irqchip: crossbar: Introduce centralized check for crossbar write

[linux/fpc-iii.git] / drivers / scsi / sym53c8xx_2 / sym_nvram.c

/*
 * Device driver for the SYMBIOS/LSILOGIC 53C8XX and 53C1010 family 
 * of PCI-SCSI IO processors.
 *
 * Copyright (C) 1999-2001  Gerard Roudier <groudier@free.fr>
 *
 * This driver is derived from the Linux sym53c8xx driver.
 * Copyright (C) 1998-2000  Gerard Roudier
 *
 * The sym53c8xx driver is derived from the ncr53c8xx driver that had been 
 * a port of the FreeBSD ncr driver to Linux-1.2.13.
 *
 * The original ncr driver has been written for 386bsd and FreeBSD by
 *         Wolfgang Stanglmeier        <wolf@cologne.de>
 *         Stefan Esser                <se@mi.Uni-Koeln.de>
 * Copyright (C) 1994  Wolfgang Stanglmeier
 *
 * Other major contributions:
 *
 * NVRAM detection and reading.
 * Copyright (C) 1997 Richard Waltham <dormouse@farsrobt.demon.co.uk>
 *
 *-----------------------------------------------------------------------------
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "sym_glue.h"
#include "sym_nvram.h"

#ifdef  SYM_CONF_DEBUG_NVRAM
static u_char Tekram_boot_delay[7] = {3, 5, 10, 20, 30, 60, 120};
#endif

/*
 *  Get host setup from NVRAM.
 */
void sym_nvram_setup_host(struct Scsi_Host *shost, struct sym_hcb *np, struct sym_nvram *nvram)
{
        /*
         *  Get parity checking, host ID, verbose mode 
         *  and miscellaneous host flags from NVRAM.
         */
        switch (nvram->type) {
        case SYM_SYMBIOS_NVRAM:
                if (!(nvram->data.Symbios.flags & SYMBIOS_PARITY_ENABLE))
                        np->rv_scntl0  &= ~0x0a;
                np->myaddr = nvram->data.Symbios.host_id & 0x0f;
                if (nvram->data.Symbios.flags & SYMBIOS_VERBOSE_MSGS)
                        np->verbose += 1;
                if (nvram->data.Symbios.flags1 & SYMBIOS_SCAN_HI_LO)
                        shost->reverse_ordering = 1;
                if (nvram->data.Symbios.flags2 & SYMBIOS_AVOID_BUS_RESET)
                        np->usrflags |= SYM_AVOID_BUS_RESET;
                break;
        case SYM_TEKRAM_NVRAM:
                np->myaddr = nvram->data.Tekram.host_id & 0x0f;
                break;
#ifdef CONFIG_PARISC
        case SYM_PARISC_PDC:
                if (nvram->data.parisc.host_id != -1)
                        np->myaddr = nvram->data.parisc.host_id;
                if (nvram->data.parisc.factor != -1)
                        np->minsync = nvram->data.parisc.factor;
                if (nvram->data.parisc.width != -1)
                        np->maxwide = nvram->data.parisc.width;
                switch (nvram->data.parisc.mode) {
                        case 0: np->scsi_mode = SMODE_SE; break;
                        case 1: np->scsi_mode = SMODE_HVD; break;
                        case 2: np->scsi_mode = SMODE_LVD; break;
                        default: break;
                }
#endif
        default:
                break;
        }
}

/*
 *  Get target set-up from Symbios format NVRAM.
 */
static void
sym_Symbios_setup_target(struct sym_tcb *tp, int target, Symbios_nvram *nvram)
{
        Symbios_target *tn = &nvram->target[target];

        if (!(tn->flags & SYMBIOS_QUEUE_TAGS_ENABLED))
                tp->usrtags = 0;
        if (!(tn->flags & SYMBIOS_DISCONNECT_ENABLE))
                tp->usrflags &= ~SYM_DISC_ENABLED;
        if (!(tn->flags & SYMBIOS_SCAN_AT_BOOT_TIME))
                tp->usrflags |= SYM_SCAN_BOOT_DISABLED;
        if (!(tn->flags & SYMBIOS_SCAN_LUNS))
                tp->usrflags |= SYM_SCAN_LUNS_DISABLED;
        tp->usr_period = (tn->sync_period + 3) / 4;
        tp->usr_width = (tn->bus_width == 0x8) ? 0 : 1;
}

static const unsigned char Tekram_sync[16] = {
        25, 31, 37, 43, 50, 62, 75, 125, 12, 15, 18, 21, 6, 7, 9, 10
};

/*
 *  Get target set-up from Tekram format NVRAM.
 */
static void
sym_Tekram_setup_target(struct sym_tcb *tp, int target, Tekram_nvram *nvram)
{
        struct Tekram_target *tn = &nvram->target[target];

        if (tn->flags & TEKRAM_TAGGED_COMMANDS) {
                tp->usrtags = 2 << nvram->max_tags_index;
        }

        if (tn->flags & TEKRAM_DISCONNECT_ENABLE)
                tp->usrflags |= SYM_DISC_ENABLED;
 
        if (tn->flags & TEKRAM_SYNC_NEGO)
                tp->usr_period = Tekram_sync[tn->sync_index & 0xf];
        tp->usr_width = (tn->flags & TEKRAM_WIDE_NEGO) ? 1 : 0;
}

/*
 *  Get target setup from NVRAM.
 */
void sym_nvram_setup_target(struct sym_tcb *tp, int target, struct sym_nvram *nvp)
{
        switch (nvp->type) {
        case SYM_SYMBIOS_NVRAM:
                sym_Symbios_setup_target(tp, target, &nvp->data.Symbios);
                break;
        case SYM_TEKRAM_NVRAM:
                sym_Tekram_setup_target(tp, target, &nvp->data.Tekram);
                break;
        default:
                break;
        }
}

#ifdef  SYM_CONF_DEBUG_NVRAM
/*
 *  Dump Symbios format NVRAM for debugging purpose.
 */
static void sym_display_Symbios_nvram(struct sym_device *np, Symbios_nvram *nvram)
{
        int i;

        /* display Symbios nvram host data */
        printf("%s: HOST ID=%d%s%s%s%s%s%s\n",
                sym_name(np), nvram->host_id & 0x0f,
                (nvram->flags  & SYMBIOS_SCAM_ENABLE)   ? " SCAM"       :"",
                (nvram->flags  & SYMBIOS_PARITY_ENABLE) ? " PARITY"     :"",
                (nvram->flags  & SYMBIOS_VERBOSE_MSGS)  ? " VERBOSE"    :"", 
                (nvram->flags  & SYMBIOS_CHS_MAPPING)   ? " CHS_ALT"    :"", 
                (nvram->flags2 & SYMBIOS_AVOID_BUS_RESET)?" NO_RESET"   :"",
                (nvram->flags1 & SYMBIOS_SCAN_HI_LO)    ? " HI_LO"      :"");

        /* display Symbios nvram drive data */
        for (i = 0 ; i < 15 ; i++) {
                struct Symbios_target *tn = &nvram->target[i];
                printf("%s-%d:%s%s%s%s WIDTH=%d SYNC=%d TMO=%d\n",
                sym_name(np), i,
                (tn->flags & SYMBIOS_DISCONNECT_ENABLE) ? " DISC"       : "",
                (tn->flags & SYMBIOS_SCAN_AT_BOOT_TIME) ? " SCAN_BOOT"  : "",
                (tn->flags & SYMBIOS_SCAN_LUNS)         ? " SCAN_LUNS"  : "",
                (tn->flags & SYMBIOS_QUEUE_TAGS_ENABLED)? " TCQ"        : "",
                tn->bus_width,
                tn->sync_period / 4,
                tn->timeout);
        }
}

/*
 *  Dump TEKRAM format NVRAM for debugging purpose.
 */
static void sym_display_Tekram_nvram(struct sym_device *np, Tekram_nvram *nvram)
{
        int i, tags, boot_delay;
        char *rem;

        /* display Tekram nvram host data */
        tags = 2 << nvram->max_tags_index;
        boot_delay = 0;
        if (nvram->boot_delay_index < 6)
                boot_delay = Tekram_boot_delay[nvram->boot_delay_index];
        switch ((nvram->flags & TEKRAM_REMOVABLE_FLAGS) >> 6) {
        default:
        case 0: rem = "";                       break;
        case 1: rem = " REMOVABLE=boot device"; break;
        case 2: rem = " REMOVABLE=all";         break;
        }

        printf("%s: HOST ID=%d%s%s%s%s%s%s%s%s%s BOOT DELAY=%d tags=%d\n",
                sym_name(np), nvram->host_id & 0x0f,
                (nvram->flags1 & SYMBIOS_SCAM_ENABLE)   ? " SCAM"       :"",
                (nvram->flags & TEKRAM_MORE_THAN_2_DRIVES) ? " >2DRIVES":"",
                (nvram->flags & TEKRAM_DRIVES_SUP_1GB)  ? " >1GB"       :"",
                (nvram->flags & TEKRAM_RESET_ON_POWER_ON) ? " RESET"    :"",
                (nvram->flags & TEKRAM_ACTIVE_NEGATION) ? " ACT_NEG"    :"",
                (nvram->flags & TEKRAM_IMMEDIATE_SEEK)  ? " IMM_SEEK"   :"",
                (nvram->flags & TEKRAM_SCAN_LUNS)       ? " SCAN_LUNS"  :"",
                (nvram->flags1 & TEKRAM_F2_F6_ENABLED)  ? " F2_F6"      :"",
                rem, boot_delay, tags);

        /* display Tekram nvram drive data */
        for (i = 0; i <= 15; i++) {
                int sync, j;
                struct Tekram_target *tn = &nvram->target[i];
                j = tn->sync_index & 0xf;
                sync = Tekram_sync[j];
                printf("%s-%d:%s%s%s%s%s%s PERIOD=%d\n",
                sym_name(np), i,
                (tn->flags & TEKRAM_PARITY_CHECK)       ? " PARITY"     : "",
                (tn->flags & TEKRAM_SYNC_NEGO)          ? " SYNC"       : "",
                (tn->flags & TEKRAM_DISCONNECT_ENABLE)  ? " DISC"       : "",
                (tn->flags & TEKRAM_START_CMD)          ? " START"      : "",
                (tn->flags & TEKRAM_TAGGED_COMMANDS)    ? " TCQ"        : "",
                (tn->flags & TEKRAM_WIDE_NEGO)          ? " WIDE"       : "",
                sync);
        }
}
#else
static void sym_display_Symbios_nvram(struct sym_device *np, Symbios_nvram *nvram) { (void)np; (void)nvram; }
static void sym_display_Tekram_nvram(struct sym_device *np, Tekram_nvram *nvram) { (void)np; (void)nvram; }
#endif  /* SYM_CONF_DEBUG_NVRAM */


/*
 *  24C16 EEPROM reading.
 *
 *  GPOI0 - data in/data out
 *  GPIO1 - clock
 *  Symbios NVRAM wiring now also used by Tekram.
 */

#define SET_BIT 0
#define CLR_BIT 1
#define SET_CLK 2
#define CLR_CLK 3

/*
 *  Set/clear data/clock bit in GPIO0
 */
static void S24C16_set_bit(struct sym_device *np, u_char write_bit, u_char *gpreg, 
                          int bit_mode)
{
        udelay(5);
        switch (bit_mode) {
        case SET_BIT:
                *gpreg |= write_bit;
                break;
        case CLR_BIT:
                *gpreg &= 0xfe;
                break;
        case SET_CLK:
                *gpreg |= 0x02;
                break;
        case CLR_CLK:
                *gpreg &= 0xfd;
                break;

        }
        OUTB(np, nc_gpreg, *gpreg);
        INB(np, nc_mbox1);
        udelay(5);
}

/*
 *  Send START condition to NVRAM to wake it up.
 */
static void S24C16_start(struct sym_device *np, u_char *gpreg)
{
        S24C16_set_bit(np, 1, gpreg, SET_BIT);
        S24C16_set_bit(np, 0, gpreg, SET_CLK);
        S24C16_set_bit(np, 0, gpreg, CLR_BIT);
        S24C16_set_bit(np, 0, gpreg, CLR_CLK);
}

/*
 *  Send STOP condition to NVRAM - puts NVRAM to sleep... ZZzzzz!!
 */
static void S24C16_stop(struct sym_device *np, u_char *gpreg)
{
        S24C16_set_bit(np, 0, gpreg, SET_CLK);
        S24C16_set_bit(np, 1, gpreg, SET_BIT);
}

/*
 *  Read or write a bit to the NVRAM,
 *  read if GPIO0 input else write if GPIO0 output
 */
static void S24C16_do_bit(struct sym_device *np, u_char *read_bit, u_char write_bit, 
                         u_char *gpreg)
{
        S24C16_set_bit(np, write_bit, gpreg, SET_BIT);
        S24C16_set_bit(np, 0, gpreg, SET_CLK);
        if (read_bit)
                *read_bit = INB(np, nc_gpreg);
        S24C16_set_bit(np, 0, gpreg, CLR_CLK);
        S24C16_set_bit(np, 0, gpreg, CLR_BIT);
}

/*
 *  Output an ACK to the NVRAM after reading,
 *  change GPIO0 to output and when done back to an input
 */
static void S24C16_write_ack(struct sym_device *np, u_char write_bit, u_char *gpreg, 
                            u_char *gpcntl)
{
        OUTB(np, nc_gpcntl, *gpcntl & 0xfe);
        S24C16_do_bit(np, NULL, write_bit, gpreg);
        OUTB(np, nc_gpcntl, *gpcntl);
}

/*
 *  Input an ACK from NVRAM after writing,
 *  change GPIO0 to input and when done back to an output
 */
static void S24C16_read_ack(struct sym_device *np, u_char *read_bit, u_char *gpreg, 
                           u_char *gpcntl)
{
        OUTB(np, nc_gpcntl, *gpcntl | 0x01);
        S24C16_do_bit(np, read_bit, 1, gpreg);
        OUTB(np, nc_gpcntl, *gpcntl);
}

/*
 *  WRITE a byte to the NVRAM and then get an ACK to see it was accepted OK,
 *  GPIO0 must already be set as an output
 */
static void S24C16_write_byte(struct sym_device *np, u_char *ack_data, u_char write_data, 
                             u_char *gpreg, u_char *gpcntl)
{
        int x;
        
        for (x = 0; x < 8; x++)
                S24C16_do_bit(np, NULL, (write_data >> (7 - x)) & 0x01, gpreg);
                
        S24C16_read_ack(np, ack_data, gpreg, gpcntl);
}

/*
 *  READ a byte from the NVRAM and then send an ACK to say we have got it,
 *  GPIO0 must already be set as an input
 */
static void S24C16_read_byte(struct sym_device *np, u_char *read_data, u_char ack_data, 
                            u_char *gpreg, u_char *gpcntl)
{
        int x;
        u_char read_bit;

        *read_data = 0;
        for (x = 0; x < 8; x++) {
                S24C16_do_bit(np, &read_bit, 1, gpreg);
                *read_data |= ((read_bit & 0x01) << (7 - x));
        }

        S24C16_write_ack(np, ack_data, gpreg, gpcntl);
}

#ifdef SYM_CONF_NVRAM_WRITE_SUPPORT
/*
 *  Write 'len' bytes starting at 'offset'.
 */
static int sym_write_S24C16_nvram(struct sym_device *np, int offset,
                u_char *data, int len)
{
        u_char  gpcntl, gpreg;
        u_char  old_gpcntl, old_gpreg;
        u_char  ack_data;
        int     x;

        /* save current state of GPCNTL and GPREG */
        old_gpreg       = INB(np, nc_gpreg);
        old_gpcntl      = INB(np, nc_gpcntl);
        gpcntl          = old_gpcntl & 0x1c;

        /* set up GPREG & GPCNTL to set GPIO0 and GPIO1 in to known state */
        OUTB(np, nc_gpreg,  old_gpreg);
        OUTB(np, nc_gpcntl, gpcntl);

        /* this is to set NVRAM into a known state with GPIO0/1 both low */
        gpreg = old_gpreg;
        S24C16_set_bit(np, 0, &gpreg, CLR_CLK);
        S24C16_set_bit(np, 0, &gpreg, CLR_BIT);
                
        /* now set NVRAM inactive with GPIO0/1 both high */
        S24C16_stop(np, &gpreg);

        /* NVRAM has to be written in segments of 16 bytes */
        for (x = 0; x < len ; x += 16) {
                do {
                        S24C16_start(np, &gpreg);
                        S24C16_write_byte(np, &ack_data,
                                          0xa0 | (((offset+x) >> 7) & 0x0e),
                                          &gpreg, &gpcntl);
                } while (ack_data & 0x01);

                S24C16_write_byte(np, &ack_data, (offset+x) & 0xff, 
                                  &gpreg, &gpcntl);

                for (y = 0; y < 16; y++)
                        S24C16_write_byte(np, &ack_data, data[x+y], 
                                          &gpreg, &gpcntl);
                S24C16_stop(np, &gpreg);
        }

        /* return GPIO0/1 to original states after having accessed NVRAM */
        OUTB(np, nc_gpcntl, old_gpcntl);
        OUTB(np, nc_gpreg,  old_gpreg);

        return 0;
}
#endif /* SYM_CONF_NVRAM_WRITE_SUPPORT */

/*
 *  Read 'len' bytes starting at 'offset'.
 */
static int sym_read_S24C16_nvram(struct sym_device *np, int offset, u_char *data, int len)
{
        u_char  gpcntl, gpreg;
        u_char  old_gpcntl, old_gpreg;
        u_char  ack_data;
        int     retv = 1;
        int     x;

        /* save current state of GPCNTL and GPREG */
        old_gpreg       = INB(np, nc_gpreg);
        old_gpcntl      = INB(np, nc_gpcntl);
        gpcntl          = old_gpcntl & 0x1c;

        /* set up GPREG & GPCNTL to set GPIO0 and GPIO1 in to known state */
        OUTB(np, nc_gpreg,  old_gpreg);
        OUTB(np, nc_gpcntl, gpcntl);

        /* this is to set NVRAM into a known state with GPIO0/1 both low */
        gpreg = old_gpreg;
        S24C16_set_bit(np, 0, &gpreg, CLR_CLK);
        S24C16_set_bit(np, 0, &gpreg, CLR_BIT);
                
        /* now set NVRAM inactive with GPIO0/1 both high */
        S24C16_stop(np, &gpreg);
        
        /* activate NVRAM */
        S24C16_start(np, &gpreg);

        /* write device code and random address MSB */
        S24C16_write_byte(np, &ack_data,
                0xa0 | ((offset >> 7) & 0x0e), &gpreg, &gpcntl);
        if (ack_data & 0x01)
                goto out;

        /* write random address LSB */
        S24C16_write_byte(np, &ack_data,
                offset & 0xff, &gpreg, &gpcntl);
        if (ack_data & 0x01)
                goto out;

        /* regenerate START state to set up for reading */
        S24C16_start(np, &gpreg);
        
        /* rewrite device code and address MSB with read bit set (lsb = 0x01) */
        S24C16_write_byte(np, &ack_data,
                0xa1 | ((offset >> 7) & 0x0e), &gpreg, &gpcntl);
        if (ack_data & 0x01)
                goto out;

        /* now set up GPIO0 for inputting data */
        gpcntl |= 0x01;
        OUTB(np, nc_gpcntl, gpcntl);
                
        /* input all requested data - only part of total NVRAM */
        for (x = 0; x < len; x++) 
                S24C16_read_byte(np, &data[x], (x == (len-1)), &gpreg, &gpcntl);

        /* finally put NVRAM back in inactive mode */
        gpcntl &= 0xfe;
        OUTB(np, nc_gpcntl, gpcntl);
        S24C16_stop(np, &gpreg);
        retv = 0;
out:
        /* return GPIO0/1 to original states after having accessed NVRAM */
        OUTB(np, nc_gpcntl, old_gpcntl);
        OUTB(np, nc_gpreg,  old_gpreg);

        return retv;
}

#undef SET_BIT
#undef CLR_BIT
#undef SET_CLK
#undef CLR_CLK

/*
 *  Try reading Symbios NVRAM.
 *  Return 0 if OK.
 */
static int sym_read_Symbios_nvram(struct sym_device *np, Symbios_nvram *nvram)
{
        static u_char Symbios_trailer[6] = {0xfe, 0xfe, 0, 0, 0, 0};
        u_char *data = (u_char *) nvram;
        int len  = sizeof(*nvram);
        u_short csum;
        int x;

        /* probe the 24c16 and read the SYMBIOS 24c16 area */
        if (sym_read_S24C16_nvram (np, SYMBIOS_NVRAM_ADDRESS, data, len))
                return 1;

        /* check valid NVRAM signature, verify byte count and checksum */
        if (nvram->type != 0 ||
            memcmp(nvram->trailer, Symbios_trailer, 6) ||
            nvram->byte_count != len - 12)
                return 1;

        /* verify checksum */
        for (x = 6, csum = 0; x < len - 6; x++)
                csum += data[x];
        if (csum != nvram->checksum)
                return 1;

        return 0;
}

/*
 *  93C46 EEPROM reading.
 *
 *  GPOI0 - data in
 *  GPIO1 - data out
 *  GPIO2 - clock
 *  GPIO4 - chip select
 *
 *  Used by Tekram.
 */

/*
 *  Pulse clock bit in GPIO0
 */
static void T93C46_Clk(struct sym_device *np, u_char *gpreg)
{
        OUTB(np, nc_gpreg, *gpreg | 0x04);
        INB(np, nc_mbox1);
        udelay(2);
        OUTB(np, nc_gpreg, *gpreg);
}

/* 
 *  Read bit from NVRAM
 */
static void T93C46_Read_Bit(struct sym_device *np, u_char *read_bit, u_char *gpreg)
{
        udelay(2);
        T93C46_Clk(np, gpreg);
        *read_bit = INB(np, nc_gpreg);
}

/*
 *  Write bit to GPIO0
 */
static void T93C46_Write_Bit(struct sym_device *np, u_char write_bit, u_char *gpreg)
{
        if (write_bit & 0x01)
                *gpreg |= 0x02;
        else
                *gpreg &= 0xfd;
                
        *gpreg |= 0x10;
                
        OUTB(np, nc_gpreg, *gpreg);
        INB(np, nc_mbox1);
        udelay(2);

        T93C46_Clk(np, gpreg);
}

/*
 *  Send STOP condition to NVRAM - puts NVRAM to sleep... ZZZzzz!!
 */
static void T93C46_Stop(struct sym_device *np, u_char *gpreg)
{
        *gpreg &= 0xef;
        OUTB(np, nc_gpreg, *gpreg);
        INB(np, nc_mbox1);
        udelay(2);

        T93C46_Clk(np, gpreg);
}

/*
 *  Send read command and address to NVRAM
 */
static void T93C46_Send_Command(struct sym_device *np, u_short write_data, 
                                u_char *read_bit, u_char *gpreg)
{
        int x;

        /* send 9 bits, start bit (1), command (2), address (6)  */
        for (x = 0; x < 9; x++)
                T93C46_Write_Bit(np, (u_char) (write_data >> (8 - x)), gpreg);

        *read_bit = INB(np, nc_gpreg);
}

/*
 *  READ 2 bytes from the NVRAM
 */
static void T93C46_Read_Word(struct sym_device *np,
                unsigned short *nvram_data, unsigned char *gpreg)
{
        int x;
        u_char read_bit;

        *nvram_data = 0;
        for (x = 0; x < 16; x++) {
                T93C46_Read_Bit(np, &read_bit, gpreg);

                if (read_bit & 0x01)
                        *nvram_data |=  (0x01 << (15 - x));
                else
                        *nvram_data &= ~(0x01 << (15 - x));
        }
}

/*
 *  Read Tekram NvRAM data.
 */
static int T93C46_Read_Data(struct sym_device *np, unsigned short *data,
                int len, unsigned char *gpreg)
{
        int x;

        for (x = 0; x < len; x++)  {
                unsigned char read_bit;
                /* output read command and address */
                T93C46_Send_Command(np, 0x180 | x, &read_bit, gpreg);
                if (read_bit & 0x01)
                        return 1; /* Bad */
                T93C46_Read_Word(np, &data[x], gpreg);
                T93C46_Stop(np, gpreg);
        }

        return 0;
}

/*
 *  Try reading 93C46 Tekram NVRAM.
 */
static int sym_read_T93C46_nvram(struct sym_device *np, Tekram_nvram *nvram)
{
        u_char gpcntl, gpreg;
        u_char old_gpcntl, old_gpreg;
        int retv = 1;

        /* save current state of GPCNTL and GPREG */
        old_gpreg       = INB(np, nc_gpreg);
        old_gpcntl      = INB(np, nc_gpcntl);

        /* set up GPREG & GPCNTL to set GPIO0/1/2/4 in to known state, 0 in,
           1/2/4 out */
        gpreg = old_gpreg & 0xe9;
        OUTB(np, nc_gpreg, gpreg);
        gpcntl = (old_gpcntl & 0xe9) | 0x09;
        OUTB(np, nc_gpcntl, gpcntl);

        /* input all of NVRAM, 64 words */
        retv = T93C46_Read_Data(np, (u_short *) nvram,
                                sizeof(*nvram) / sizeof(short), &gpreg);
        
        /* return GPIO0/1/2/4 to original states after having accessed NVRAM */
        OUTB(np, nc_gpcntl, old_gpcntl);
        OUTB(np, nc_gpreg,  old_gpreg);

        return retv;
}

/*
 *  Try reading Tekram NVRAM.
 *  Return 0 if OK.
 */
static int sym_read_Tekram_nvram (struct sym_device *np, Tekram_nvram *nvram)
{
        u_char *data = (u_char *) nvram;
        int len = sizeof(*nvram);
        u_short csum;
        int x;

        switch (np->pdev->device) {
        case PCI_DEVICE_ID_NCR_53C885:
        case PCI_DEVICE_ID_NCR_53C895:
        case PCI_DEVICE_ID_NCR_53C896:
                x = sym_read_S24C16_nvram(np, TEKRAM_24C16_NVRAM_ADDRESS,
                                          data, len);
                break;
        case PCI_DEVICE_ID_NCR_53C875:
                x = sym_read_S24C16_nvram(np, TEKRAM_24C16_NVRAM_ADDRESS,
                                          data, len);
                if (!x)
                        break;
        default:
                x = sym_read_T93C46_nvram(np, nvram);
                break;
        }
        if (x)
                return 1;

        /* verify checksum */
        for (x = 0, csum = 0; x < len - 1; x += 2)
                csum += data[x] + (data[x+1] << 8);
        if (csum != 0x1234)
                return 1;

        return 0;
}

#ifdef CONFIG_PARISC
/*
 * Host firmware (PDC) keeps a table for altering SCSI capabilities.
 * Many newer machines export one channel of 53c896 chip as SE, 50-pin HD.
 * Also used for Multi-initiator SCSI clusters to set the SCSI Initiator ID.
 */
static int sym_read_parisc_pdc(struct sym_device *np, struct pdc_initiator *pdc)
{
        struct hardware_path hwpath;
        get_pci_node_path(np->pdev, &hwpath);
        if (!pdc_get_initiator(&hwpath, pdc))
                return 0;

        return SYM_PARISC_PDC;
}
#else
static inline int sym_read_parisc_pdc(struct sym_device *np,
                                        struct pdc_initiator *x)
{
        return 0;
}
#endif

/*
 *  Try reading Symbios or Tekram NVRAM
 */
int sym_read_nvram(struct sym_device *np, struct sym_nvram *nvp)
{
        if (!sym_read_Symbios_nvram(np, &nvp->data.Symbios)) {
                nvp->type = SYM_SYMBIOS_NVRAM;
                sym_display_Symbios_nvram(np, &nvp->data.Symbios);
        } else if (!sym_read_Tekram_nvram(np, &nvp->data.Tekram)) {
                nvp->type = SYM_TEKRAM_NVRAM;
                sym_display_Tekram_nvram(np, &nvp->data.Tekram);
        } else {
                nvp->type = sym_read_parisc_pdc(np, &nvp->data.parisc);
        }
        return nvp->type;
}

char *sym_nvram_type(struct sym_nvram *nvp)
{
        switch (nvp->type) {
        case SYM_SYMBIOS_NVRAM:
                return "Symbios NVRAM";
        case SYM_TEKRAM_NVRAM:
                return "Tekram NVRAM";
        case SYM_PARISC_PDC:
                return "PA-RISC Firmware";
        default:
                return "No NVRAM";
        }
}