// SPDX-License-Identifier: GPL-2.0
/*
 * ip22-nvram.c: NVRAM and serial EEPROM handling.
 *
 * Copyright (C) 2003 Ladislav Michl (ladis@linux-mips.org)
 */
#include <linux/export.h>

#include <asm/sgi/hpc3.h>
#include <asm/sgi/ip22.h>

/* Control opcode for serial eeprom  */
#define EEPROM_READ     0xc000  /* serial memory read */
#define EEPROM_WEN      0x9800  /* write enable before prog modes */
#define EEPROM_WRITE    0xa000  /* serial memory write */
#define EEPROM_WRALL    0x8800  /* write all registers */
#define EEPROM_WDS      0x8000  /* disable all programming */
#define EEPROM_PRREAD   0xc000  /* read protect register */
#define EEPROM_PREN     0x9800  /* enable protect register mode */
#define EEPROM_PRCLEAR  0xffff  /* clear protect register */
#define EEPROM_PRWRITE  0xa000  /* write protect register */
#define EEPROM_PRDS     0x8000  /* disable protect register, forever */

#define EEPROM_EPROT    0x01    /* Protect register enable */
#define EEPROM_CSEL     0x02    /* Chip select */
#define EEPROM_ECLK     0x04    /* EEPROM clock */
#define EEPROM_DATO     0x08    /* Data out */
#define EEPROM_DATI     0x10    /* Data in */

/* We need to use these functions early... */
#define delay() ({                                              \
        int x;                                                  \
        for (x=0; x<100000; x++) __asm__ __volatile__(""); })

#define eeprom_cs_on(ptr) ({    \
        __raw_writel(__raw_readl(ptr) & ~EEPROM_DATO, ptr);     \
        __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr);     \
        __raw_writel(__raw_readl(ptr) & ~EEPROM_EPROT, ptr);    \
        delay();                                                \
        __raw_writel(__raw_readl(ptr) | EEPROM_CSEL, ptr);      \
        __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })


#define eeprom_cs_off(ptr) ({   \
        __raw_writel(__raw_readl(ptr) & ~EEPROM_ECLK, ptr);     \
        __raw_writel(__raw_readl(ptr) & ~EEPROM_CSEL, ptr);     \
        __raw_writel(__raw_readl(ptr) | EEPROM_EPROT, ptr);     \
        __raw_writel(__raw_readl(ptr) | EEPROM_ECLK, ptr); })

#define BITS_IN_COMMAND 11
/*
 * clock in the nvram command and the register number. For the
 * national semiconductor nv ram chip the op code is 3 bits and
 * the address is 6/8 bits.
 */
static inline void eeprom_cmd(unsigned int *ctrl, unsigned cmd, unsigned reg)
{
        unsigned short ser_cmd;
        int i;

        ser_cmd = cmd | (reg << (16 - BITS_IN_COMMAND));
        for (i = 0; i < BITS_IN_COMMAND; i++) {
                if (ser_cmd & (1<<15))  /* if high order bit set */
                        __raw_writel(__raw_readl(ctrl) | EEPROM_DATO, ctrl);
                else
                        __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
                __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
                delay();
                __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
                delay();
                ser_cmd <<= 1;
        }
        /* see data sheet timing diagram */
        __raw_writel(__raw_readl(ctrl) & ~EEPROM_DATO, ctrl);
}

unsigned short ip22_eeprom_read(unsigned int *ctrl, int reg)
{
        unsigned short res = 0;
        int i;

        __raw_writel(__raw_readl(ctrl) & ~EEPROM_EPROT, ctrl);
        eeprom_cs_on(ctrl);
        eeprom_cmd(ctrl, EEPROM_READ, reg);

        /* clock the data ouf of serial mem */
        for (i = 0; i < 16; i++) {
                __raw_writel(__raw_readl(ctrl) & ~EEPROM_ECLK, ctrl);
                delay();
                __raw_writel(__raw_readl(ctrl) | EEPROM_ECLK, ctrl);
                delay();
                res <<= 1;
                if (__raw_readl(ctrl) & EEPROM_DATI)
                        res |= 1;
        }

        eeprom_cs_off(ctrl);

        return res;
}

EXPORT_SYMBOL(ip22_eeprom_read);

/*
 * Read specified register from main NVRAM
 */
unsigned short ip22_nvram_read(int reg)
{
        if (ip22_is_fullhouse())
                /* IP22 (Indigo2 aka FullHouse) stores env variables into
                 * 93CS56 Microwire Bus EEPROM 2048 Bit (128x16) */
                return ip22_eeprom_read(&hpc3c0->eeprom, reg);
        else {
                unsigned short tmp;
                /* IP24 (Indy aka Guiness) uses DS1386 8K version */
                reg <<= 1;
                tmp = hpc3c0->bbram[reg++] & 0xff;
                return (tmp << 8) | (hpc3c0->bbram[reg] & 0xff);
        }
}

EXPORT_SYMBOL(ip22_nvram_read);