nvram.c

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