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 */
55static inline void eeprom_cmd(unsigned int *ctrl, unsigned cmd, unsigned reg)
56{
57	unsigned short ser_cmd;
58	int i;
59
60	ser_cmd = cmd | (reg << (16 - BITS_IN_COMMAND));
61	for (i = 0; i < BITS_IN_COMMAND; i++) {
62		if (ser_cmd & (1<<15))	/* if high order bit set */
63			writel(readl(ctrl) | EEPROM_DATO, ctrl);
64		else
65			writel(readl(ctrl) & ~EEPROM_DATO, ctrl);
66		writel(readl(ctrl) & ~EEPROM_ECLK, ctrl);
67		writel(readl(ctrl) | EEPROM_ECLK, ctrl);
68		ser_cmd <<= 1;
69	}
70	/* see data sheet timing diagram */
71	writel(readl(ctrl) & ~EEPROM_DATO, ctrl);
72}
73
74unsigned short ip22_eeprom_read(unsigned int *ctrl, int reg)
75{
76	unsigned short res = 0;
77	int i;
78
79	writel(readl(ctrl) & ~EEPROM_EPROT, ctrl);
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		writel(readl(ctrl) & ~EEPROM_ECLK, ctrl);
86		delay();
87		writel(readl(ctrl) | EEPROM_ECLK, ctrl);
88		delay();
89		res <<= 1;
90		if (readl(ctrl) & EEPROM_DATI)
91			res |= 1;
92	}
93
94	eeprom_cs_off(ctrl);
95
96	return res;
97}
98
99EXPORT_SYMBOL(ip22_eeprom_read);
100
101/*
102 * Read specified register from main NVRAM
103 */
104unsigned 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
119EXPORT_SYMBOL(ip22_nvram_read);
120