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 */
56static 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
77unsigned 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
102EXPORT_SYMBOL(ip22_eeprom_read);
103
104/*
105 * Read specified register from main NVRAM
106 */
107unsigned 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
122EXPORT_SYMBOL(ip22_nvram_read);
123