs 
                 * on this problem hardware.
                 */
                if ((r & 0xc0) != 0xc0) {
                        /* Wait for reconnection should be no more than 
                         * jiffy/2 = 5ms = 5000 loops
                         */
                        unsigned long k = dev->recon_tmo;
                        for (; k && ((r = (r_str(ppb) & 0xf0)) & 0xc0) != 0xc0;
                             k--)
                                udelay(1);

                        if (!k)
                                return 0;
                }

                /* determine if we should use burst I/O */
                fast = bulk && scsi_pointer->this_residual >= PPA_BURST_SIZE ?
                        PPA_BURST_SIZE : 1;

                if (r == (unsigned char) 0xc0)
                        status = ppa_out(dev, scsi_pointer->ptr, fast);
                else
                        status = ppa_in(dev, scsi_pointer->ptr, fast);

                scsi_pointer->ptr += fast;
                scsi_pointer->this_residual -= fast;

                if (!status) {
                        ppa_fail(dev, DID_BUS_BUSY);
                        return -1;      /* ERROR_RETURN */
                }
                if (scsi_pointer->buffer && !scsi_pointer->this_residual) {
                        /* if scatter/gather, advance to the next segment */
                        if (scsi_pointer->buffers_residual--) {
                                scsi_pointer->buffer =
                                        sg_next(scsi_pointer->buffer);
                                scsi_pointer->this_residual =
                                    scsi_pointer->buffer->length;
                                scsi_pointer->ptr =
                                        sg_virt(scsi_pointer->buffer);
                        }
                }
                /* Now check to see if the drive is ready to comunicate */
                r = (r_str(ppb) & 0xf0);
                /* If not, drop back down to the scheduler and wait a timer tick */
                if (!(r & 0x80))
                        return 0;
        }
        return 1;               /* FINISH_RETURN */
}

/*
 * Since the PPA 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 ppa_interrupt(struct work_struct *work)
{
        ppa_struct *dev = container_of(work, ppa_struct, ppa_tq.work);
        struct scsi_cmnd *cmd = dev->cur_cmd;

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

        if (ppa_scsi_pointer(cmd)->phase > 1)
                ppa_disconnect(dev);

        ppa_pb_dismiss(dev);

        dev->cur_cmd = NULL;

        scsi_done(cmd);
}

static int ppa_engine(ppa_struct *dev, struct scsi_cmnd *cmd)
{
        struct scsi_pointer *scsi_pointer = ppa_scsi_pointer(cmd);
        unsigned short ppb = dev->base;
        unsigned char l = 0, h = 0;
        int retv;

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

        switch (scsi_pointer->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
                         */
                        ppa_fail(dev, DID_BUS_BUSY);
                        return 0;
                }
                return 1;       /* wait until ppa_wakeup claims parport */
        case 1:         /* Phase 1 - Connected */
                {               /* Perform a sanity check for cable unplugged */
                        int retv = 2;   /* Failed */

                        ppa_connect(dev, CONNECT_EPP_MAYBE);

                        w_ctr(ppb, 0xe);
                        if ((r_str(ppb) & 0x08) == 0x08)
                                retv--;

                        w_ctr(ppb, 0xc);
                        if ((r_str(ppb) & 0x08) == 0x00)
                                retv--;

                        if (retv) {
                                if (time_after(jiffies, dev->jstart + (1 * HZ))) {
                                        printk(KERN_ERR "ppa: Parallel port cable is unplugged.\n");
                                        ppa_fail(dev, DID_BUS_BUSY);
                                        return 0;
                                } else {
                                        ppa_disconnect(dev);
                                        return 1;       /* Try again in a jiffy */
                                }
                        }
                        scsi_pointer->phase++;
                }
                fallthrough;

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

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

                if (!ppa_send_command(cmd))
                        return 0;
                scsi_pointer->phase++;
                fallthrough;

        case 4:         /* Phase 4 - Setup scatter/gather buffers */
                if (scsi_bufflen(cmd)) {
                        scsi_pointer->buffer = scsi_sglist(cmd);
                        scsi_pointer->this_residual =
                                scsi_pointer->buffer->length;
                        scsi_pointer->ptr = sg_virt(scsi_pointer->buffer);
                } else {
                        scsi_pointer->buffer = NULL;
                        scsi_pointer->this_residual = 0;
                        scsi_pointer->ptr = NULL;
                }
                scsi_pointer->buffers_residual = scsi_sg_count(cmd) - 1;
                scsi_pointer->phase++;
                fallthrough;

        case 5:         /* Phase 5 - Data transfer stage */
                w_ctr(ppb, 0x0c);
                if (!(r_str(ppb) & 0x80))
                        return 1;

                retv = ppa_completion(cmd);
                if (retv == -1)
                        return 0;
                if (retv == 0)
                        return 1;
                scsi_pointer->phase++;
                fallthrough;

        case 6:         /* Phase 6 - Read status/message */
                cmd->result = DID_OK << 16;
                /* Check for data overrun */
                if (ppa_wait(dev) != (unsigned char) 0xf0) {
                        ppa_fail(dev, DID_ERROR);
                        return 0;
                }
                if (ppa_in(dev, &l, 1)) {       /* read status byte */
                        /* Check for optional message byte */
                        if (ppa_wait(dev) == (unsigned char) 0xf0)
                                ppa_in(dev, &h, 1);
                        cmd->result =
                            (DID_OK << 16) + (h << 8) + (l & STATUS_MASK);
                }
                return 0;       /* Finished */

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

static enum scsi_qc_status ppa_queuecommand_lck(struct scsi_cmnd *cmd)
{
        ppa_struct *dev = ppa_dev(cmd->device->host);

        if (dev->cur_cmd) {
                printk(KERN_ERR "PPA: bug in ppa_queuecommand\n");
                return 0;
        }
        dev->failed = 0;
        dev->jstart = jiffies;
        dev->cur_cmd = cmd;
        cmd->result = DID_ERROR << 16;  /* default return code */
        ppa_scsi_pointer(cmd)->phase = 0;       /* bus free */

        schedule_delayed_work(&dev->ppa_tq, 0);

        ppa_pb_claim(dev);

        return 0;
}

static DEF_SCSI_QCMD(ppa_queuecommand)

/*
 * 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 ppa_biosparam(struct scsi_device *sdev, struct gendisk *unused,
              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]);
                if (ip[2] > 1023)
                        ip[2] = 1023;
        }
        return 0;
}

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

        switch (ppa_scsi_pointer(cmd)->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;
        default:                /* SCSI command sent, can not abort */
                return FAILED;
        }
}

static void ppa_reset_pulse(unsigned int base)
{
        w_dtr(base, 0x40);
        w_ctr(base, 0x8);
        udelay(30);
        w_ctr(base, 0xc);
}

static int ppa_reset(struct scsi_cmnd *cmd)
{
        ppa_struct *dev = ppa_dev(cmd->device->host);

        if (ppa_scsi_pointer(cmd)->phase)
                ppa_disconnect(dev);
        dev->cur_cmd = NULL;    /* Forget the problem */

        ppa_connect(dev, CONNECT_NORMAL);
        ppa_reset_pulse(dev->base);
        mdelay(1);              /* device settle delay */
        ppa_disconnect(dev);
        mdelay(1);              /* device settle delay */
        return SUCCESS;
}

static int device_check(ppa_struct *dev, bool autodetect)
{
        /* 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 u8 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 (autodetect && (ppb & 0x0007) == 0x0000)
                        dev->mode = PPA_EPP_8;

second_pass:
                ppa_connect(dev, CONNECT_EPP_MAYBE);
                /* Select SCSI device */
                if (!ppa_select(dev, loop)) {
                        ppa_disconnect(dev);
                        continue;
                }
                printk(KERN_INFO "ppa: Found device at ID %i, Attempting to use %s\n",
                       loop, PPA_MODE_STRING[dev->mode]);

                /* Send SCSI command */
                status = 1;
                w_ctr(ppb, 0x0c);
                for (l = 0; (l < 6) && (status); l++)
                        status = ppa_out(dev, cmd, 1);

                if (!status) {
                        ppa_disconnect(dev);
                        ppa_connect(dev, CONNECT_EPP_MAYBE);
                        w_dtr(ppb, 0x40);
                        w_ctr(ppb, 0x08);
                        udelay(30);
                        w_ctr(ppb, 0x0c);
                        udelay(1000);
                        ppa_disconnect(dev);
                        udelay(1000);
                        if (dev->mode != old_mode) {
                                dev->mode = old_mode;
                                goto second_pass;
                        }
                        return -EIO;
                }
                w_ctr(ppb, 0x0c);
                k = 1000000;    /* 1 Second */
                do {
                        l = r_str(ppb);
                        k--;
                        udelay(1);
                } while (!(l & 0x80) && (k));

                l &= 0xf0;

                if (l != 0xf0) {
                        ppa_disconnect(dev);
                        ppa_connect(dev, CONNECT_EPP_MAYBE);
                        ppa_reset_pulse(ppb);
                        udelay(1000);
                        ppa_disconnect(dev);
                        udelay(1000);
                        if (dev->mode != old_mode) {
                                dev->mode = old_mode;
                                goto second_pass;
                        }
                        return -EIO;
                }
                ppa_disconnect(dev);
                printk(KERN_INFO "ppa: Communication established with ID %i using %s\n",
                       loop, PPA_MODE_STRING[dev->mode]);
                ppa_connect(dev, CONNECT_EPP_MAYBE);
                ppa_reset_pulse(ppb);
                udelay(1000);
                ppa_disconnect(dev);
                udelay(1000);
                return 0;
        }
        return -ENODEV;
}

static const struct scsi_host_template ppa_template = {
        .module                 = THIS_MODULE,
        .proc_name              = "ppa",
        .show_info              = ppa_show_info,
        .write_info             = ppa_write_info,
        .name                   = "Iomega VPI0 (ppa) interface",
        .queuecommand           = ppa_queuecommand,
        .eh_abort_handler       = ppa_abort,
        .eh_host_reset_handler  = ppa_reset,
        .bios_param             = ppa_biosparam,
        .this_id                = -1,
        .sg_tablesize           = SG_ALL,
        .can_queue              = 1,
        .cmd_size               = sizeof(struct scsi_pointer),
};

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

static LIST_HEAD(ppa_hosts);

/*
 * Finds the first available device number that can be alloted to the
 * new ppa device and returns the address of the previous node so that
 * we can add to the tail and have a list in the ascending order.
 */

static inline ppa_struct *find_parent(void)
{
        ppa_struct *dev, *par = NULL;
        unsigned int cnt = 0;

        if (list_empty(&ppa_hosts))
                return NULL;

        list_for_each_entry(dev, &ppa_hosts, list) {
                if (dev->dev_no != cnt)
                        return par;
                cnt++;
                par = dev;
        }

        return par;
}

static int __ppa_attach(struct parport *pb)
{
        struct Scsi_Host *host;
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(waiting);
        DEFINE_WAIT(wait);
        ppa_struct *dev, *temp;
        int ports;
        int err = -ENOMEM;
        struct pardev_cb ppa_cb;

        dev = kzalloc_obj(ppa_struct);
        if (!dev)
                return -ENOMEM;
        dev->base = -1;
        dev->mode = mode < PPA_UNKNOWN ? mode : PPA_AUTODETECT;
        dev->recon_tmo = PPA_RECON_TMO;
        init_waitqueue_head(&waiting);
        temp = find_parent();
        if (temp)
                dev->dev_no = temp->dev_no + 1;

        memset(&ppa_cb, 0, sizeof(ppa_cb));
        ppa_cb.private = dev;
        ppa_cb.wakeup = ppa_wakeup;

        dev->dev = parport_register_dev_model(pb, "ppa", &ppa_cb, dev->dev_no);

        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 (ppa_pb_claim(dev))
                schedule_timeout(3 * HZ);
        if (dev->wanted) {
                printk(KERN_ERR "ppa%d: failed to claim parport because "
                                "a pardevice is owning the port for too long "
                                "time!\n", pb->number);
                ppa_pb_dismiss(dev);
                dev->waiting = NULL;
                finish_wait(&waiting, &wait);
                goto out1;
        }
        dev->waiting = NULL;
        finish_wait(&waiting, &wait);
        dev->base = dev->dev->port->base;
        w_ctr(dev->base, 0x0c);

        /* Done configuration */

        err = ppa_init(dev);
        ppa_pb_release(dev);

        if (err)
                goto out1;

        /* now the glue ... */
        if (dev->mode == PPA_NIBBLE || dev->mode == PPA_PS2)
                ports = 3;
        else
                ports = 8;

        INIT_DELAYED_WORK(&dev->ppa_tq, ppa_interrupt);

        err = -ENOMEM;
        host = scsi_host_alloc(&ppa_template, sizeof(ppa_struct *));
        if (!host)
                goto out1;
        host->io_port = pb->base;
        host->n_io_port = ports;
        host->dma_channel = -1;
        host->unique_id = pb->number;
        *(ppa_struct **)&host->hostdata = dev;
        dev->host = host;
        list_add_tail(&dev->list, &ppa_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 ppa_attach(struct parport *pb)
{
        __ppa_attach(pb);
}

static void ppa_detach(struct parport *pb)
{
        ppa_struct *dev;
        list_for_each_entry(dev, &ppa_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 ppa_driver = {
        .name           = "ppa",
        .match_port     = ppa_attach,
        .detach         = ppa_detach,
};
module_parport_driver(ppa_driver);

MODULE_DESCRIPTION("IOMEGA PPA3 parallel port SCSI host adapter driver");
MODULE_LICENSE("GPL");