xref: /openbmc/linux/drivers/tty/ehv_bytechan.c (revision 95713967)
1 // SPDX-License-Identifier: GPL-2.0
2 /* ePAPR hypervisor byte channel device driver
3  *
4  * Copyright 2009-2011 Freescale Semiconductor, Inc.
5  *
6  * Author: Timur Tabi <timur@freescale.com>
7  *
8  * This driver support three distinct interfaces, all of which are related to
9  * ePAPR hypervisor byte channels.
10  *
11  * 1) An early-console (udbg) driver.  This provides early console output
12  * through a byte channel.  The byte channel handle must be specified in a
13  * Kconfig option.
14  *
15  * 2) A normal console driver.  Output is sent to the byte channel designated
16  * for stdout in the device tree.  The console driver is for handling kernel
17  * printk calls.
18  *
19  * 3) A tty driver, which is used to handle user-space input and output.  The
20  * byte channel used for the console is designated as the default tty.
21  */
22 
23 #include <linux/init.h>
24 #include <linux/slab.h>
25 #include <linux/err.h>
26 #include <linux/interrupt.h>
27 #include <linux/fs.h>
28 #include <linux/poll.h>
29 #include <asm/epapr_hcalls.h>
30 #include <linux/of.h>
31 #include <linux/of_irq.h>
32 #include <linux/platform_device.h>
33 #include <linux/cdev.h>
34 #include <linux/console.h>
35 #include <linux/tty.h>
36 #include <linux/tty_flip.h>
37 #include <linux/circ_buf.h>
38 #include <asm/udbg.h>
39 
40 /* The size of the transmit circular buffer.  This must be a power of two. */
41 #define BUF_SIZE	2048
42 
43 /* Per-byte channel private data */
44 struct ehv_bc_data {
45 	struct device *dev;
46 	struct tty_port port;
47 	uint32_t handle;
48 	unsigned int rx_irq;
49 	unsigned int tx_irq;
50 
51 	spinlock_t lock;	/* lock for transmit buffer */
52 	unsigned char buf[BUF_SIZE];	/* transmit circular buffer */
53 	unsigned int head;	/* circular buffer head */
54 	unsigned int tail;	/* circular buffer tail */
55 
56 	int tx_irq_enabled;	/* true == TX interrupt is enabled */
57 };
58 
59 /* Array of byte channel objects */
60 static struct ehv_bc_data *bcs;
61 
62 /* Byte channel handle for stdout (and stdin), taken from device tree */
63 static unsigned int stdout_bc;
64 
65 /* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
66 static unsigned int stdout_irq;
67 
68 /**************************** SUPPORT FUNCTIONS ****************************/
69 
70 /*
71  * Enable the transmit interrupt
72  *
73  * Unlike a serial device, byte channels have no mechanism for disabling their
74  * own receive or transmit interrupts.  To emulate that feature, we toggle
75  * the IRQ in the kernel.
76  *
77  * We cannot just blindly call enable_irq() or disable_irq(), because these
78  * calls are reference counted.  This means that we cannot call enable_irq()
79  * if interrupts are already enabled.  This can happen in two situations:
80  *
81  * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
82  * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
83  *
84  * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
85  */
enable_tx_interrupt(struct ehv_bc_data * bc)86 static void enable_tx_interrupt(struct ehv_bc_data *bc)
87 {
88 	if (!bc->tx_irq_enabled) {
89 		enable_irq(bc->tx_irq);
90 		bc->tx_irq_enabled = 1;
91 	}
92 }
93 
disable_tx_interrupt(struct ehv_bc_data * bc)94 static void disable_tx_interrupt(struct ehv_bc_data *bc)
95 {
96 	if (bc->tx_irq_enabled) {
97 		disable_irq_nosync(bc->tx_irq);
98 		bc->tx_irq_enabled = 0;
99 	}
100 }
101 
102 /*
103  * find the byte channel handle to use for the console
104  *
105  * The byte channel to be used for the console is specified via a "stdout"
106  * property in the /chosen node.
107  */
find_console_handle(void)108 static int find_console_handle(void)
109 {
110 	struct device_node *np = of_stdout;
111 	const uint32_t *iprop;
112 
113 	/* We don't care what the aliased node is actually called.  We only
114 	 * care if it's compatible with "epapr,hv-byte-channel", because that
115 	 * indicates that it's a byte channel node.
116 	 */
117 	if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel"))
118 		return 0;
119 
120 	stdout_irq = irq_of_parse_and_map(np, 0);
121 	if (!stdout_irq) {
122 		pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np);
123 		return 0;
124 	}
125 
126 	/*
127 	 * The 'hv-handle' property contains the handle for this byte channel.
128 	 */
129 	iprop = of_get_property(np, "hv-handle", NULL);
130 	if (!iprop) {
131 		pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n",
132 		       np);
133 		return 0;
134 	}
135 	stdout_bc = be32_to_cpu(*iprop);
136 	return 1;
137 }
138 
local_ev_byte_channel_send(unsigned int handle,unsigned int * count,const char * p)139 static unsigned int local_ev_byte_channel_send(unsigned int handle,
140 					       unsigned int *count,
141 					       const char *p)
142 {
143 	char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
144 	unsigned int c = *count;
145 
146 	if (c < sizeof(buffer)) {
147 		memcpy(buffer, p, c);
148 		memset(&buffer[c], 0, sizeof(buffer) - c);
149 		p = buffer;
150 	}
151 	return ev_byte_channel_send(handle, count, p);
152 }
153 
154 /*************************** EARLY CONSOLE DRIVER ***************************/
155 
156 #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
157 
158 /*
159  * send a byte to a byte channel, wait if necessary
160  *
161  * This function sends a byte to a byte channel, and it waits and
162  * retries if the byte channel is full.  It returns if the character
163  * has been sent, or if some error has occurred.
164  *
165  */
byte_channel_spin_send(const char data)166 static void byte_channel_spin_send(const char data)
167 {
168 	int ret, count;
169 
170 	do {
171 		count = 1;
172 		ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
173 					   &count, &data);
174 	} while (ret == EV_EAGAIN);
175 }
176 
177 /*
178  * The udbg subsystem calls this function to display a single character.
179  * We convert CR to a CR/LF.
180  */
ehv_bc_udbg_putc(char c)181 static void ehv_bc_udbg_putc(char c)
182 {
183 	if (c == '\n')
184 		byte_channel_spin_send('\r');
185 
186 	byte_channel_spin_send(c);
187 }
188 
189 /*
190  * early console initialization
191  *
192  * PowerPC kernels support an early printk console, also known as udbg.
193  * This function must be called via the ppc_md.init_early function pointer.
194  * At this point, the device tree has been unflattened, so we can obtain the
195  * byte channel handle for stdout.
196  *
197  * We only support displaying of characters (putc).  We do not support
198  * keyboard input.
199  */
udbg_init_ehv_bc(void)200 void __init udbg_init_ehv_bc(void)
201 {
202 	unsigned int rx_count, tx_count;
203 	unsigned int ret;
204 
205 	/* Verify the byte channel handle */
206 	ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
207 				   &rx_count, &tx_count);
208 	if (ret)
209 		return;
210 
211 	udbg_putc = ehv_bc_udbg_putc;
212 	register_early_udbg_console();
213 
214 	udbg_printf("ehv-bc: early console using byte channel handle %u\n",
215 		    CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
216 }
217 
218 #endif
219 
220 /****************************** CONSOLE DRIVER ******************************/
221 
222 static struct tty_driver *ehv_bc_driver;
223 
224 /*
225  * Byte channel console sending worker function.
226  *
227  * For consoles, if the output buffer is full, we should just spin until it
228  * clears.
229  */
ehv_bc_console_byte_channel_send(unsigned int handle,const char * s,unsigned int count)230 static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
231 			     unsigned int count)
232 {
233 	unsigned int len;
234 	int ret = 0;
235 
236 	while (count) {
237 		len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
238 		do {
239 			ret = local_ev_byte_channel_send(handle, &len, s);
240 		} while (ret == EV_EAGAIN);
241 		count -= len;
242 		s += len;
243 	}
244 
245 	return ret;
246 }
247 
248 /*
249  * write a string to the console
250  *
251  * This function gets called to write a string from the kernel, typically from
252  * a printk().  This function spins until all data is written.
253  *
254  * We copy the data to a temporary buffer because we need to insert a \r in
255  * front of every \n.  It's more efficient to copy the data to the buffer than
256  * it is to make multiple hcalls for each character or each newline.
257  */
ehv_bc_console_write(struct console * co,const char * s,unsigned int count)258 static void ehv_bc_console_write(struct console *co, const char *s,
259 				 unsigned int count)
260 {
261 	char s2[EV_BYTE_CHANNEL_MAX_BYTES];
262 	unsigned int i, j = 0;
263 	char c;
264 
265 	for (i = 0; i < count; i++) {
266 		c = *s++;
267 
268 		if (c == '\n')
269 			s2[j++] = '\r';
270 
271 		s2[j++] = c;
272 		if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
273 			if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
274 				return;
275 			j = 0;
276 		}
277 	}
278 
279 	if (j)
280 		ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
281 }
282 
283 /*
284  * When /dev/console is opened, the kernel iterates the console list looking
285  * for one with ->device and then calls that method. On success, it expects
286  * the passed-in int* to contain the minor number to use.
287  */
ehv_bc_console_device(struct console * co,int * index)288 static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
289 {
290 	*index = co->index;
291 
292 	return ehv_bc_driver;
293 }
294 
295 static struct console ehv_bc_console = {
296 	.name		= "ttyEHV",
297 	.write		= ehv_bc_console_write,
298 	.device		= ehv_bc_console_device,
299 	.flags		= CON_PRINTBUFFER | CON_ENABLED,
300 };
301 
302 /*
303  * Console initialization
304  *
305  * This is the first function that is called after the device tree is
306  * available, so here is where we determine the byte channel handle and IRQ for
307  * stdout/stdin, even though that information is used by the tty and character
308  * drivers.
309  */
ehv_bc_console_init(void)310 static int __init ehv_bc_console_init(void)
311 {
312 	if (!find_console_handle()) {
313 		pr_debug("ehv-bc: stdout is not a byte channel\n");
314 		return -ENODEV;
315 	}
316 
317 #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
318 	/* Print a friendly warning if the user chose the wrong byte channel
319 	 * handle for udbg.
320 	 */
321 	if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
322 		pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n",
323 			CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
324 #endif
325 
326 	/* add_preferred_console() must be called before register_console(),
327 	   otherwise it won't work.  However, we don't want to enumerate all the
328 	   byte channels here, either, since we only care about one. */
329 
330 	add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
331 	register_console(&ehv_bc_console);
332 
333 	pr_info("ehv-bc: registered console driver for byte channel %u\n",
334 		stdout_bc);
335 
336 	return 0;
337 }
338 console_initcall(ehv_bc_console_init);
339 
340 /******************************** TTY DRIVER ********************************/
341 
342 /*
343  * byte channel receive interrupt handler
344  *
345  * This ISR is called whenever data is available on a byte channel.
346  */
ehv_bc_tty_rx_isr(int irq,void * data)347 static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
348 {
349 	struct ehv_bc_data *bc = data;
350 	unsigned int rx_count, tx_count, len;
351 	int count;
352 	char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
353 	int ret;
354 
355 	/* Find out how much data needs to be read, and then ask the TTY layer
356 	 * if it can handle that much.  We want to ensure that every byte we
357 	 * read from the byte channel will be accepted by the TTY layer.
358 	 */
359 	ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
360 	count = tty_buffer_request_room(&bc->port, rx_count);
361 
362 	/* 'count' is the maximum amount of data the TTY layer can accept at
363 	 * this time.  However, during testing, I was never able to get 'count'
364 	 * to be less than 'rx_count'.  I'm not sure whether I'm calling it
365 	 * correctly.
366 	 */
367 
368 	while (count > 0) {
369 		len = min_t(unsigned int, count, sizeof(buffer));
370 
371 		/* Read some data from the byte channel.  This function will
372 		 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
373 		 */
374 		ev_byte_channel_receive(bc->handle, &len, buffer);
375 
376 		/* 'len' is now the amount of data that's been received. 'len'
377 		 * can't be zero, and most likely it's equal to one.
378 		 */
379 
380 		/* Pass the received data to the tty layer. */
381 		ret = tty_insert_flip_string(&bc->port, buffer, len);
382 
383 		/* 'ret' is the number of bytes that the TTY layer accepted.
384 		 * If it's not equal to 'len', then it means the buffer is
385 		 * full, which should never happen.  If it does happen, we can
386 		 * exit gracefully, but we drop the last 'len - ret' characters
387 		 * that we read from the byte channel.
388 		 */
389 		if (ret != len)
390 			break;
391 
392 		count -= len;
393 	}
394 
395 	/* Tell the tty layer that we're done. */
396 	tty_flip_buffer_push(&bc->port);
397 
398 	return IRQ_HANDLED;
399 }
400 
401 /*
402  * dequeue the transmit buffer to the hypervisor
403  *
404  * This function, which can be called in interrupt context, dequeues as much
405  * data as possible from the transmit buffer to the byte channel.
406  */
ehv_bc_tx_dequeue(struct ehv_bc_data * bc)407 static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
408 {
409 	unsigned int count;
410 	unsigned int len, ret;
411 	unsigned long flags;
412 
413 	do {
414 		spin_lock_irqsave(&bc->lock, flags);
415 		len = min_t(unsigned int,
416 			    CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
417 			    EV_BYTE_CHANNEL_MAX_BYTES);
418 
419 		ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
420 
421 		/* 'len' is valid only if the return code is 0 or EV_EAGAIN */
422 		if (!ret || (ret == EV_EAGAIN))
423 			bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
424 
425 		count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
426 		spin_unlock_irqrestore(&bc->lock, flags);
427 	} while (count && !ret);
428 
429 	spin_lock_irqsave(&bc->lock, flags);
430 	if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
431 		/*
432 		 * If we haven't emptied the buffer, then enable the TX IRQ.
433 		 * We'll get an interrupt when there's more room in the
434 		 * hypervisor's output buffer.
435 		 */
436 		enable_tx_interrupt(bc);
437 	else
438 		disable_tx_interrupt(bc);
439 	spin_unlock_irqrestore(&bc->lock, flags);
440 }
441 
442 /*
443  * byte channel transmit interrupt handler
444  *
445  * This ISR is called whenever space becomes available for transmitting
446  * characters on a byte channel.
447  */
ehv_bc_tty_tx_isr(int irq,void * data)448 static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
449 {
450 	struct ehv_bc_data *bc = data;
451 
452 	ehv_bc_tx_dequeue(bc);
453 	tty_port_tty_wakeup(&bc->port);
454 
455 	return IRQ_HANDLED;
456 }
457 
458 /*
459  * This function is called when the tty layer has data for us send.  We store
460  * the data first in a circular buffer, and then dequeue as much of that data
461  * as possible.
462  *
463  * We don't need to worry about whether there is enough room in the buffer for
464  * all the data.  The purpose of ehv_bc_tty_write_room() is to tell the tty
465  * layer how much data it can safely send to us.  We guarantee that
466  * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
467  * too much data.
468  */
ehv_bc_tty_write(struct tty_struct * ttys,const u8 * s,size_t count)469 static ssize_t ehv_bc_tty_write(struct tty_struct *ttys, const u8 *s,
470 				size_t count)
471 {
472 	struct ehv_bc_data *bc = ttys->driver_data;
473 	unsigned long flags;
474 	unsigned int len;
475 	unsigned int written = 0;
476 
477 	while (1) {
478 		spin_lock_irqsave(&bc->lock, flags);
479 		len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
480 		if (count < len)
481 			len = count;
482 		if (len) {
483 			memcpy(bc->buf + bc->head, s, len);
484 			bc->head = (bc->head + len) & (BUF_SIZE - 1);
485 		}
486 		spin_unlock_irqrestore(&bc->lock, flags);
487 		if (!len)
488 			break;
489 
490 		s += len;
491 		count -= len;
492 		written += len;
493 	}
494 
495 	ehv_bc_tx_dequeue(bc);
496 
497 	return written;
498 }
499 
500 /*
501  * This function can be called multiple times for a given tty_struct, which is
502  * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
503  *
504  * The tty layer will still call this function even if the device was not
505  * registered (i.e. tty_register_device() was not called).  This happens
506  * because tty_register_device() is optional and some legacy drivers don't
507  * use it.  So we need to check for that.
508  */
ehv_bc_tty_open(struct tty_struct * ttys,struct file * filp)509 static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
510 {
511 	struct ehv_bc_data *bc = &bcs[ttys->index];
512 
513 	if (!bc->dev)
514 		return -ENODEV;
515 
516 	return tty_port_open(&bc->port, ttys, filp);
517 }
518 
519 /*
520  * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
521  * still call this function to close the tty device.  So we can't assume that
522  * the tty port has been initialized.
523  */
ehv_bc_tty_close(struct tty_struct * ttys,struct file * filp)524 static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
525 {
526 	struct ehv_bc_data *bc = &bcs[ttys->index];
527 
528 	if (bc->dev)
529 		tty_port_close(&bc->port, ttys, filp);
530 }
531 
532 /*
533  * Return the amount of space in the output buffer
534  *
535  * This is actually a contract between the driver and the tty layer outlining
536  * how much write room the driver can guarantee will be sent OR BUFFERED.  This
537  * driver MUST honor the return value.
538  */
ehv_bc_tty_write_room(struct tty_struct * ttys)539 static unsigned int ehv_bc_tty_write_room(struct tty_struct *ttys)
540 {
541 	struct ehv_bc_data *bc = ttys->driver_data;
542 	unsigned long flags;
543 	unsigned int count;
544 
545 	spin_lock_irqsave(&bc->lock, flags);
546 	count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
547 	spin_unlock_irqrestore(&bc->lock, flags);
548 
549 	return count;
550 }
551 
552 /*
553  * Stop sending data to the tty layer
554  *
555  * This function is called when the tty layer's input buffers are getting full,
556  * so the driver should stop sending it data.  The easiest way to do this is to
557  * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
558  * called.
559  *
560  * The hypervisor will continue to queue up any incoming data.  If there is any
561  * data in the queue when the RX interrupt is enabled, we'll immediately get an
562  * RX interrupt.
563  */
ehv_bc_tty_throttle(struct tty_struct * ttys)564 static void ehv_bc_tty_throttle(struct tty_struct *ttys)
565 {
566 	struct ehv_bc_data *bc = ttys->driver_data;
567 
568 	disable_irq(bc->rx_irq);
569 }
570 
571 /*
572  * Resume sending data to the tty layer
573  *
574  * This function is called after previously calling ehv_bc_tty_throttle().  The
575  * tty layer's input buffers now have more room, so the driver can resume
576  * sending it data.
577  */
ehv_bc_tty_unthrottle(struct tty_struct * ttys)578 static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
579 {
580 	struct ehv_bc_data *bc = ttys->driver_data;
581 
582 	/* If there is any data in the queue when the RX interrupt is enabled,
583 	 * we'll immediately get an RX interrupt.
584 	 */
585 	enable_irq(bc->rx_irq);
586 }
587 
ehv_bc_tty_hangup(struct tty_struct * ttys)588 static void ehv_bc_tty_hangup(struct tty_struct *ttys)
589 {
590 	struct ehv_bc_data *bc = ttys->driver_data;
591 
592 	ehv_bc_tx_dequeue(bc);
593 	tty_port_hangup(&bc->port);
594 }
595 
596 /*
597  * TTY driver operations
598  *
599  * If we could ask the hypervisor how much data is still in the TX buffer, or
600  * at least how big the TX buffers are, then we could implement the
601  * .wait_until_sent and .chars_in_buffer functions.
602  */
603 static const struct tty_operations ehv_bc_ops = {
604 	.open		= ehv_bc_tty_open,
605 	.close		= ehv_bc_tty_close,
606 	.write		= ehv_bc_tty_write,
607 	.write_room	= ehv_bc_tty_write_room,
608 	.throttle	= ehv_bc_tty_throttle,
609 	.unthrottle	= ehv_bc_tty_unthrottle,
610 	.hangup		= ehv_bc_tty_hangup,
611 };
612 
613 /*
614  * initialize the TTY port
615  *
616  * This function will only be called once, no matter how many times
617  * ehv_bc_tty_open() is called.  That's why we register the ISR here, and also
618  * why we initialize tty_struct-related variables here.
619  */
ehv_bc_tty_port_activate(struct tty_port * port,struct tty_struct * ttys)620 static int ehv_bc_tty_port_activate(struct tty_port *port,
621 				    struct tty_struct *ttys)
622 {
623 	struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
624 	int ret;
625 
626 	ttys->driver_data = bc;
627 
628 	ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
629 	if (ret < 0) {
630 		dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
631 		       bc->rx_irq, ret);
632 		return ret;
633 	}
634 
635 	/* request_irq also enables the IRQ */
636 	bc->tx_irq_enabled = 1;
637 
638 	ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
639 	if (ret < 0) {
640 		dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
641 		       bc->tx_irq, ret);
642 		free_irq(bc->rx_irq, bc);
643 		return ret;
644 	}
645 
646 	/* The TX IRQ is enabled only when we can't write all the data to the
647 	 * byte channel at once, so by default it's disabled.
648 	 */
649 	disable_tx_interrupt(bc);
650 
651 	return 0;
652 }
653 
ehv_bc_tty_port_shutdown(struct tty_port * port)654 static void ehv_bc_tty_port_shutdown(struct tty_port *port)
655 {
656 	struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
657 
658 	free_irq(bc->tx_irq, bc);
659 	free_irq(bc->rx_irq, bc);
660 }
661 
662 static const struct tty_port_operations ehv_bc_tty_port_ops = {
663 	.activate = ehv_bc_tty_port_activate,
664 	.shutdown = ehv_bc_tty_port_shutdown,
665 };
666 
ehv_bc_tty_probe(struct platform_device * pdev)667 static int ehv_bc_tty_probe(struct platform_device *pdev)
668 {
669 	struct device_node *np = pdev->dev.of_node;
670 	struct ehv_bc_data *bc;
671 	const uint32_t *iprop;
672 	unsigned int handle;
673 	int ret;
674 	static unsigned int index = 1;
675 	unsigned int i;
676 
677 	iprop = of_get_property(np, "hv-handle", NULL);
678 	if (!iprop) {
679 		dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n",
680 			np);
681 		return -ENODEV;
682 	}
683 
684 	/* We already told the console layer that the index for the console
685 	 * device is zero, so we need to make sure that we use that index when
686 	 * we probe the console byte channel node.
687 	 */
688 	handle = be32_to_cpu(*iprop);
689 	i = (handle == stdout_bc) ? 0 : index++;
690 	bc = &bcs[i];
691 
692 	bc->handle = handle;
693 	bc->head = 0;
694 	bc->tail = 0;
695 	spin_lock_init(&bc->lock);
696 
697 	bc->rx_irq = irq_of_parse_and_map(np, 0);
698 	bc->tx_irq = irq_of_parse_and_map(np, 1);
699 	if (!bc->rx_irq || !bc->tx_irq) {
700 		dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n",
701 			np);
702 		ret = -ENODEV;
703 		goto error;
704 	}
705 
706 	tty_port_init(&bc->port);
707 	bc->port.ops = &ehv_bc_tty_port_ops;
708 
709 	bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
710 			&pdev->dev);
711 	if (IS_ERR(bc->dev)) {
712 		ret = PTR_ERR(bc->dev);
713 		dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
714 		goto error;
715 	}
716 
717 	dev_set_drvdata(&pdev->dev, bc);
718 
719 	dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
720 		ehv_bc_driver->name, i, bc->handle);
721 
722 	return 0;
723 
724 error:
725 	tty_port_destroy(&bc->port);
726 	irq_dispose_mapping(bc->tx_irq);
727 	irq_dispose_mapping(bc->rx_irq);
728 
729 	memset(bc, 0, sizeof(struct ehv_bc_data));
730 	return ret;
731 }
732 
733 static const struct of_device_id ehv_bc_tty_of_ids[] = {
734 	{ .compatible = "epapr,hv-byte-channel" },
735 	{}
736 };
737 
738 static struct platform_driver ehv_bc_tty_driver = {
739 	.driver = {
740 		.name = "ehv-bc",
741 		.of_match_table = ehv_bc_tty_of_ids,
742 		.suppress_bind_attrs = true,
743 	},
744 	.probe		= ehv_bc_tty_probe,
745 };
746 
747 /**
748  * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
749  *
750  * This function is called when this driver is loaded.
751  */
ehv_bc_init(void)752 static int __init ehv_bc_init(void)
753 {
754 	struct tty_driver *driver;
755 	struct device_node *np;
756 	unsigned int count = 0; /* Number of elements in bcs[] */
757 	int ret;
758 
759 	pr_info("ePAPR hypervisor byte channel driver\n");
760 
761 	/* Count the number of byte channels */
762 	for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
763 		count++;
764 
765 	if (!count)
766 		return -ENODEV;
767 
768 	/* The array index of an element in bcs[] is the same as the tty index
769 	 * for that element.  If you know the address of an element in the
770 	 * array, then you can use pointer math (e.g. "bc - bcs") to get its
771 	 * tty index.
772 	 */
773 	bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL);
774 	if (!bcs)
775 		return -ENOMEM;
776 
777 	driver = tty_alloc_driver(count, TTY_DRIVER_REAL_RAW |
778 			TTY_DRIVER_DYNAMIC_DEV);
779 	if (IS_ERR(driver)) {
780 		ret = PTR_ERR(driver);
781 		goto err_free_bcs;
782 	}
783 
784 	driver->driver_name = "ehv-bc";
785 	driver->name = ehv_bc_console.name;
786 	driver->type = TTY_DRIVER_TYPE_CONSOLE;
787 	driver->subtype = SYSTEM_TYPE_CONSOLE;
788 	driver->init_termios = tty_std_termios;
789 	tty_set_operations(driver, &ehv_bc_ops);
790 
791 	ret = tty_register_driver(driver);
792 	if (ret) {
793 		pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
794 		goto err_tty_driver_kref_put;
795 	}
796 
797 	ehv_bc_driver = driver;
798 
799 	ret = platform_driver_register(&ehv_bc_tty_driver);
800 	if (ret) {
801 		pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
802 		       ret);
803 		goto err_deregister_tty_driver;
804 	}
805 
806 	return 0;
807 
808 err_deregister_tty_driver:
809 	ehv_bc_driver = NULL;
810 	tty_unregister_driver(driver);
811 err_tty_driver_kref_put:
812 	tty_driver_kref_put(driver);
813 err_free_bcs:
814 	kfree(bcs);
815 
816 	return ret;
817 }
818 device_initcall(ehv_bc_init);
819