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

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * ip22-nvram.c: NVRAM and serial EEPROM handling.
   4  *
   5  * Copyright (C) 2003 Ladislav Michl (ladis@linux-mips.org)
   6  */
   7 #include <linux/export.h>
   8
   9 #include <asm/sgi/hpc3.h>
  10 #include <asm/sgi/ip22.h>
  11
  12 /* Control opcode for serial eeprom  */
  13 #define EEPROM_READ     0xc000  /* serial memory read */
  14 #define EEPROM_WEN      0x9800  /* write enable before prog modes */
  15 #define EEPROM_WRITE    0xa000  /* serial memory write */
  16 #define EEPROM_WRALL    0x8800  /* write all registers */
  17 #define EEPROM_WDS      0x8000  /* disable all programming */
  18 #define EEPROM_PRREAD   0xc000  /* read protect register */
  19 #define EEPROM_PREN     0x9800  /* enable protect register mode */
  20 #define EEPROM_PRCLEAR  0xffff  /* clear protect register */
  21 #define EEPROM_PRWRITE  0xa000  /* write protect register */
  22 #define EEPROM_PRDS     0x8000  /* disable protect register, forever */
  23
  24 #define EEPROM_EPROT    0x01    /* Protect register enable */
  25 #define EEPROM_CSEL     0x02    /* Chip select */
  26 #define EEPROM_ECLK     0x04    /* EEPROM clock */
  27 #define EEPROM_DATO     0x08    /* Data out */
  28 #define EEPROM_DATI     0x10    /* Data in */
  29
  30 /* We need to use these functions early... */
  31 #define delay() ({                                              \
  32         int x;                                                  \
  33         for (x=0; x<100000; x++) __asm__ __volatile__(""); })
  34
  35 #define eeprom_cs_on(ptr) ({    \
  36         __raw_writel(__raw_readl(ptr) & ~EEPROM_DATO, ptr);     \
  37         __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr);     \
  38         __raw_writel(__raw_readl(ptr) & ~EEPROM_EPROT, ptr);    \
  39         delay();                                                \
  40         __raw_writel(__raw_readl(ptr) | EEPROM_CSEL, ptr);      \
  41         __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })
  42
  43
  44 #define eeprom_cs_off(ptr) ({   \
  45         __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr);     \
  46         __raw_writel(__raw_readl(ptr) & ~EEPROM_CSEL, ptr);     \
  47         __raw_writel(__raw_readl(ptr) | EEPROM_EPROT, ptr);     \
  48         __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })
  49
  50 #define BITS_IN_COMMAND 11
  51 /*
  52  * clock in the nvram command and the register number. For the
  53  * national semiconductor nv ram chip the op code is 3 bits and
  54  * the address is 6/8 bits.
  55  */
  56 static inline void eeprom_cmd(unsigned int *ctrl, unsigned cmd, 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                         __raw_writel(__raw_readl(ctrl) | EEPROM_DATO, ctrl);
  65                 else
  66                         __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
  67                 __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
  68                 delay();
  69                 __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
  70                 delay();
  71                 ser_cmd <<= 1;
  72         }
  73         /* see data sheet timing diagram */
  74         __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
  75 }
  76
  77 unsigned short ip22_eeprom_read(unsigned int *ctrl, int reg)
  78 {
  79         unsigned short res = 0;
  80         int i;
  81
  82         __raw_writel(__raw_readl(ctrl) & ~EEPROM_EPROT, ctrl);
  83         eeprom_cs_on(ctrl);
  84         eeprom_cmd(ctrl, EEPROM_READ, reg);
  85
  86         /* clock the data ouf of serial mem */
  87         for (i = 0; i < 16; i++) {
  88                 __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
  89                 delay();
  90                 __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
  91                 delay();
  92                 res <<= 1;
  93                 if (__raw_readl(ctrl) & EEPROM_DATI)
  94                         res |= 1;
  95         }
  96
  97         eeprom_cs_off(ctrl);
  98
  99         return res;
 100 }
 101
 102 EXPORT_SYMBOL(ip22_eeprom_read);
 103
 104 /*
 105  * Read specified register from main NVRAM
 106  */
 107 unsigned short ip22_nvram_read(int reg)
 108 {
 109         if (ip22_is_fullhouse())
 110                 /* IP22 (Indigo2 aka FullHouse) stores env variables into
 111                  * 93CS56 Microwire Bus EEPROM 2048 Bit (128x16) */
 112                 return ip22_eeprom_read(&hpc3c0->eeprom, reg);
 113         else {
 114                 unsigned short tmp;
 115                 /* IP24 (Indy aka Guiness) uses DS1386 8K version */
 116                 reg <<= 1;
 117                 tmp = hpc3c0->bbram[reg++] & 0xff;
 118                 return (tmp << 8) | (hpc3c0->bbram[reg] & 0xff);
 119         }
 120 }
 121
 122 EXPORT_SYMBOL(ip22_nvram_read);