xref: /openbmc/linux/arch/mips/sgi-ip22/ip22-nvram.c (revision b2441318)
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  */
eeprom_cmd(unsigned int * ctrl,unsigned cmd,unsigned reg)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 
ip22_eeprom_read(unsigned int * ctrl,int reg)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  */
ip22_nvram_read(int reg)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);
123