1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * c 2001 PPC 64 Team, IBM Corp
4 *
5 * /dev/nvram driver for PPC
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/spinlock.h>
12 #include <linux/uaccess.h>
13 #include <asm/prom.h>
14 #include <asm/machdep.h>
15 #include <asm/rtas.h>
16 #include "chrp.h"
17
18 static unsigned int nvram_size;
19 static unsigned char nvram_buf[4];
20 static DEFINE_SPINLOCK(nvram_lock);
21
chrp_nvram_read_val(int addr)22 static unsigned char chrp_nvram_read_val(int addr)
23 {
24 unsigned int done;
25 unsigned long flags;
26 unsigned char ret;
27
28 if (addr >= nvram_size) {
29 printk(KERN_DEBUG "%s: read addr %d > nvram_size %u\n",
30 current->comm, addr, nvram_size);
31 return 0xff;
32 }
33 spin_lock_irqsave(&nvram_lock, flags);
34 if ((rtas_call(rtas_token("nvram-fetch"), 3, 2, &done, addr,
35 __pa(nvram_buf), 1) != 0) || 1 != done)
36 ret = 0xff;
37 else
38 ret = nvram_buf[0];
39 spin_unlock_irqrestore(&nvram_lock, flags);
40
41 return ret;
42 }
43
chrp_nvram_write_val(int addr,unsigned char val)44 static void chrp_nvram_write_val(int addr, unsigned char val)
45 {
46 unsigned int done;
47 unsigned long flags;
48
49 if (addr >= nvram_size) {
50 printk(KERN_DEBUG "%s: write addr %d > nvram_size %u\n",
51 current->comm, addr, nvram_size);
52 return;
53 }
54 spin_lock_irqsave(&nvram_lock, flags);
55 nvram_buf[0] = val;
56 if ((rtas_call(rtas_token("nvram-store"), 3, 2, &done, addr,
57 __pa(nvram_buf), 1) != 0) || 1 != done)
58 printk(KERN_DEBUG "rtas IO error storing 0x%02x at %d", val, addr);
59 spin_unlock_irqrestore(&nvram_lock, flags);
60 }
61
chrp_nvram_size(void)62 static ssize_t chrp_nvram_size(void)
63 {
64 return nvram_size;
65 }
66
chrp_nvram_init(void)67 void __init chrp_nvram_init(void)
68 {
69 struct device_node *nvram;
70 const __be32 *nbytes_p;
71 unsigned int proplen;
72
73 nvram = of_find_node_by_type(NULL, "nvram");
74 if (nvram == NULL)
75 return;
76
77 nbytes_p = of_get_property(nvram, "#bytes", &proplen);
78 if (nbytes_p == NULL || proplen != sizeof(unsigned int)) {
79 of_node_put(nvram);
80 return;
81 }
82
83 nvram_size = be32_to_cpup(nbytes_p);
84
85 printk(KERN_INFO "CHRP nvram contains %u bytes\n", nvram_size);
86 of_node_put(nvram);
87
88 ppc_md.nvram_read_val = chrp_nvram_read_val;
89 ppc_md.nvram_write_val = chrp_nvram_write_val;
90 ppc_md.nvram_size = chrp_nvram_size;
91
92 return;
93 }
94
95 MODULE_LICENSE("GPL v2");
96