1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * SCLP line mode console driver
4 *
5 * Copyright IBM Corp. 1999, 2009
6 * Author(s): Martin Peschke <mpeschke@de.ibm.com>
7 * Martin Schwidefsky <schwidefsky@de.ibm.com>
8 */
9
10 #include <linux/kmod.h>
11 #include <linux/console.h>
12 #include <linux/init.h>
13 #include <linux/panic_notifier.h>
14 #include <linux/timer.h>
15 #include <linux/jiffies.h>
16 #include <linux/termios.h>
17 #include <linux/err.h>
18 #include <linux/reboot.h>
19 #include <linux/gfp.h>
20
21 #include "sclp.h"
22 #include "sclp_rw.h"
23 #include "sclp_tty.h"
24
25 #define sclp_console_major 4 /* TTYAUX_MAJOR */
26 #define sclp_console_minor 64
27 #define sclp_console_name "ttyS"
28
29 /* Lock to guard over changes to global variables */
30 static DEFINE_SPINLOCK(sclp_con_lock);
31 /* List of free pages that can be used for console output buffering */
32 static LIST_HEAD(sclp_con_pages);
33 /* List of full struct sclp_buffer structures ready for output */
34 static LIST_HEAD(sclp_con_outqueue);
35 /* Pointer to current console buffer */
36 static struct sclp_buffer *sclp_conbuf;
37 /* Timer for delayed output of console messages */
38 static struct timer_list sclp_con_timer;
39 /* Flag that output queue is currently running */
40 static int sclp_con_queue_running;
41
42 /* Output format for console messages */
43 #define SCLP_CON_COLUMNS 320
44 #define SPACES_PER_TAB 8
45
46 static void
sclp_conbuf_callback(struct sclp_buffer * buffer,int rc)47 sclp_conbuf_callback(struct sclp_buffer *buffer, int rc)
48 {
49 unsigned long flags;
50 void *page;
51
52 do {
53 page = sclp_unmake_buffer(buffer);
54 spin_lock_irqsave(&sclp_con_lock, flags);
55
56 /* Remove buffer from outqueue */
57 list_del(&buffer->list);
58 list_add_tail((struct list_head *) page, &sclp_con_pages);
59
60 /* Check if there is a pending buffer on the out queue. */
61 buffer = NULL;
62 if (!list_empty(&sclp_con_outqueue))
63 buffer = list_first_entry(&sclp_con_outqueue,
64 struct sclp_buffer, list);
65 if (!buffer) {
66 sclp_con_queue_running = 0;
67 spin_unlock_irqrestore(&sclp_con_lock, flags);
68 break;
69 }
70 spin_unlock_irqrestore(&sclp_con_lock, flags);
71 } while (sclp_emit_buffer(buffer, sclp_conbuf_callback));
72 }
73
74 /*
75 * Finalize and emit first pending buffer.
76 */
sclp_conbuf_emit(void)77 static void sclp_conbuf_emit(void)
78 {
79 struct sclp_buffer* buffer;
80 unsigned long flags;
81 int rc;
82
83 spin_lock_irqsave(&sclp_con_lock, flags);
84 if (sclp_conbuf)
85 list_add_tail(&sclp_conbuf->list, &sclp_con_outqueue);
86 sclp_conbuf = NULL;
87 if (sclp_con_queue_running)
88 goto out_unlock;
89 if (list_empty(&sclp_con_outqueue))
90 goto out_unlock;
91 buffer = list_first_entry(&sclp_con_outqueue, struct sclp_buffer,
92 list);
93 sclp_con_queue_running = 1;
94 spin_unlock_irqrestore(&sclp_con_lock, flags);
95
96 rc = sclp_emit_buffer(buffer, sclp_conbuf_callback);
97 if (rc)
98 sclp_conbuf_callback(buffer, rc);
99 return;
100 out_unlock:
101 spin_unlock_irqrestore(&sclp_con_lock, flags);
102 }
103
104 /*
105 * Wait until out queue is empty
106 */
sclp_console_sync_queue(void)107 static void sclp_console_sync_queue(void)
108 {
109 unsigned long flags;
110
111 spin_lock_irqsave(&sclp_con_lock, flags);
112 del_timer(&sclp_con_timer);
113 while (sclp_con_queue_running) {
114 spin_unlock_irqrestore(&sclp_con_lock, flags);
115 sclp_sync_wait();
116 spin_lock_irqsave(&sclp_con_lock, flags);
117 }
118 spin_unlock_irqrestore(&sclp_con_lock, flags);
119 }
120
121 /*
122 * When this routine is called from the timer then we flush the
123 * temporary write buffer without further waiting on a final new line.
124 */
125 static void
sclp_console_timeout(struct timer_list * unused)126 sclp_console_timeout(struct timer_list *unused)
127 {
128 sclp_conbuf_emit();
129 }
130
131 /*
132 * Drop oldest console buffer if sclp_con_drop is set
133 */
134 static int
sclp_console_drop_buffer(void)135 sclp_console_drop_buffer(void)
136 {
137 struct list_head *list;
138 struct sclp_buffer *buffer;
139 void *page;
140
141 if (!sclp_console_drop)
142 return 0;
143 list = sclp_con_outqueue.next;
144 if (sclp_con_queue_running)
145 /* The first element is in I/O */
146 list = list->next;
147 if (list == &sclp_con_outqueue)
148 return 0;
149 list_del(list);
150 buffer = list_entry(list, struct sclp_buffer, list);
151 page = sclp_unmake_buffer(buffer);
152 list_add_tail((struct list_head *) page, &sclp_con_pages);
153 return 1;
154 }
155
156 /*
157 * Writes the given message to S390 system console
158 */
159 static void
sclp_console_write(struct console * console,const char * message,unsigned int count)160 sclp_console_write(struct console *console, const char *message,
161 unsigned int count)
162 {
163 unsigned long flags;
164 void *page;
165 int written;
166
167 if (count == 0)
168 return;
169 spin_lock_irqsave(&sclp_con_lock, flags);
170 /*
171 * process escape characters, write message into buffer,
172 * send buffer to SCLP
173 */
174 do {
175 /* make sure we have a console output buffer */
176 if (sclp_conbuf == NULL) {
177 if (list_empty(&sclp_con_pages))
178 sclp_console_full++;
179 while (list_empty(&sclp_con_pages)) {
180 if (sclp_console_drop_buffer())
181 break;
182 spin_unlock_irqrestore(&sclp_con_lock, flags);
183 sclp_sync_wait();
184 spin_lock_irqsave(&sclp_con_lock, flags);
185 }
186 page = sclp_con_pages.next;
187 list_del((struct list_head *) page);
188 sclp_conbuf = sclp_make_buffer(page, SCLP_CON_COLUMNS,
189 SPACES_PER_TAB);
190 }
191 /* try to write the string to the current output buffer */
192 written = sclp_write(sclp_conbuf, (const unsigned char *)
193 message, count);
194 if (written == count)
195 break;
196 /*
197 * Not all characters could be written to the current
198 * output buffer. Emit the buffer, create a new buffer
199 * and then output the rest of the string.
200 */
201 spin_unlock_irqrestore(&sclp_con_lock, flags);
202 sclp_conbuf_emit();
203 spin_lock_irqsave(&sclp_con_lock, flags);
204 message += written;
205 count -= written;
206 } while (count > 0);
207 /* Setup timer to output current console buffer after 1/10 second */
208 if (sclp_conbuf != NULL && sclp_chars_in_buffer(sclp_conbuf) != 0 &&
209 !timer_pending(&sclp_con_timer)) {
210 mod_timer(&sclp_con_timer, jiffies + HZ / 10);
211 }
212 spin_unlock_irqrestore(&sclp_con_lock, flags);
213 }
214
215 static struct tty_driver *
sclp_console_device(struct console * c,int * index)216 sclp_console_device(struct console *c, int *index)
217 {
218 *index = c->index;
219 return sclp_tty_driver;
220 }
221
222 /*
223 * This panic/reboot notifier makes sure that all buffers
224 * will be flushed to the SCLP.
225 */
sclp_console_notify(struct notifier_block * self,unsigned long event,void * data)226 static int sclp_console_notify(struct notifier_block *self,
227 unsigned long event, void *data)
228 {
229 /*
230 * Perform the lock check before effectively getting the
231 * lock on sclp_conbuf_emit() / sclp_console_sync_queue()
232 * to prevent potential lockups in atomic context.
233 */
234 if (spin_is_locked(&sclp_con_lock))
235 return NOTIFY_DONE;
236
237 sclp_conbuf_emit();
238 sclp_console_sync_queue();
239
240 return NOTIFY_DONE;
241 }
242
243 static struct notifier_block on_panic_nb = {
244 .notifier_call = sclp_console_notify,
245 .priority = INT_MIN + 1, /* run the callback late */
246 };
247
248 static struct notifier_block on_reboot_nb = {
249 .notifier_call = sclp_console_notify,
250 .priority = INT_MIN + 1, /* run the callback late */
251 };
252
253 /*
254 * used to register the SCLP console to the kernel and to
255 * give printk necessary information
256 */
257 static struct console sclp_console =
258 {
259 .name = sclp_console_name,
260 .write = sclp_console_write,
261 .device = sclp_console_device,
262 .flags = CON_PRINTBUFFER,
263 .index = 0 /* ttyS0 */
264 };
265
266 /*
267 * called by console_init() in drivers/char/tty_io.c at boot-time.
268 */
269 static int __init
sclp_console_init(void)270 sclp_console_init(void)
271 {
272 void *page;
273 int i;
274 int rc;
275
276 /* SCLP consoles are handled together */
277 if (!(CONSOLE_IS_SCLP || CONSOLE_IS_VT220))
278 return 0;
279 rc = sclp_rw_init();
280 if (rc)
281 return rc;
282 /* Allocate pages for output buffering */
283 for (i = 0; i < sclp_console_pages; i++) {
284 page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
285 list_add_tail(page, &sclp_con_pages);
286 }
287 sclp_conbuf = NULL;
288 timer_setup(&sclp_con_timer, sclp_console_timeout, 0);
289
290 /* enable printk-access to this driver */
291 atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
292 register_reboot_notifier(&on_reboot_nb);
293 register_console(&sclp_console);
294 return 0;
295 }
296
297 console_initcall(sclp_console_init);
298