mips/sgi-ip22/ip22-nvram.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * ip22-nvram.c: NVRAM and serial EEPROM handling.
0004  *
0005  * Copyright (C) 2003 Ladislav Michl (ladis@linux-mips.org)
0006  */
0007 #include <linux/export.h>
0008
0009 #include <asm/sgi/hpc3.h>
0010 #include <asm/sgi/ip22.h>
0011
0012 /* Control opcode for serial eeprom  */
0013 #define EEPROM_READ 0xc000  /* serial memory read */
0014 #define EEPROM_WEN  0x9800  /* write enable before prog modes */
0015 #define EEPROM_WRITE    0xa000  /* serial memory write */
0016 #define EEPROM_WRALL    0x8800  /* write all registers */
0017 #define EEPROM_WDS  0x8000  /* disable all programming */
0018 #define EEPROM_PRREAD   0xc000  /* read protect register */
0019 #define EEPROM_PREN 0x9800  /* enable protect register mode */
0020 #define EEPROM_PRCLEAR  0xffff  /* clear protect register */
0021 #define EEPROM_PRWRITE  0xa000  /* write protect register */
0022 #define EEPROM_PRDS 0x8000  /* disable protect register, forever */
0023
0024 #define EEPROM_EPROT    0x01    /* Protect register enable */
0025 #define EEPROM_CSEL 0x02    /* Chip select */
0026 #define EEPROM_ECLK 0x04    /* EEPROM clock */
0027 #define EEPROM_DATO 0x08    /* Data out */
0028 #define EEPROM_DATI 0x10    /* Data in */
0029
0030 /* We need to use these functions early... */
0031 #define delay() ({                      \
0032     int x;                          \
0033     for (x=0; x<100000; x++) __asm__ __volatile__(""); })
0034
0035 #define eeprom_cs_on(ptr) ({    \
0036     __raw_writel(__raw_readl(ptr) & ~EEPROM_DATO, ptr); \
0037     __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr); \
0038     __raw_writel(__raw_readl(ptr) & ~EEPROM_EPROT, ptr);    \
0039     delay();                        \
0040     __raw_writel(__raw_readl(ptr) | EEPROM_CSEL, ptr);  \
0041     __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })
0042
0043
0044 #define eeprom_cs_off(ptr) ({   \
0045     __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr); \
0046     __raw_writel(__raw_readl(ptr) & ~EEPROM_CSEL, ptr); \
0047     __raw_writel(__raw_readl(ptr) | EEPROM_EPROT, ptr); \
0048     __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })
0049
0050 #define BITS_IN_COMMAND 11
0051 /*
0052  * clock in the nvram command and the register number. For the
0053  * national semiconductor nv ram chip the op code is 3 bits and
0054  * the address is 6/8 bits.
0055  */
0056 static inline void eeprom_cmd(unsigned int *ctrl, unsigned cmd, unsigned reg)
0057 {
0058     unsigned short ser_cmd;
0059     int i;
0060
0061     ser_cmd = cmd | (reg << (16 - BITS_IN_COMMAND));
0062     for (i = 0; i < BITS_IN_COMMAND; i++) {
0063         if (ser_cmd & (1<<15))  /* if high order bit set */
0064             __raw_writel(__raw_readl(ctrl) | EEPROM_DATO, ctrl);
0065         else
0066             __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
0067         __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
0068         delay();
0069         __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
0070         delay();
0071         ser_cmd <<= 1;
0072     }
0073     /* see data sheet timing diagram */
0074     __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
0075 }
0076
0077 unsigned short ip22_eeprom_read(unsigned int *ctrl, int reg)
0078 {
0079     unsigned short res = 0;
0080     int i;
0081
0082     __raw_writel(__raw_readl(ctrl) & ~EEPROM_EPROT, ctrl);
0083     eeprom_cs_on(ctrl);
0084     eeprom_cmd(ctrl, EEPROM_READ, reg);
0085
0086     /* clock the data ouf of serial mem */
0087     for (i = 0; i < 16; i++) {
0088         __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
0089         delay();
0090         __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
0091         delay();
0092         res <<= 1;
0093         if (__raw_readl(ctrl) & EEPROM_DATI)
0094             res |= 1;
0095     }
0096
0097     eeprom_cs_off(ctrl);
0098
0099     return res;
0100 }
0101
0102 EXPORT_SYMBOL(ip22_eeprom_read);
0103
0104 /*
0105  * Read specified register from main NVRAM
0106  */
0107 unsigned short ip22_nvram_read(int reg)
0108 {
0109     if (ip22_is_fullhouse())
0110         /* IP22 (Indigo2 aka FullHouse) stores env variables into
0111          * 93CS56 Microwire Bus EEPROM 2048 Bit (128x16) */
0112         return ip22_eeprom_read(&hpc3c0->eeprom, reg);
0113     else {
0114         unsigned short tmp;
0115         /* IP24 (Indy aka Guiness) uses DS1386 8K version */
0116         reg <<= 1;
0117         tmp = hpc3c0->bbram[reg++] & 0xff;
0118         return (tmp << 8) | (hpc3c0->bbram[reg] & 0xff);
0119     }
0120 }
0121
0122 EXPORT_SYMBOL(ip22_nvram_read);