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 */
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
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 */
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
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