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 <linux/of.h>
14#include <asm/machdep.h>
15#include <asm/rtas.h>
16#include "chrp.h"
17
18static unsigned int nvram_size;
19static unsigned char nvram_buf[4];
20static DEFINE_SPINLOCK(nvram_lock);
21
22static 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_function_token(RTAS_FN_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
44static 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_function_token(RTAS_FN_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
62static ssize_t chrp_nvram_size(void)
63{
64	return nvram_size;
65}
66
67void __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
95MODULE_LICENSE("GPL v2");
96