xref: /openbmc/linux/drivers/net/caif/caif_serial.c (revision b159eecc)
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 		ser->tty->port->low_latency << 1;
94 }
95 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
96 {
97 	ser->debugfs_tty_dir = debugfs_create_dir(tty->name, debugfsdir);
98 
99 	debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir,
100 			    &ser->tx_blob);
101 
102 	debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir,
103 			    &ser->rx_blob);
104 
105 	debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir,
106 			   &ser->state);
107 
108 	debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir,
109 			  &ser->tty_status);
110 
111 	ser->tx_blob.data = ser->tx_data;
112 	ser->tx_blob.size = 0;
113 	ser->rx_blob.data = ser->rx_data;
114 	ser->rx_blob.size = 0;
115 }
116 
117 static inline void debugfs_deinit(struct ser_device *ser)
118 {
119 	debugfs_remove_recursive(ser->debugfs_tty_dir);
120 }
121 
122 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
123 {
124 	if (size > sizeof(ser->rx_data))
125 		size = sizeof(ser->rx_data);
126 	memcpy(ser->rx_data, data, size);
127 	ser->rx_blob.data = ser->rx_data;
128 	ser->rx_blob.size = size;
129 }
130 
131 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
132 {
133 	if (size > sizeof(ser->tx_data))
134 		size = sizeof(ser->tx_data);
135 	memcpy(ser->tx_data, data, size);
136 	ser->tx_blob.data = ser->tx_data;
137 	ser->tx_blob.size = size;
138 }
139 #else
140 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
141 {
142 }
143 
144 static inline void debugfs_deinit(struct ser_device *ser)
145 {
146 }
147 
148 static inline void update_tty_status(struct ser_device *ser)
149 {
150 }
151 
152 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
153 {
154 }
155 
156 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
157 {
158 }
159 
160 #endif
161 
162 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
163 			char *flags, int count)
164 {
165 	struct sk_buff *skb = NULL;
166 	struct ser_device *ser;
167 	int ret;
168 
169 	ser = tty->disc_data;
170 
171 	/*
172 	 * NOTE: flags may contain information about break or overrun.
173 	 * This is not yet handled.
174 	 */
175 
176 
177 	/*
178 	 * Workaround for garbage at start of transmission,
179 	 * only enable if STX handling is not enabled.
180 	 */
181 	if (!ser->common.use_stx && !ser->tx_started) {
182 		dev_info(&ser->dev->dev,
183 			"Bytes received before initial transmission -"
184 			"bytes discarded.\n");
185 		return;
186 	}
187 
188 	BUG_ON(ser->dev == NULL);
189 
190 	/* Get a suitable caif packet and copy in data. */
191 	skb = netdev_alloc_skb(ser->dev, count+1);
192 	if (skb == NULL)
193 		return;
194 	skb_put_data(skb, data, count);
195 
196 	skb->protocol = htons(ETH_P_CAIF);
197 	skb_reset_mac_header(skb);
198 	debugfs_rx(ser, data, count);
199 	/* Push received packet up the stack. */
200 	ret = netif_rx_ni(skb);
201 	if (!ret) {
202 		ser->dev->stats.rx_packets++;
203 		ser->dev->stats.rx_bytes += count;
204 	} else
205 		++ser->dev->stats.rx_dropped;
206 	update_tty_status(ser);
207 }
208 
209 static int handle_tx(struct ser_device *ser)
210 {
211 	struct tty_struct *tty;
212 	struct sk_buff *skb;
213 	int tty_wr, len, room;
214 
215 	tty = ser->tty;
216 	ser->tx_started = true;
217 
218 	/* Enter critical section */
219 	if (test_and_set_bit(CAIF_SENDING, &ser->state))
220 		return 0;
221 
222 	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
223 	while ((skb = skb_peek(&ser->head)) != NULL) {
224 
225 		/* Make sure you don't write too much */
226 		len = skb->len;
227 		room = tty_write_room(tty);
228 		if (!room)
229 			break;
230 		if (room > ser_write_chunk)
231 			room = ser_write_chunk;
232 		if (len > room)
233 			len = room;
234 
235 		/* Write to tty or loopback */
236 		if (!ser_loop) {
237 			tty_wr = tty->ops->write(tty, skb->data, len);
238 			update_tty_status(ser);
239 		} else {
240 			tty_wr = len;
241 			ldisc_receive(tty, skb->data, NULL, len);
242 		}
243 		ser->dev->stats.tx_packets++;
244 		ser->dev->stats.tx_bytes += tty_wr;
245 
246 		/* Error on TTY ?! */
247 		if (tty_wr < 0)
248 			goto error;
249 		/* Reduce buffer written, and discard if empty */
250 		skb_pull(skb, tty_wr);
251 		if (skb->len == 0) {
252 			struct sk_buff *tmp = skb_dequeue(&ser->head);
253 			WARN_ON(tmp != skb);
254 			dev_consume_skb_any(skb);
255 		}
256 	}
257 	/* Send flow off if queue is empty */
258 	if (ser->head.qlen <= SEND_QUEUE_LOW &&
259 		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
260 		ser->common.flowctrl != NULL)
261 				ser->common.flowctrl(ser->dev, ON);
262 	clear_bit(CAIF_SENDING, &ser->state);
263 	return 0;
264 error:
265 	clear_bit(CAIF_SENDING, &ser->state);
266 	return tty_wr;
267 }
268 
269 static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev)
270 {
271 	struct ser_device *ser;
272 
273 	if (WARN_ON(!dev))
274 		return -EINVAL;
275 
276 	ser = netdev_priv(dev);
277 
278 	/* Send flow off once, on high water mark */
279 	if (ser->head.qlen > SEND_QUEUE_HIGH &&
280 		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
281 		ser->common.flowctrl != NULL)
282 
283 		ser->common.flowctrl(ser->dev, OFF);
284 
285 	skb_queue_tail(&ser->head, skb);
286 	return handle_tx(ser);
287 }
288 
289 
290 static void ldisc_tx_wakeup(struct tty_struct *tty)
291 {
292 	struct ser_device *ser;
293 
294 	ser = tty->disc_data;
295 	BUG_ON(ser == NULL);
296 	WARN_ON(ser->tty != tty);
297 	handle_tx(ser);
298 }
299 
300 
301 static void ser_release(struct work_struct *work)
302 {
303 	struct list_head list;
304 	struct ser_device *ser, *tmp;
305 
306 	spin_lock(&ser_lock);
307 	list_replace_init(&ser_release_list, &list);
308 	spin_unlock(&ser_lock);
309 
310 	if (!list_empty(&list)) {
311 		rtnl_lock();
312 		list_for_each_entry_safe(ser, tmp, &list, node) {
313 			dev_close(ser->dev);
314 			unregister_netdevice(ser->dev);
315 			debugfs_deinit(ser);
316 		}
317 		rtnl_unlock();
318 	}
319 }
320 
321 static DECLARE_WORK(ser_release_work, ser_release);
322 
323 static int ldisc_open(struct tty_struct *tty)
324 {
325 	struct ser_device *ser;
326 	struct net_device *dev;
327 	char name[64];
328 	int result;
329 
330 	/* No write no play */
331 	if (tty->ops->write == NULL)
332 		return -EOPNOTSUPP;
333 	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
334 		return -EPERM;
335 
336 	/* release devices to avoid name collision */
337 	ser_release(NULL);
338 
339 	result = snprintf(name, sizeof(name), "cf%s", tty->name);
340 	if (result >= IFNAMSIZ)
341 		return -EINVAL;
342 	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
343 			   caifdev_setup);
344 	if (!dev)
345 		return -ENOMEM;
346 
347 	ser = netdev_priv(dev);
348 	ser->tty = tty_kref_get(tty);
349 	ser->dev = dev;
350 	debugfs_init(ser, tty);
351 	tty->receive_room = N_TTY_BUF_SIZE;
352 	tty->disc_data = ser;
353 	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
354 	rtnl_lock();
355 	result = register_netdevice(dev);
356 	if (result) {
357 		rtnl_unlock();
358 		free_netdev(dev);
359 		return -ENODEV;
360 	}
361 
362 	spin_lock(&ser_lock);
363 	list_add(&ser->node, &ser_list);
364 	spin_unlock(&ser_lock);
365 	rtnl_unlock();
366 	netif_stop_queue(dev);
367 	update_tty_status(ser);
368 	return 0;
369 }
370 
371 static void ldisc_close(struct tty_struct *tty)
372 {
373 	struct ser_device *ser = tty->disc_data;
374 
375 	tty_kref_put(ser->tty);
376 
377 	spin_lock(&ser_lock);
378 	list_move(&ser->node, &ser_release_list);
379 	spin_unlock(&ser_lock);
380 	schedule_work(&ser_release_work);
381 }
382 
383 /* The line discipline structure. */
384 static struct tty_ldisc_ops caif_ldisc = {
385 	.owner =	THIS_MODULE,
386 	.magic =	TTY_LDISC_MAGIC,
387 	.name =		"n_caif",
388 	.open =		ldisc_open,
389 	.close =	ldisc_close,
390 	.receive_buf =	ldisc_receive,
391 	.write_wakeup =	ldisc_tx_wakeup
392 };
393 
394 static int register_ldisc(void)
395 {
396 	int result;
397 
398 	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
399 	if (result < 0) {
400 		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
401 			result);
402 		return result;
403 	}
404 	return result;
405 }
406 static const struct net_device_ops netdev_ops = {
407 	.ndo_open = caif_net_open,
408 	.ndo_stop = caif_net_close,
409 	.ndo_start_xmit = caif_xmit
410 };
411 
412 static void caifdev_setup(struct net_device *dev)
413 {
414 	struct ser_device *serdev = netdev_priv(dev);
415 
416 	dev->features = 0;
417 	dev->netdev_ops = &netdev_ops;
418 	dev->type = ARPHRD_CAIF;
419 	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
420 	dev->mtu = CAIF_MAX_MTU;
421 	dev->priv_flags |= IFF_NO_QUEUE;
422 	dev->needs_free_netdev = true;
423 	skb_queue_head_init(&serdev->head);
424 	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
425 	serdev->common.use_frag = true;
426 	serdev->common.use_stx = ser_use_stx;
427 	serdev->common.use_fcs = ser_use_fcs;
428 	serdev->dev = dev;
429 }
430 
431 
432 static int caif_net_open(struct net_device *dev)
433 {
434 	netif_wake_queue(dev);
435 	return 0;
436 }
437 
438 static int caif_net_close(struct net_device *dev)
439 {
440 	netif_stop_queue(dev);
441 	return 0;
442 }
443 
444 static int __init caif_ser_init(void)
445 {
446 	int ret;
447 
448 	ret = register_ldisc();
449 	debugfsdir = debugfs_create_dir("caif_serial", NULL);
450 	return ret;
451 }
452 
453 static void __exit caif_ser_exit(void)
454 {
455 	spin_lock(&ser_lock);
456 	list_splice(&ser_list, &ser_release_list);
457 	spin_unlock(&ser_lock);
458 	ser_release(NULL);
459 	cancel_work_sync(&ser_release_work);
460 	tty_unregister_ldisc(N_CAIF);
461 	debugfs_remove_recursive(debugfsdir);
462 }
463 
464 module_init(caif_ser_init);
465 module_exit(caif_ser_exit);
466