xref: /openbmc/linux/drivers/s390/char/sclp_con.c (revision 4ae46db9)
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