1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * CMOS/NV-RAM driver for Atari. Adapted from drivers/char/nvram.c.
4 * Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
5 * idea by and with help from Richard Jelinek <rj@suse.de>
6 * Portions copyright (c) 2001,2002 Sun Microsystems (thockin@sun.com)
7 * Further contributions from Cesar Barros, Erik Gilling, Tim Hockin and
8 * Wim Van Sebroeck.
9 */
10
11#include <linux/errno.h>
12#include <linux/init.h>
13#include <linux/mc146818rtc.h>
14#include <linux/module.h>
15#include <linux/nvram.h>
16#include <linux/proc_fs.h>
17#include <linux/seq_file.h>
18#include <linux/spinlock.h>
19#include <linux/types.h>
20#include <asm/atarihw.h>
21#include <asm/atariints.h>
22
23#define NVRAM_BYTES		50
24
25/* It is worth noting that these functions all access bytes of general
26 * purpose memory in the NVRAM - that is to say, they all add the
27 * NVRAM_FIRST_BYTE offset. Pass them offsets into NVRAM as if you did not
28 * know about the RTC cruft.
29 */
30
31/* Note that *all* calls to CMOS_READ and CMOS_WRITE must be done with
32 * rtc_lock held. Due to the index-port/data-port design of the RTC, we
33 * don't want two different things trying to get to it at once. (e.g. the
34 * periodic 11 min sync from kernel/time/ntp.c vs. this driver.)
35 */
36
37static unsigned char __nvram_read_byte(int i)
38{
39	return CMOS_READ(NVRAM_FIRST_BYTE + i);
40}
41
42/* This races nicely with trying to read with checksum checking */
43static void __nvram_write_byte(unsigned char c, int i)
44{
45	CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
46}
47
48/* On Ataris, the checksum is over all bytes except the checksum bytes
49 * themselves; these are at the very end.
50 */
51#define ATARI_CKS_RANGE_START	0
52#define ATARI_CKS_RANGE_END	47
53#define ATARI_CKS_LOC		48
54
55static int __nvram_check_checksum(void)
56{
57	int i;
58	unsigned char sum = 0;
59
60	for (i = ATARI_CKS_RANGE_START; i <= ATARI_CKS_RANGE_END; ++i)
61		sum += __nvram_read_byte(i);
62	return (__nvram_read_byte(ATARI_CKS_LOC) == (~sum & 0xff)) &&
63	       (__nvram_read_byte(ATARI_CKS_LOC + 1) == (sum & 0xff));
64}
65
66static void __nvram_set_checksum(void)
67{
68	int i;
69	unsigned char sum = 0;
70
71	for (i = ATARI_CKS_RANGE_START; i <= ATARI_CKS_RANGE_END; ++i)
72		sum += __nvram_read_byte(i);
73	__nvram_write_byte(~sum, ATARI_CKS_LOC);
74	__nvram_write_byte(sum, ATARI_CKS_LOC + 1);
75}
76
77long atari_nvram_set_checksum(void)
78{
79	spin_lock_irq(&rtc_lock);
80	__nvram_set_checksum();
81	spin_unlock_irq(&rtc_lock);
82	return 0;
83}
84
85long atari_nvram_initialize(void)
86{
87	loff_t i;
88
89	spin_lock_irq(&rtc_lock);
90	for (i = 0; i < NVRAM_BYTES; ++i)
91		__nvram_write_byte(0, i);
92	__nvram_set_checksum();
93	spin_unlock_irq(&rtc_lock);
94	return 0;
95}
96
97ssize_t atari_nvram_read(char *buf, size_t count, loff_t *ppos)
98{
99	char *p = buf;
100	loff_t i;
101
102	spin_lock_irq(&rtc_lock);
103	if (!__nvram_check_checksum()) {
104		spin_unlock_irq(&rtc_lock);
105		return -EIO;
106	}
107	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
108		*p = __nvram_read_byte(i);
109	spin_unlock_irq(&rtc_lock);
110
111	*ppos = i;
112	return p - buf;
113}
114
115ssize_t atari_nvram_write(char *buf, size_t count, loff_t *ppos)
116{
117	char *p = buf;
118	loff_t i;
119
120	spin_lock_irq(&rtc_lock);
121	if (!__nvram_check_checksum()) {
122		spin_unlock_irq(&rtc_lock);
123		return -EIO;
124	}
125	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
126		__nvram_write_byte(*p, i);
127	__nvram_set_checksum();
128	spin_unlock_irq(&rtc_lock);
129
130	*ppos = i;
131	return p - buf;
132}
133
134ssize_t atari_nvram_get_size(void)
135{
136	return NVRAM_BYTES;
137}
138
139#ifdef CONFIG_PROC_FS
140static struct {
141	unsigned char val;
142	const char *name;
143} boot_prefs[] = {
144	{ 0x80, "TOS" },
145	{ 0x40, "ASV" },
146	{ 0x20, "NetBSD (?)" },
147	{ 0x10, "Linux" },
148	{ 0x00, "unspecified" },
149};
150
151static const char * const languages[] = {
152	"English (US)",
153	"German",
154	"French",
155	"English (UK)",
156	"Spanish",
157	"Italian",
158	"6 (undefined)",
159	"Swiss (French)",
160	"Swiss (German)",
161};
162
163static const char * const dateformat[] = {
164	"MM%cDD%cYY",
165	"DD%cMM%cYY",
166	"YY%cMM%cDD",
167	"YY%cDD%cMM",
168	"4 (undefined)",
169	"5 (undefined)",
170	"6 (undefined)",
171	"7 (undefined)",
172};
173
174static const char * const colors[] = {
175	"2", "4", "16", "256", "65536", "??", "??", "??"
176};
177
178static void atari_nvram_proc_read(unsigned char *nvram, struct seq_file *seq,
179				  void *offset)
180{
181	int checksum;
182	int i;
183	unsigned int vmode;
184
185	spin_lock_irq(&rtc_lock);
186	checksum = __nvram_check_checksum();
187	spin_unlock_irq(&rtc_lock);
188
189	seq_printf(seq, "Checksum status  : %svalid\n", checksum ? "" : "not ");
190
191	seq_puts(seq, "Boot preference  : ");
192	for (i = ARRAY_SIZE(boot_prefs) - 1; i >= 0; --i)
193		if (nvram[1] == boot_prefs[i].val) {
194			seq_printf(seq, "%s\n", boot_prefs[i].name);
195			break;
196		}
197	if (i < 0)
198		seq_printf(seq, "0x%02x (undefined)\n", nvram[1]);
199
200	seq_printf(seq, "SCSI arbitration : %s\n",
201		   (nvram[16] & 0x80) ? "on" : "off");
202	seq_puts(seq, "SCSI host ID     : ");
203	if (nvram[16] & 0x80)
204		seq_printf(seq, "%d\n", nvram[16] & 7);
205	else
206		seq_puts(seq, "n/a\n");
207
208	if (!MACH_IS_FALCON)
209		return;
210
211	seq_puts(seq, "OS language      : ");
212	if (nvram[6] < ARRAY_SIZE(languages))
213		seq_printf(seq, "%s\n", languages[nvram[6]]);
214	else
215		seq_printf(seq, "%u (undefined)\n", nvram[6]);
216	seq_puts(seq, "Keyboard language: ");
217	if (nvram[7] < ARRAY_SIZE(languages))
218		seq_printf(seq, "%s\n", languages[nvram[7]]);
219	else
220		seq_printf(seq, "%u (undefined)\n", nvram[7]);
221	seq_puts(seq, "Date format      : ");
222	seq_printf(seq, dateformat[nvram[8] & 7],
223		   nvram[9] ? nvram[9] : '/', nvram[9] ? nvram[9] : '/');
224	seq_printf(seq, ", %dh clock\n", nvram[8] & 16 ? 24 : 12);
225	seq_puts(seq, "Boot delay       : ");
226	if (nvram[10] == 0)
227		seq_puts(seq, "default\n");
228	else
229		seq_printf(seq, "%ds%s\n", nvram[10],
230			   nvram[10] < 8 ? ", no memory test" : "");
231
232	vmode = (nvram[14] << 8) | nvram[15];
233	seq_printf(seq,
234		   "Video mode       : %s colors, %d columns, %s %s monitor\n",
235		   colors[vmode & 7], vmode & 8 ? 80 : 40,
236		   vmode & 16 ? "VGA" : "TV", vmode & 32 ? "PAL" : "NTSC");
237	seq_printf(seq,
238		   "                   %soverscan, compat. mode %s%s\n",
239		   vmode & 64 ? "" : "no ", vmode & 128 ? "on" : "off",
240		   vmode & 256 ?
241		   (vmode & 16 ? ", line doubling" : ", half screen") : "");
242}
243
244static int nvram_proc_read(struct seq_file *seq, void *offset)
245{
246	unsigned char contents[NVRAM_BYTES];
247	int i;
248
249	spin_lock_irq(&rtc_lock);
250	for (i = 0; i < NVRAM_BYTES; ++i)
251		contents[i] = __nvram_read_byte(i);
252	spin_unlock_irq(&rtc_lock);
253
254	atari_nvram_proc_read(contents, seq, offset);
255
256	return 0;
257}
258
259static int __init atari_nvram_init(void)
260{
261	if (!(MACH_IS_ATARI && ATARIHW_PRESENT(TT_CLK)))
262		return -ENODEV;
263
264	if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read)) {
265		pr_err("nvram: can't create /proc/driver/nvram\n");
266		return -ENOMEM;
267	}
268
269	return 0;
270}
271device_initcall(atari_nvram_init);
272#endif /* CONFIG_PROC_FS */
273