xref: /linux/drivers/net/caif/caif_serial.c (revision a1c3be890440a1769ed6f822376a3e3ab0d42994) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) ST-Ericsson AB 2010
4  * Author:	Sjur Brendeland
5  */
6 
7 #include <linux/hardirq.h>
8 #include <linux/init.h>
9 #include <linux/module.h>
10 #include <linux/device.h>
11 #include <linux/types.h>
12 #include <linux/skbuff.h>
13 #include <linux/netdevice.h>
14 #include <linux/rtnetlink.h>
15 #include <linux/tty.h>
16 #include <linux/file.h>
17 #include <linux/if_arp.h>
18 #include <net/caif/caif_device.h>
19 #include <net/caif/cfcnfg.h>
20 #include <linux/err.h>
21 #include <linux/debugfs.h>
22 
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Sjur Brendeland");
25 MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
26 MODULE_LICENSE("GPL");
27 MODULE_ALIAS_LDISC(N_CAIF);
28 
29 #define SEND_QUEUE_LOW 10
30 #define SEND_QUEUE_HIGH 100
31 #define CAIF_SENDING	        1 /* Bit 1 = 0x02*/
32 #define CAIF_FLOW_OFF_SENT	4 /* Bit 4 = 0x10 */
33 #define MAX_WRITE_CHUNK	     4096
34 #define ON 1
35 #define OFF 0
36 #define CAIF_MAX_MTU 4096
37 
38 static DEFINE_SPINLOCK(ser_lock);
39 static LIST_HEAD(ser_list);
40 static LIST_HEAD(ser_release_list);
41 
42 static bool ser_loop;
43 module_param(ser_loop, bool, 0444);
44 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
45 
46 static bool ser_use_stx = true;
47 module_param(ser_use_stx, bool, 0444);
48 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
49 
50 static bool ser_use_fcs = true;
51 
52 module_param(ser_use_fcs, bool, 0444);
53 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
54 
55 static int ser_write_chunk = MAX_WRITE_CHUNK;
56 module_param(ser_write_chunk, int, 0444);
57 
58 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
59 
60 static struct dentry *debugfsdir;
61 
62 static int caif_net_open(struct net_device *dev);
63 static int caif_net_close(struct net_device *dev);
64 
65 struct ser_device {
66 	struct caif_dev_common common;
67 	struct list_head node;
68 	struct net_device *dev;
69 	struct sk_buff_head head;
70 	struct tty_struct *tty;
71 	bool tx_started;
72 	unsigned long state;
73 #ifdef CONFIG_DEBUG_FS
74 	struct dentry *debugfs_tty_dir;
75 	struct debugfs_blob_wrapper tx_blob;
76 	struct debugfs_blob_wrapper rx_blob;
77 	u8 rx_data[128];
78 	u8 tx_data[128];
79 	u8 tty_status;
80 
81 #endif
82 };
83 
84 static void caifdev_setup(struct net_device *dev);
85 static void ldisc_tx_wakeup(struct tty_struct *tty);
86 #ifdef CONFIG_DEBUG_FS
87 static inline void update_tty_status(struct ser_device *ser)
88 {
89 	ser->tty_status =
90 		ser->tty->stopped << 5 |
91 		ser->tty->flow_stopped << 3 |
92 		ser->tty->packet << 2;
93 }
94 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
95 {
96 	ser->debugfs_tty_dir = debugfs_create_dir(tty->name, debugfsdir);
97 
98 	debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir,
99 			    &ser->tx_blob);
100 
101 	debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir,
102 			    &ser->rx_blob);
103 
104 	debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir,
105 			   &ser->state);
106 
107 	debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir,
108 			  &ser->tty_status);
109 
110 	ser->tx_blob.data = ser->tx_data;
111 	ser->tx_blob.size = 0;
112 	ser->rx_blob.data = ser->rx_data;
113 	ser->rx_blob.size = 0;
114 }
115 
116 static inline void debugfs_deinit(struct ser_device *ser)
117 {
118 	debugfs_remove_recursive(ser->debugfs_tty_dir);
119 }
120 
121 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
122 {
123 	if (size > sizeof(ser->rx_data))
124 		size = sizeof(ser->rx_data);
125 	memcpy(ser->rx_data, data, size);
126 	ser->rx_blob.data = ser->rx_data;
127 	ser->rx_blob.size = size;
128 }
129 
130 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
131 {
132 	if (size > sizeof(ser->tx_data))
133 		size = sizeof(ser->tx_data);
134 	memcpy(ser->tx_data, data, size);
135 	ser->tx_blob.data = ser->tx_data;
136 	ser->tx_blob.size = size;
137 }
138 #else
139 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
140 {
141 }
142 
143 static inline void debugfs_deinit(struct ser_device *ser)
144 {
145 }
146 
147 static inline void update_tty_status(struct ser_device *ser)
148 {
149 }
150 
151 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
152 {
153 }
154 
155 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
156 {
157 }
158 
159 #endif
160 
161 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
162 			char *flags, int count)
163 {
164 	struct sk_buff *skb = NULL;
165 	struct ser_device *ser;
166 	int ret;
167 
168 	ser = tty->disc_data;
169 
170 	/*
171 	 * NOTE: flags may contain information about break or overrun.
172 	 * This is not yet handled.
173 	 */
174 
175 
176 	/*
177 	 * Workaround for garbage at start of transmission,
178 	 * only enable if STX handling is not enabled.
179 	 */
180 	if (!ser->common.use_stx && !ser->tx_started) {
181 		dev_info(&ser->dev->dev,
182 			"Bytes received before initial transmission -"
183 			"bytes discarded.\n");
184 		return;
185 	}
186 
187 	BUG_ON(ser->dev == NULL);
188 
189 	/* Get a suitable caif packet and copy in data. */
190 	skb = netdev_alloc_skb(ser->dev, count+1);
191 	if (skb == NULL)
192 		return;
193 	skb_put_data(skb, data, count);
194 
195 	skb->protocol = htons(ETH_P_CAIF);
196 	skb_reset_mac_header(skb);
197 	debugfs_rx(ser, data, count);
198 	/* Push received packet up the stack. */
199 	ret = netif_rx_ni(skb);
200 	if (!ret) {
201 		ser->dev->stats.rx_packets++;
202 		ser->dev->stats.rx_bytes += count;
203 	} else
204 		++ser->dev->stats.rx_dropped;
205 	update_tty_status(ser);
206 }
207 
208 static int handle_tx(struct ser_device *ser)
209 {
210 	struct tty_struct *tty;
211 	struct sk_buff *skb;
212 	int tty_wr, len, room;
213 
214 	tty = ser->tty;
215 	ser->tx_started = true;
216 
217 	/* Enter critical section */
218 	if (test_and_set_bit(CAIF_SENDING, &ser->state))
219 		return 0;
220 
221 	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
222 	while ((skb = skb_peek(&ser->head)) != NULL) {
223 
224 		/* Make sure you don't write too much */
225 		len = skb->len;
226 		room = tty_write_room(tty);
227 		if (!room)
228 			break;
229 		if (room > ser_write_chunk)
230 			room = ser_write_chunk;
231 		if (len > room)
232 			len = room;
233 
234 		/* Write to tty or loopback */
235 		if (!ser_loop) {
236 			tty_wr = tty->ops->write(tty, skb->data, len);
237 			update_tty_status(ser);
238 		} else {
239 			tty_wr = len;
240 			ldisc_receive(tty, skb->data, NULL, len);
241 		}
242 		ser->dev->stats.tx_packets++;
243 		ser->dev->stats.tx_bytes += tty_wr;
244 
245 		/* Error on TTY ?! */
246 		if (tty_wr < 0)
247 			goto error;
248 		/* Reduce buffer written, and discard if empty */
249 		skb_pull(skb, tty_wr);
250 		if (skb->len == 0) {
251 			struct sk_buff *tmp = skb_dequeue(&ser->head);
252 			WARN_ON(tmp != skb);
253 			dev_consume_skb_any(skb);
254 		}
255 	}
256 	/* Send flow off if queue is empty */
257 	if (ser->head.qlen <= SEND_QUEUE_LOW &&
258 		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
259 		ser->common.flowctrl != NULL)
260 				ser->common.flowctrl(ser->dev, ON);
261 	clear_bit(CAIF_SENDING, &ser->state);
262 	return 0;
263 error:
264 	clear_bit(CAIF_SENDING, &ser->state);
265 	return tty_wr;
266 }
267 
268 static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev)
269 {
270 	struct ser_device *ser;
271 
272 	if (WARN_ON(!dev))
273 		return -EINVAL;
274 
275 	ser = netdev_priv(dev);
276 
277 	/* Send flow off once, on high water mark */
278 	if (ser->head.qlen > SEND_QUEUE_HIGH &&
279 		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
280 		ser->common.flowctrl != NULL)
281 
282 		ser->common.flowctrl(ser->dev, OFF);
283 
284 	skb_queue_tail(&ser->head, skb);
285 	return handle_tx(ser);
286 }
287 
288 
289 static void ldisc_tx_wakeup(struct tty_struct *tty)
290 {
291 	struct ser_device *ser;
292 
293 	ser = tty->disc_data;
294 	BUG_ON(ser == NULL);
295 	WARN_ON(ser->tty != tty);
296 	handle_tx(ser);
297 }
298 
299 
300 static void ser_release(struct work_struct *work)
301 {
302 	struct list_head list;
303 	struct ser_device *ser, *tmp;
304 
305 	spin_lock(&ser_lock);
306 	list_replace_init(&ser_release_list, &list);
307 	spin_unlock(&ser_lock);
308 
309 	if (!list_empty(&list)) {
310 		rtnl_lock();
311 		list_for_each_entry_safe(ser, tmp, &list, node) {
312 			dev_close(ser->dev);
313 			unregister_netdevice(ser->dev);
314 			debugfs_deinit(ser);
315 		}
316 		rtnl_unlock();
317 	}
318 }
319 
320 static DECLARE_WORK(ser_release_work, ser_release);
321 
322 static int ldisc_open(struct tty_struct *tty)
323 {
324 	struct ser_device *ser;
325 	struct net_device *dev;
326 	char name[64];
327 	int result;
328 
329 	/* No write no play */
330 	if (tty->ops->write == NULL)
331 		return -EOPNOTSUPP;
332 	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
333 		return -EPERM;
334 
335 	/* release devices to avoid name collision */
336 	ser_release(NULL);
337 
338 	result = snprintf(name, sizeof(name), "cf%s", tty->name);
339 	if (result >= IFNAMSIZ)
340 		return -EINVAL;
341 	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
342 			   caifdev_setup);
343 	if (!dev)
344 		return -ENOMEM;
345 
346 	ser = netdev_priv(dev);
347 	ser->tty = tty_kref_get(tty);
348 	ser->dev = dev;
349 	debugfs_init(ser, tty);
350 	tty->receive_room = N_TTY_BUF_SIZE;
351 	tty->disc_data = ser;
352 	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
353 	rtnl_lock();
354 	result = register_netdevice(dev);
355 	if (result) {
356 		rtnl_unlock();
357 		free_netdev(dev);
358 		return -ENODEV;
359 	}
360 
361 	spin_lock(&ser_lock);
362 	list_add(&ser->node, &ser_list);
363 	spin_unlock(&ser_lock);
364 	rtnl_unlock();
365 	netif_stop_queue(dev);
366 	update_tty_status(ser);
367 	return 0;
368 }
369 
370 static void ldisc_close(struct tty_struct *tty)
371 {
372 	struct ser_device *ser = tty->disc_data;
373 
374 	tty_kref_put(ser->tty);
375 
376 	spin_lock(&ser_lock);
377 	list_move(&ser->node, &ser_release_list);
378 	spin_unlock(&ser_lock);
379 	schedule_work(&ser_release_work);
380 }
381 
382 /* The line discipline structure. */
383 static struct tty_ldisc_ops caif_ldisc = {
384 	.owner =	THIS_MODULE,
385 	.magic =	TTY_LDISC_MAGIC,
386 	.name =		"n_caif",
387 	.open =		ldisc_open,
388 	.close =	ldisc_close,
389 	.receive_buf =	ldisc_receive,
390 	.write_wakeup =	ldisc_tx_wakeup
391 };
392 
393 static int register_ldisc(void)
394 {
395 	int result;
396 
397 	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
398 	if (result < 0) {
399 		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
400 			result);
401 		return result;
402 	}
403 	return result;
404 }
405 static const struct net_device_ops netdev_ops = {
406 	.ndo_open = caif_net_open,
407 	.ndo_stop = caif_net_close,
408 	.ndo_start_xmit = caif_xmit
409 };
410 
411 static void caifdev_setup(struct net_device *dev)
412 {
413 	struct ser_device *serdev = netdev_priv(dev);
414 
415 	dev->features = 0;
416 	dev->netdev_ops = &netdev_ops;
417 	dev->type = ARPHRD_CAIF;
418 	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
419 	dev->mtu = CAIF_MAX_MTU;
420 	dev->priv_flags |= IFF_NO_QUEUE;
421 	dev->needs_free_netdev = true;
422 	skb_queue_head_init(&serdev->head);
423 	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
424 	serdev->common.use_frag = true;
425 	serdev->common.use_stx = ser_use_stx;
426 	serdev->common.use_fcs = ser_use_fcs;
427 	serdev->dev = dev;
428 }
429 
430 
431 static int caif_net_open(struct net_device *dev)
432 {
433 	netif_wake_queue(dev);
434 	return 0;
435 }
436 
437 static int caif_net_close(struct net_device *dev)
438 {
439 	netif_stop_queue(dev);
440 	return 0;
441 }
442 
443 static int __init caif_ser_init(void)
444 {
445 	int ret;
446 
447 	ret = register_ldisc();
448 	debugfsdir = debugfs_create_dir("caif_serial", NULL);
449 	return ret;
450 }
451 
452 static void __exit caif_ser_exit(void)
453 {
454 	spin_lock(&ser_lock);
455 	list_splice(&ser_list, &ser_release_list);
456 	spin_unlock(&ser_lock);
457 	ser_release(NULL);
458 	cancel_work_sync(&ser_release_work);
459 	tty_unregister_ldisc(N_CAIF);
460 	debugfs_remove_recursive(debugfsdir);
461 }
462 
463 module_init(caif_ser_init);
464 module_exit(caif_ser_exit);
465