Import 2.3.9pre5

[davej-history.git] / drivers / block / cmd640.c

/*
 *  linux/drivers/block/cmd640.c        Version 1.02  Sep 01, 1996
 *
 *  Copyright (C) 1995-1996  Linus Torvalds & authors (see below)
 */

/*
 *  Original authors:   abramov@cecmow.enet.dec.com (Igor Abramov)
 *                      mlord@pobox.com (Mark Lord)
 *
 *  See linux/MAINTAINERS for address of current maintainer.
 *
 *  This file provides support for the advanced features and bugs
 *  of IDE interfaces using the CMD Technologies 0640 IDE interface chip.
 *
 *  These chips are basically fucked by design, and getting this driver
 *  to work on every motherboard design that uses this screwed chip seems
 *  bloody well impossible.  However, we're still trying.
 *
 *  Version 0.97 worked for everybody.
 *
 *  User feedback is essential.  Many thanks to the beta test team:
 *
 *  A.Hartgers@stud.tue.nl, JZDQC@CUNYVM.CUNY.edu, abramov@cecmow.enet.dec.com,
 *  bardj@utopia.ppp.sn.no, bart@gaga.tue.nl, bbol001@cs.auckland.ac.nz,
 *  chrisc@dbass.demon.co.uk, dalecki@namu26.Num.Math.Uni-Goettingen.de,
 *  derekn@vw.ece.cmu.edu, florian@btp2x3.phy.uni-bayreuth.de,
 *  flynn@dei.unipd.it, gadio@netvision.net.il, godzilla@futuris.net,
 *  j@pobox.com, jkemp1@mises.uni-paderborn.de, jtoppe@hiwaay.net,
 *  kerouac@ssnet.com, meskes@informatik.rwth-aachen.de, hzoli@cs.elte.hu,
 *  peter@udgaard.isgtec.com, phil@tazenda.demon.co.uk, roadcapw@cfw.com,
 *  s0033las@sun10.vsz.bme.hu, schaffer@tam.cornell.edu, sjd@slip.net,
 *  steve@ei.org, ulrpeg@bigcomm.gun.de, ism@tardis.ed.ac.uk, mack@cray.com
 *  liug@mama.indstate.edu, and others.
 *
 *  Version 0.01        Initial version, hacked out of ide.c,
 *                      and #include'd rather than compiled separately.
 *                      This will get cleaned up in a subsequent release.
 *
 *  Version 0.02        Fixes for vlb initialization code, enable prefetch
 *                      for versions 'B' and 'C' of chip by default,
 *                      some code cleanup.
 *
 *  Version 0.03        Added reset of secondary interface,
 *                      and black list for devices which are not compatible
 *                      with prefetch mode. Separate function for setting
 *                      prefetch is added, possibly it will be called some
 *                      day from ioctl processing code.
 *
 *  Version 0.04        Now configs/compiles separate from ide.c
 *
 *  Version 0.05        Major rewrite of interface timing code.
 *                      Added new function cmd640_set_mode to set PIO mode
 *                      from ioctl call. New drives added to black list.
 *
 *  Version 0.06        More code cleanup. Prefetch is enabled only for
 *                      detected hard drives, not included in prefetch
 *                      black list.
 *
 *  Version 0.07        Changed to more conservative drive tuning policy.
 *                      Unknown drives, which report PIO < 4 are set to
 *                      (reported_PIO - 1) if it is supported, or to PIO0.
 *                      List of known drives extended by info provided by
 *                      CMD at their ftp site.
 *
 *  Version 0.08        Added autotune/noautotune support.
 *
 *  Version 0.09        Try to be smarter about 2nd port enabling.
 *  Version 0.10        Be nice and don't reset 2nd port.
 *  Version 0.11        Try to handle more wierd situations.
 *
 *  Version 0.12        Lots of bug fixes from Laszlo Peter
 *                      irq unmasking disabled for reliability.
 *                      try to be even smarter about the second port.
 *                      tidy up source code formatting.
 *  Version 0.13        permit irq unmasking again.
 *  Version 0.90        massive code cleanup, some bugs fixed.
 *                      defaults all drives to PIO mode0, prefetch off.
 *                      autotune is OFF by default, with compile time flag.
 *                      prefetch can be turned OFF/ON using "hdparm -p8/-p9"
 *                       (requires hdparm-3.1 or newer)
 *  Version 0.91        first release to linux-kernel list.
 *  Version 0.92        move initial reg dump to separate callable function
 *                      change "readahead" to "prefetch" to avoid confusion
 *  Version 0.95        respect original BIOS timings unless autotuning.
 *                      tons of code cleanup and rearrangement.
 *                      added CONFIG_BLK_DEV_CMD640_ENHANCED option
 *                      prevent use of unmask when prefetch is on
 *  Version 0.96        prevent use of io_32bit when prefetch is off
 *  Version 0.97        fix VLB secondary interface for sjd@slip.net
 *                      other minor tune-ups:  0.96 was very good.
 *  Version 0.98        ignore PCI version when disabled by BIOS
 *  Version 0.99        display setup/active/recovery clocks with PIO mode
 *  Version 1.00        Mmm.. cannot depend on PCMD_ENA in all systems
 *  Version 1.01        slow/fast devsel can be selected with "hdparm -p6/-p7"
 *                       ("fast" is necessary for 32bit I/O in some systems)
 *  Version 1.02        fix bug that resulted in slow "setup times"
 *                       (patch courtesy of Zoltan Hidvegi)
 */

#undef REALLY_SLOW_IO           /* most systems can safely undef this */
#define CMD640_PREFETCH_MASKS 1

#include <linux/config.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/blkdev.h>
#include <linux/hdreg.h>
#include <linux/ide.h>

#include <asm/io.h>

#include "ide_modes.h"

/*
 * This flag is set in ide.c by the parameter:  ide0=cmd640_vlb
 */
int cmd640_vlb = 0;

/*
 * CMD640 specific registers definition.
 */

#define VID             0x00
#define DID             0x02
#define PCMD            0x04
#define   PCMD_ENA      0x01
#define PSTTS           0x06
#define REVID           0x08
#define PROGIF          0x09
#define SUBCL           0x0a
#define BASCL           0x0b
#define BaseA0          0x10
#define BaseA1          0x14
#define BaseA2          0x18
#define BaseA3          0x1c
#define INTLINE         0x3c
#define INPINE          0x3d

#define CFR             0x50
#define   CFR_DEVREV            0x03
#define   CFR_IDE01INTR         0x04
#define   CFR_DEVID             0x18
#define   CFR_AT_VESA_078h      0x20
#define   CFR_DSA1              0x40
#define   CFR_DSA0              0x80

#define CNTRL           0x51
#define   CNTRL_DIS_RA0         0x40
#define   CNTRL_DIS_RA1         0x80
#define   CNTRL_ENA_2ND         0x08

#define CMDTIM          0x52
#define ARTTIM0         0x53
#define DRWTIM0         0x54
#define ARTTIM1         0x55
#define DRWTIM1         0x56
#define ARTTIM23        0x57
#define   ARTTIM23_DIS_RA2      0x04
#define   ARTTIM23_DIS_RA3      0x08
#define DRWTIM23        0x58
#define BRST            0x59

/*
 * Registers and masks for easy access by drive index:
 */
static byte prefetch_regs[4]  = {CNTRL, CNTRL, ARTTIM23, ARTTIM23};
static byte prefetch_masks[4] = {CNTRL_DIS_RA0, CNTRL_DIS_RA1, ARTTIM23_DIS_RA2, ARTTIM23_DIS_RA3};

#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED

static byte arttim_regs[4] = {ARTTIM0, ARTTIM1, ARTTIM23, ARTTIM23};
static byte drwtim_regs[4] = {DRWTIM0, DRWTIM1, DRWTIM23, DRWTIM23};

/*
 * Current cmd640 timing values for each drive.
 * The defaults for each are the slowest possible timings.
 */
static byte setup_counts[4]    = {4, 4, 4, 4};     /* Address setup count (in clocks) */
static byte active_counts[4]   = {16, 16, 16, 16}; /* Active count   (encoded) */
static byte recovery_counts[4] = {16, 16, 16, 16}; /* Recovery count (encoded) */

#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */

/*
 * These are initialized to point at the devices we control
 */
static ide_hwif_t  *cmd_hwif0, *cmd_hwif1;
static ide_drive_t *cmd_drives[4];

/*
 * Interface to access cmd640x registers
 */
static unsigned int cmd640_key;
static void (*put_cmd640_reg)(unsigned short reg, byte val);
static byte (*get_cmd640_reg)(unsigned short reg);

/*
 * This is read from the CFR reg, and is used in several places.
 */
static unsigned int cmd640_chip_version;

/*
 * The CMD640x chip does not support DWORD config write cycles, but some
 * of the BIOSes use them to implement the config services.
 * Therefore, we must use direct IO instead.
 */

/* PCI method 1 access */

static void put_cmd640_reg_pci1 (unsigned short reg, byte val)
{
        unsigned long flags;

        save_flags(flags);
        cli();
        outl_p((reg & 0xfc) | cmd640_key, 0xcf8);
        outb_p(val, (reg & 3) | 0xcfc);
        restore_flags(flags);
}

static byte get_cmd640_reg_pci1 (unsigned short reg)
{
        byte b;
        unsigned long flags;

        save_flags(flags);
        cli();
        outl_p((reg & 0xfc) | cmd640_key, 0xcf8);
        b = inb_p((reg & 3) | 0xcfc);
        restore_flags(flags);
        return b;
}

/* PCI method 2 access (from CMD datasheet) */

static void put_cmd640_reg_pci2 (unsigned short reg, byte val)
{
        unsigned long flags;

        save_flags(flags);
        cli();
        outb_p(0x10, 0xcf8);
        outb_p(val, cmd640_key + reg);
        outb_p(0, 0xcf8);
        restore_flags(flags);
}

static byte get_cmd640_reg_pci2 (unsigned short reg)
{
        byte b;
        unsigned long flags;

        save_flags(flags);
        cli();
        outb_p(0x10, 0xcf8);
        b = inb_p(cmd640_key + reg);
        outb_p(0, 0xcf8);
        restore_flags(flags);
        return b;
}

/* VLB access */

static void put_cmd640_reg_vlb (unsigned short reg, byte val)
{
        unsigned long flags;

        save_flags(flags);
        cli();
        outb_p(reg, cmd640_key);
        outb_p(val, cmd640_key + 4);
        restore_flags(flags);
}

static byte get_cmd640_reg_vlb (unsigned short reg)
{
        byte b;
        unsigned long flags;

        save_flags(flags);
        cli();
        outb_p(reg, cmd640_key);
        b = inb_p(cmd640_key + 4);
        restore_flags(flags);
        return b;
}

static int match_pci_cmd640_device (void)
{
        const byte ven_dev[4] = {0x95, 0x10, 0x40, 0x06};
        unsigned int i;
        for (i = 0; i < 4; i++) {
                if (get_cmd640_reg(i) != ven_dev[i])
                        return 0;
        }
#ifdef STUPIDLY_TRUST_BROKEN_PCMD_ENA_BIT
        if ((get_cmd640_reg(PCMD) & PCMD_ENA) == 0) {
                printk("ide: cmd640 on PCI disabled by BIOS\n");
                return 0;
        }
#endif /* STUPIDLY_TRUST_BROKEN_PCMD_ENA_BIT */
        return 1; /* success */
}

/*
 * Probe for CMD640x -- pci method 1
 */
static int probe_for_cmd640_pci1 (void)
{
        get_cmd640_reg = get_cmd640_reg_pci1;
        put_cmd640_reg = put_cmd640_reg_pci1;
        for (cmd640_key = 0x80000000; cmd640_key <= 0x8000f800; cmd640_key += 0x800) {
                if (match_pci_cmd640_device())
                        return 1; /* success */
        }
        return 0;
}

/*
 * Probe for CMD640x -- pci method 2
 */
static int probe_for_cmd640_pci2 (void)
{
        get_cmd640_reg = get_cmd640_reg_pci2;
        put_cmd640_reg = put_cmd640_reg_pci2;
        for (cmd640_key = 0xc000; cmd640_key <= 0xcf00; cmd640_key += 0x100) {
                if (match_pci_cmd640_device())
                        return 1; /* success */
        }
        return 0;
}

/*
 * Probe for CMD640x -- vlb
 */
static int probe_for_cmd640_vlb (void)
{
        byte b;

        get_cmd640_reg = get_cmd640_reg_vlb;
        put_cmd640_reg = put_cmd640_reg_vlb;
        cmd640_key = 0x178;
        b = get_cmd640_reg(CFR);
        if (b == 0xff || b == 0x00 || (b & CFR_AT_VESA_078h)) {
                cmd640_key = 0x78;
                b = get_cmd640_reg(CFR);
                if (b == 0xff || b == 0x00 || !(b & CFR_AT_VESA_078h))
                        return 0;
        }
        return 1; /* success */
}

/*
 *  Returns 1 if an IDE interface/drive exists at 0x170,
 *  Returns 0 otherwise.
 */
static int secondary_port_responding (void)
{
        unsigned long flags;

        save_flags(flags);
        cli();

        outb_p(0x0a, 0x170 + IDE_SELECT_OFFSET);        /* select drive0 */
        udelay(100);
        if ((inb_p(0x170 + IDE_SELECT_OFFSET) & 0x1f) != 0x0a) {
                outb_p(0x1a, 0x170 + IDE_SELECT_OFFSET); /* select drive1 */
                udelay(100);
                if ((inb_p(0x170 + IDE_SELECT_OFFSET) & 0x1f) != 0x1a) {
                        restore_flags(flags);
                        return 0; /* nothing responded */
                }
        }
        restore_flags(flags);
        return 1; /* success */
}

#ifdef CMD640_DUMP_REGS
/*
 * Dump out all cmd640 registers.  May be called from ide.c
 */
void cmd640_dump_regs (void)
{
        unsigned int reg = cmd640_vlb ? 0x50 : 0x00;

        /* Dump current state of chip registers */
        printk("ide: cmd640 internal register dump:");
        for (; reg <= 0x59; reg++) {
                if (!(reg & 0x0f))
                        printk("\n%04x:", reg);
                printk(" %02x", get_cmd640_reg(reg));
        }
        printk("\n");
}
#endif

/*
 * Check whether prefetch is on for a drive,
 * and initialize the unmask flags for safe operation.
 */
static void check_prefetch (unsigned int index)
{
        ide_drive_t *drive = cmd_drives[index];
        byte b = get_cmd640_reg(prefetch_regs[index]);

        if (b & prefetch_masks[index]) {        /* is prefetch off? */
                drive->no_unmask = 0;
                drive->no_io_32bit = 1;
                drive->io_32bit = 0;
        } else {
#if CMD640_PREFETCH_MASKS
                drive->no_unmask = 1;
                drive->unmask = 0;
#endif
                drive->no_io_32bit = 0;
        }
}

/*
 * Figure out which devices we control
 */
static void setup_device_ptrs (void)
{
        unsigned int i;

        cmd_hwif0 = &ide_hwifs[0]; /* default, if not found below */
        cmd_hwif1 = &ide_hwifs[1]; /* default, if not found below */
        for (i = 0; i < MAX_HWIFS; i++) {
                ide_hwif_t *hwif = &ide_hwifs[i];
                if (hwif->chipset == ide_unknown || hwif->chipset == ide_generic) {
                        if (hwif->io_ports[IDE_DATA_OFFSET] == 0x1f0)
                                cmd_hwif0 = hwif;
                        else if (hwif->io_ports[IDE_DATA_OFFSET] == 0x170)
                                cmd_hwif1 = hwif;
                }
        }
        cmd_drives[0] = &cmd_hwif0->drives[0];
        cmd_drives[1] = &cmd_hwif0->drives[1];
        cmd_drives[2] = &cmd_hwif1->drives[0];
        cmd_drives[3] = &cmd_hwif1->drives[1];
}

#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED

/*
 * Sets prefetch mode for a drive.
 */
static void set_prefetch_mode (unsigned int index, int mode)
{
        ide_drive_t *drive = cmd_drives[index];
        int reg = prefetch_regs[index];
        byte b;
        unsigned long flags;

        save_flags(flags);
        cli();
        b = get_cmd640_reg(reg);
        if (mode) {     /* want prefetch on? */
#if CMD640_PREFETCH_MASKS
                drive->no_unmask = 1;
                drive->unmask = 0;
#endif
                drive->no_io_32bit = 0;
                b &= ~prefetch_masks[index];    /* enable prefetch */
        } else {
                drive->no_unmask = 0;
                drive->no_io_32bit = 1;
                drive->io_32bit = 0;
                b |= prefetch_masks[index];     /* disable prefetch */
        }
        put_cmd640_reg(reg, b);
        restore_flags(flags);
}

/*
 * Dump out current drive clocks settings
 */
static void display_clocks (unsigned int index)
{
        byte active_count, recovery_count;

        active_count = active_counts[index];
        if (active_count == 1)
                ++active_count;
        recovery_count = recovery_counts[index];
        if (active_count > 3 && recovery_count == 1)
                ++recovery_count;
        if (cmd640_chip_version > 1)
                recovery_count += 1;  /* cmd640b uses (count + 1)*/
        printk(", clocks=%d/%d/%d\n", setup_counts[index], active_count, recovery_count);
}

/*
 * Pack active and recovery counts into single byte representation
 * used by controller
 */
inline static byte pack_nibbles (byte upper, byte lower)
{
        return ((upper & 0x0f) << 4) | (lower & 0x0f);
}

/*
 * This routine retrieves the initial drive timings from the chipset.
 */
static void retrieve_drive_counts (unsigned int index)
{
        byte b;

        /*
         * Get the internal setup timing, and convert to clock count
         */
        b = get_cmd640_reg(arttim_regs[index]) & ~0x3f;
        switch (b) {
                case 0x00: b = 4; break;
                case 0x80: b = 3; break;
                case 0x40: b = 2; break;
                default:   b = 5; break;
        }
        setup_counts[index] = b;

        /*
         * Get the active/recovery counts
         */
        b = get_cmd640_reg(drwtim_regs[index]);
        active_counts[index]   = (b >> 4)   ? (b >> 4)   : 0x10;
        recovery_counts[index] = (b & 0x0f) ? (b & 0x0f) : 0x10;
}


/*
 * This routine writes the prepared setup/active/recovery counts
 * for a drive into the cmd640 chipset registers to active them.
 */
static void program_drive_counts (unsigned int index)
{
        unsigned long flags;
        byte setup_count    = setup_counts[index];
        byte active_count   = active_counts[index];
        byte recovery_count = recovery_counts[index];

        /*
         * Set up address setup count and drive read/write timing registers.
         * Primary interface has individual count/timing registers for
         * each drive.  Secondary interface has one common set of registers,
         * so we merge the timings, using the slowest value for each timing.
         */
        if (index > 1) {
                unsigned int mate;
                if (cmd_drives[mate = index ^ 1]->present) {
                        if (setup_count < setup_counts[mate])
                                setup_count = setup_counts[mate];
                        if (active_count < active_counts[mate])
                                active_count = active_counts[mate];
                        if (recovery_count < recovery_counts[mate])
                                recovery_count = recovery_counts[mate];
                }
        }

        /*
         * Convert setup_count to internal chipset representation
         */
        switch (setup_count) {
                case 4:  setup_count = 0x00; break;
                case 3:  setup_count = 0x80; break;
                case 1:
                case 2:  setup_count = 0x40; break;
                default: setup_count = 0xc0; /* case 5 */
        }

        /*
         * Now that everything is ready, program the new timings
         */
        save_flags (flags);
        cli();
        /*
         * Program the address_setup clocks into ARTTIM reg,
         * and then the active/recovery counts into the DRWTIM reg
         * (this converts counts of 16 into counts of zero -- okay).
         */
        setup_count |= get_cmd640_reg(arttim_regs[index]) & 0x3f;
        put_cmd640_reg(arttim_regs[index], setup_count);
        put_cmd640_reg(drwtim_regs[index], pack_nibbles(active_count, recovery_count));
        restore_flags(flags);
}

/*
 * Set a specific pio_mode for a drive
 */
static void cmd640_set_mode (unsigned int index, byte pio_mode, unsigned int cycle_time)
{
        int setup_time, active_time, recovery_time, clock_time;
        byte setup_count, active_count, recovery_count, recovery_count2, cycle_count;
        int bus_speed = ide_system_bus_speed();

        if (pio_mode > 5)
                pio_mode = 5;
        setup_time  = ide_pio_timings[pio_mode].setup_time;
        active_time = ide_pio_timings[pio_mode].active_time;
        recovery_time = cycle_time - (setup_time + active_time);
        clock_time = 1000 / bus_speed;
        cycle_count = (cycle_time + clock_time - 1) / clock_time;

        setup_count = (setup_time + clock_time - 1) / clock_time;

        active_count = (active_time + clock_time - 1) / clock_time;
        if (active_count < 2)
                active_count = 2; /* minimum allowed by cmd640 */

        recovery_count = (recovery_time + clock_time - 1) / clock_time;
        recovery_count2 = cycle_count - (setup_count + active_count);
        if (recovery_count2 > recovery_count)
                recovery_count = recovery_count2;
        if (recovery_count < 2)
                recovery_count = 2; /* minimum allowed by cmd640 */
        if (recovery_count > 17) {
                active_count += recovery_count - 17;
                recovery_count = 17;
        }
        if (active_count > 16)
                active_count = 16; /* maximum allowed by cmd640 */
        if (cmd640_chip_version > 1)
                recovery_count -= 1;  /* cmd640b uses (count + 1)*/
        if (recovery_count > 16)
                recovery_count = 16; /* maximum allowed by cmd640 */

        setup_counts[index]    = setup_count;
        active_counts[index]   = active_count;
        recovery_counts[index] = recovery_count;

        /*
         * In a perfect world, we might set the drive pio mode here
         * (using WIN_SETFEATURE) before continuing.
         *
         * But we do not, because:
         *      1) this is the wrong place to do it (proper is do_special() in ide.c)
         *      2) in practice this is rarely, if ever, necessary
         */
        program_drive_counts (index);
}

/*
 * Drive PIO mode selection:
 */
static void cmd640_tune_drive (ide_drive_t *drive, byte mode_wanted)
{
        byte b;
        ide_pio_data_t  d;
        unsigned int index = 0;

        while (drive != cmd_drives[index]) {
                if (++index > 3) {
                        printk("%s: bad news in cmd640_tune_drive\n", drive->name);
                        return;
                }
        }
        switch (mode_wanted) {
                case 6: /* set fast-devsel off */
                case 7: /* set fast-devsel on */
                        mode_wanted &= 1;
                        b = get_cmd640_reg(CNTRL) & ~0x27;
                        if (mode_wanted)
                                b |= 0x27;
                        put_cmd640_reg(CNTRL, b);
                        printk("%s: %sabled cmd640 fast host timing (devsel)\n", drive->name, mode_wanted ? "en" : "dis");
                        return;

                case 8: /* set prefetch off */
                case 9: /* set prefetch on */
                        mode_wanted &= 1;
                        set_prefetch_mode(index, mode_wanted);
                        printk("%s: %sabled cmd640 prefetch\n", drive->name, mode_wanted ? "en" : "dis");
                        return;
        }

        (void) ide_get_best_pio_mode (drive, mode_wanted, 5, &d);
        cmd640_set_mode (index, d.pio_mode, d.cycle_time);

        printk ("%s: selected cmd640 PIO mode%d (%dns)%s",
                drive->name,
                d.pio_mode,
                d.cycle_time,
                d.overridden ? " (overriding vendor mode)" : "");
        display_clocks(index);
}

#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */

/*
 * Probe for a cmd640 chipset, and initialize it if found.  Called from ide.c
 */
int ide_probe_for_cmd640x (void)
{
#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED
        int second_port_toggled = 0;
#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */
        int second_port_cmd640 = 0;
        const char *bus_type, *port2;
        unsigned int index;
        byte b, cfr;

        if (cmd640_vlb && probe_for_cmd640_vlb()) {
                bus_type = "VLB";
        } else {
                cmd640_vlb = 0;
                if (probe_for_cmd640_pci1())
                        bus_type = "PCI (type1)";
                else if (probe_for_cmd640_pci2())
                        bus_type = "PCI (type2)";
                else
                        return 0;
        }
        /*
         * Undocumented magic (there is no 0x5b reg in specs)
         */
        put_cmd640_reg(0x5b, 0xbd);
        if (get_cmd640_reg(0x5b) != 0xbd) {
                printk("ide: cmd640 init failed: wrong value in reg 0x5b\n");
                return 0;
        }
        put_cmd640_reg(0x5b, 0);

#ifdef CMD640_DUMP_REGS
        CMD640_DUMP_REGS;
#endif

        /*
         * Documented magic begins here
         */
        cfr = get_cmd640_reg(CFR);
        cmd640_chip_version = cfr & CFR_DEVREV;
        if (cmd640_chip_version == 0) {
                printk ("ide: bad cmd640 revision: %d\n", cmd640_chip_version);
                return 0;
        }

        /*
         * Initialize data for primary port
         */
        setup_device_ptrs ();
        printk("%s: buggy cmd640%c interface on %s, config=0x%02x\n",
               cmd_hwif0->name, 'a' + cmd640_chip_version - 1, bus_type, cfr);
        cmd_hwif0->chipset = ide_cmd640;
#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED
        cmd_hwif0->tuneproc = &cmd640_tune_drive;
#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */

        /*
         * Ensure compatibility by always using the slowest timings
         * for access to the drive's command register block,
         * and reset the prefetch burstsize to default (512 bytes).
         *
         * Maybe we need a way to NOT do these on *some* systems?
         */
        put_cmd640_reg(CMDTIM, 0);
        put_cmd640_reg(BRST, 0x40);

        /*
         * Try to enable the secondary interface, if not already enabled
         */
        if (cmd_hwif1->noprobe) {
                port2 = "not probed";
        } else {
                b = get_cmd640_reg(CNTRL);
                if (secondary_port_responding()) {
                        if ((b & CNTRL_ENA_2ND)) {
                                second_port_cmd640 = 1;
                                port2 = "okay";
                        } else if (cmd640_vlb) {
                                second_port_cmd640 = 1;
                                port2 = "alive";
                        } else
                                port2 = "not cmd640";
                } else {
                        put_cmd640_reg(CNTRL, b ^ CNTRL_ENA_2ND); /* toggle the bit */
                        if (secondary_port_responding()) {
                                second_port_cmd640 = 1;
#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED
                                second_port_toggled = 1;
#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */
                                port2 = "enabled";
                        } else {
                                put_cmd640_reg(CNTRL, b); /* restore original setting */
                                port2 = "not responding";
                        }
                }
        }

        /*
         * Initialize data for secondary cmd640 port, if enabled
         */
        if (second_port_cmd640) {
                cmd_hwif0->serialized = 1;
                cmd_hwif1->serialized = 1;
                cmd_hwif1->chipset = ide_cmd640;
                cmd_hwif0->mate = cmd_hwif1;
                cmd_hwif1->mate = cmd_hwif0;
                cmd_hwif1->channel = 1;
#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED
                cmd_hwif1->tuneproc = &cmd640_tune_drive;
#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */
        }
        printk("%s: %sserialized, secondary interface %s\n", cmd_hwif1->name,
                cmd_hwif0->serialized ? "" : "not ", port2);

        /*
         * Establish initial timings/prefetch for all drives.
         * Do not unnecessarily disturb any prior BIOS setup of these.
         */
        for (index = 0; index < (2 + (second_port_cmd640 << 1)); index++) {
                ide_drive_t *drive = cmd_drives[index];
#ifdef CONFIG_BLK_DEV_CMD640_ENHANCED
                if (drive->autotune || ((index > 1) && second_port_toggled)) {
                        /*
                         * Reset timing to the slowest speed and turn off prefetch.
                         * This way, the drive identify code has a better chance.
                         */
                        setup_counts    [index] = 4;    /* max possible */
                        active_counts   [index] = 16;   /* max possible */
                        recovery_counts [index] = 16;   /* max possible */
                        program_drive_counts (index);
                        set_prefetch_mode (index, 0);
                        printk("cmd640: drive%d timings/prefetch cleared\n", index);
                } else {
                        /*
                         * Record timings/prefetch without changing them.
                         * This preserves any prior BIOS setup.
                         */
                        retrieve_drive_counts (index);
                        check_prefetch (index);
                        printk("cmd640: drive%d timings/prefetch(%s) preserved",
                                index, drive->no_io_32bit ? "off" : "on");
                        display_clocks(index);
                }
#else
                /*
                 * Set the drive unmask flags to match the prefetch setting
                 */
                check_prefetch (index);
                printk("cmd640: drive%d timings/prefetch(%s) preserved\n",
                        index, drive->no_io_32bit ? "off" : "on");
#endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */
        }

#ifdef CMD640_DUMP_REGS
        CMD640_DUMP_REGS;
#endif
        return 1;
}