arch/mips/sgi-ip22/ip22-nvram.c

   1 /*
   2  * ip22-nvram.c: NVRAM and serial EEPROM handling.
   3  *
   4  * Copyright (C) 2003 Ladislav Michl (ladis@linux-mips.org)
   5  */
   6 #include <linux/module.h>
   7
   8 #include <asm/sgi/hpc3.h>
   9 #include <asm/sgi/ip22.h>
  10
  11 /* Control opcode for serial eeprom  */
  12 #define EEPROM_READ     0xc000  /* serial memory read */
  13 #define EEPROM_WEN      0x9800  /* write enable before prog modes */
  14 #define EEPROM_WRITE    0xa000  /* serial memory write */
  15 #define EEPROM_WRALL    0x8800  /* write all registers */
  16 #define EEPROM_WDS      0x8000  /* disable all programming */
  17 #define EEPROM_PRREAD   0xc000  /* read protect register */
  18 #define EEPROM_PREN     0x9800  /* enable protect register mode */
  19 #define EEPROM_PRCLEAR  0xffff  /* clear protect register */
  20 #define EEPROM_PRWRITE  0xa000  /* write protect register */
  21 #define EEPROM_PRDS     0x8000  /* disable protect register, forever */
  22
  23 #define EEPROM_EPROT    0x01    /* Protect register enable */
  24 #define EEPROM_CSEL     0x02    /* Chip select */
  25 #define EEPROM_ECLK     0x04    /* EEPROM clock */
  26 #define EEPROM_DATO     0x08    /* Data out */
  27 #define EEPROM_DATI     0x10    /* Data in */
  28
  29 /* We need to use these functions early... */
  30 #define delay() ({                                              \
  31         int x;                                                  \
  32         for (x=0; x<100000; x++) __asm__ __volatile__(""); })
  33
  34 #define eeprom_cs_on(ptr) ({    \
  35         *ptr &= ~EEPROM_DATO;   \
  36         *ptr &= ~EEPROM_ECLK;   \
  37         *ptr &= ~EEPROM_EPROT;  \
  38         delay();                \
  39         *ptr |= EEPROM_CSEL;    \
  40         *ptr |= EEPROM_ECLK; })
  41
  42
  43 #define eeprom_cs_off(ptr) ({   \
  44         *ptr &= ~EEPROM_ECLK;   \
  45         *ptr &= ~EEPROM_CSEL;   \
  46         *ptr |= EEPROM_EPROT;   \
  47         *ptr |= EEPROM_ECLK; })
  48
  49 #define BITS_IN_COMMAND 11
  50 /*
  51  * clock in the nvram command and the register number. For the
  52  * national semiconductor nv ram chip the op code is 3 bits and
  53  * the address is 6/8 bits.
  54  */
  55 static inline void eeprom_cmd(volatile unsigned int *ctrl, unsigned cmd,
  56                               unsigned reg)
  57 {
  58         unsigned short ser_cmd;
  59         int i;
  60
  61         ser_cmd = cmd | (reg << (16 - BITS_IN_COMMAND));
  62         for (i = 0; i < BITS_IN_COMMAND; i++) {
  63                 if (ser_cmd & (1<<15))  /* if high order bit set */
  64                         *ctrl |= EEPROM_DATO;
  65                 else
  66                         *ctrl &= ~EEPROM_DATO;
  67                 *ctrl &= ~EEPROM_ECLK;
  68                 *ctrl |= EEPROM_ECLK;
  69                 ser_cmd <<= 1;
  70         }
  71         *ctrl &= ~EEPROM_DATO;  /* see data sheet timing diagram */
  72 }
  73
  74 unsigned short ip22_eeprom_read(volatile unsigned int *ctrl, int reg)
  75 {
  76         unsigned short res = 0;
  77         int i;
  78
  79         *ctrl &= ~EEPROM_EPROT;
  80         eeprom_cs_on(ctrl);
  81         eeprom_cmd(ctrl, EEPROM_READ, reg);
  82
  83         /* clock the data ouf of serial mem */
  84         for (i = 0; i < 16; i++) {
  85                 *ctrl &= ~EEPROM_ECLK;
  86                 delay();
  87                 *ctrl |= EEPROM_ECLK;
  88                 delay();
  89                 res <<= 1;
  90                 if (*ctrl & EEPROM_DATI)
  91                         res |= 1;
  92         }
  93
  94         eeprom_cs_off(ctrl);
  95
  96         return res;
  97 }
  98
  99 EXPORT_SYMBOL(ip22_eeprom_read);
 100
 101 /*
 102  * Read specified register from main NVRAM
 103  */
 104 unsigned short ip22_nvram_read(int reg)
 105 {
 106         if (ip22_is_fullhouse())
 107                 /* IP22 (Indigo2 aka FullHouse) stores env variables into
 108                  * 93CS56 Microwire Bus EEPROM 2048 Bit (128x16) */
 109                 return ip22_eeprom_read(&hpc3c0->eeprom, reg);
 110         else {
 111                 unsigned short tmp;
 112                 /* IP24 (Indy aka Guiness) uses DS1386 8K version */
 113                 reg <<= 1;
 114                 tmp = hpc3c0->bbram[reg++] & 0xff;
 115                 return (tmp << 8) | (hpc3c0->bbram[reg] & 0xff);
 116         }
 117 }
 118
 119 EXPORT_SYMBOL(ip22_nvram_read);