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 | u8 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 | */ |
86 | static void enable_tx_interrupt(struct ehv_bc_data *bc) |
87 | { |
88 | if (!bc->tx_irq_enabled) { |
89 | enable_irq(irq: bc->tx_irq); |
90 | bc->tx_irq_enabled = 1; |
91 | } |
92 | } |
93 | |
94 | static void disable_tx_interrupt(struct ehv_bc_data *bc) |
95 | { |
96 | if (bc->tx_irq_enabled) { |
97 | disable_irq_nosync(irq: 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 | */ |
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(device: np, "epapr,hv-byte-channel" )) |
118 | return 0; |
119 | |
120 | stdout_irq = irq_of_parse_and_map(node: np, index: 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(node: np, name: "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 | |
139 | static unsigned int local_ev_byte_channel_send(unsigned int handle, |
140 | unsigned int *count, |
141 | const u8 *p) |
142 | { |
143 | u8 buffer[EV_BYTE_CHANNEL_MAX_BYTES]; |
144 | unsigned int c = *count; |
145 | |
146 | /* |
147 | * ev_byte_channel_send() expects at least EV_BYTE_CHANNEL_MAX_BYTES |
148 | * (16 B) in the buffer. Fake it using a local buffer if needed. |
149 | */ |
150 | if (c < sizeof(buffer)) { |
151 | memcpy_and_pad(dest: buffer, dest_len: sizeof(buffer), src: p, count: c, pad: 0); |
152 | p = buffer; |
153 | } |
154 | return ev_byte_channel_send(handle, count, p); |
155 | } |
156 | |
157 | /*************************** EARLY CONSOLE DRIVER ***************************/ |
158 | |
159 | #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC |
160 | |
161 | /* |
162 | * send a byte to a byte channel, wait if necessary |
163 | * |
164 | * This function sends a byte to a byte channel, and it waits and |
165 | * retries if the byte channel is full. It returns if the character |
166 | * has been sent, or if some error has occurred. |
167 | * |
168 | */ |
169 | static void byte_channel_spin_send(const u8 data) |
170 | { |
171 | int ret, count; |
172 | |
173 | do { |
174 | count = 1; |
175 | ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, |
176 | &count, &data); |
177 | } while (ret == EV_EAGAIN); |
178 | } |
179 | |
180 | /* |
181 | * The udbg subsystem calls this function to display a single character. |
182 | * We convert CR to a CR/LF. |
183 | */ |
184 | static void ehv_bc_udbg_putc(char c) |
185 | { |
186 | if (c == '\n') |
187 | byte_channel_spin_send('\r'); |
188 | |
189 | byte_channel_spin_send(c); |
190 | } |
191 | |
192 | /* |
193 | * early console initialization |
194 | * |
195 | * PowerPC kernels support an early printk console, also known as udbg. |
196 | * This function must be called via the ppc_md.init_early function pointer. |
197 | * At this point, the device tree has been unflattened, so we can obtain the |
198 | * byte channel handle for stdout. |
199 | * |
200 | * We only support displaying of characters (putc). We do not support |
201 | * keyboard input. |
202 | */ |
203 | void __init udbg_init_ehv_bc(void) |
204 | { |
205 | unsigned int rx_count, tx_count; |
206 | unsigned int ret; |
207 | |
208 | /* Verify the byte channel handle */ |
209 | ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, |
210 | &rx_count, &tx_count); |
211 | if (ret) |
212 | return; |
213 | |
214 | udbg_putc = ehv_bc_udbg_putc; |
215 | register_early_udbg_console(); |
216 | |
217 | udbg_printf("ehv-bc: early console using byte channel handle %u\n" , |
218 | CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); |
219 | } |
220 | |
221 | #endif |
222 | |
223 | /****************************** CONSOLE DRIVER ******************************/ |
224 | |
225 | static struct tty_driver *ehv_bc_driver; |
226 | |
227 | /* |
228 | * Byte channel console sending worker function. |
229 | * |
230 | * For consoles, if the output buffer is full, we should just spin until it |
231 | * clears. |
232 | */ |
233 | static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s, |
234 | unsigned int count) |
235 | { |
236 | unsigned int len; |
237 | int ret = 0; |
238 | |
239 | while (count) { |
240 | len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES); |
241 | do { |
242 | ret = local_ev_byte_channel_send(handle, &len, s); |
243 | } while (ret == EV_EAGAIN); |
244 | count -= len; |
245 | s += len; |
246 | } |
247 | |
248 | return ret; |
249 | } |
250 | |
251 | /* |
252 | * write a string to the console |
253 | * |
254 | * This function gets called to write a string from the kernel, typically from |
255 | * a printk(). This function spins until all data is written. |
256 | * |
257 | * We copy the data to a temporary buffer because we need to insert a \r in |
258 | * front of every \n. It's more efficient to copy the data to the buffer than |
259 | * it is to make multiple hcalls for each character or each newline. |
260 | */ |
261 | static void ehv_bc_console_write(struct console *co, const char *s, |
262 | unsigned int count) |
263 | { |
264 | char s2[EV_BYTE_CHANNEL_MAX_BYTES]; |
265 | unsigned int i, j = 0; |
266 | char c; |
267 | |
268 | for (i = 0; i < count; i++) { |
269 | c = *s++; |
270 | |
271 | if (c == '\n') |
272 | s2[j++] = '\r'; |
273 | |
274 | s2[j++] = c; |
275 | if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) { |
276 | if (ehv_bc_console_byte_channel_send(handle: stdout_bc, s: s2, count: j)) |
277 | return; |
278 | j = 0; |
279 | } |
280 | } |
281 | |
282 | if (j) |
283 | ehv_bc_console_byte_channel_send(handle: stdout_bc, s: s2, count: j); |
284 | } |
285 | |
286 | /* |
287 | * When /dev/console is opened, the kernel iterates the console list looking |
288 | * for one with ->device and then calls that method. On success, it expects |
289 | * the passed-in int* to contain the minor number to use. |
290 | */ |
291 | static struct tty_driver *ehv_bc_console_device(struct console *co, int *index) |
292 | { |
293 | *index = co->index; |
294 | |
295 | return ehv_bc_driver; |
296 | } |
297 | |
298 | static struct console ehv_bc_console = { |
299 | .name = "ttyEHV" , |
300 | .write = ehv_bc_console_write, |
301 | .device = ehv_bc_console_device, |
302 | .flags = CON_PRINTBUFFER | CON_ENABLED, |
303 | }; |
304 | |
305 | /* |
306 | * Console initialization |
307 | * |
308 | * This is the first function that is called after the device tree is |
309 | * available, so here is where we determine the byte channel handle and IRQ for |
310 | * stdout/stdin, even though that information is used by the tty and character |
311 | * drivers. |
312 | */ |
313 | static int __init ehv_bc_console_init(void) |
314 | { |
315 | if (!find_console_handle()) { |
316 | pr_debug("ehv-bc: stdout is not a byte channel\n" ); |
317 | return -ENODEV; |
318 | } |
319 | |
320 | #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC |
321 | /* Print a friendly warning if the user chose the wrong byte channel |
322 | * handle for udbg. |
323 | */ |
324 | if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE) |
325 | pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n" , |
326 | CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); |
327 | #endif |
328 | |
329 | /* add_preferred_console() must be called before register_console(), |
330 | otherwise it won't work. However, we don't want to enumerate all the |
331 | byte channels here, either, since we only care about one. */ |
332 | |
333 | add_preferred_console(name: ehv_bc_console.name, idx: ehv_bc_console.index, NULL); |
334 | register_console(&ehv_bc_console); |
335 | |
336 | pr_info("ehv-bc: registered console driver for byte channel %u\n" , |
337 | stdout_bc); |
338 | |
339 | return 0; |
340 | } |
341 | console_initcall(ehv_bc_console_init); |
342 | |
343 | /******************************** TTY DRIVER ********************************/ |
344 | |
345 | /* |
346 | * byte channel receive interrupt handler |
347 | * |
348 | * This ISR is called whenever data is available on a byte channel. |
349 | */ |
350 | static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data) |
351 | { |
352 | struct ehv_bc_data *bc = data; |
353 | unsigned int rx_count, tx_count, len; |
354 | int count; |
355 | char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; |
356 | int ret; |
357 | |
358 | /* Find out how much data needs to be read, and then ask the TTY layer |
359 | * if it can handle that much. We want to ensure that every byte we |
360 | * read from the byte channel will be accepted by the TTY layer. |
361 | */ |
362 | ev_byte_channel_poll(bc->handle, &rx_count, &tx_count); |
363 | count = tty_buffer_request_room(port: &bc->port, size: rx_count); |
364 | |
365 | /* 'count' is the maximum amount of data the TTY layer can accept at |
366 | * this time. However, during testing, I was never able to get 'count' |
367 | * to be less than 'rx_count'. I'm not sure whether I'm calling it |
368 | * correctly. |
369 | */ |
370 | |
371 | while (count > 0) { |
372 | len = min_t(unsigned int, count, sizeof(buffer)); |
373 | |
374 | /* Read some data from the byte channel. This function will |
375 | * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes. |
376 | */ |
377 | ev_byte_channel_receive(bc->handle, &len, buffer); |
378 | |
379 | /* 'len' is now the amount of data that's been received. 'len' |
380 | * can't be zero, and most likely it's equal to one. |
381 | */ |
382 | |
383 | /* Pass the received data to the tty layer. */ |
384 | ret = tty_insert_flip_string(port: &bc->port, chars: buffer, size: len); |
385 | |
386 | /* 'ret' is the number of bytes that the TTY layer accepted. |
387 | * If it's not equal to 'len', then it means the buffer is |
388 | * full, which should never happen. If it does happen, we can |
389 | * exit gracefully, but we drop the last 'len - ret' characters |
390 | * that we read from the byte channel. |
391 | */ |
392 | if (ret != len) |
393 | break; |
394 | |
395 | count -= len; |
396 | } |
397 | |
398 | /* Tell the tty layer that we're done. */ |
399 | tty_flip_buffer_push(port: &bc->port); |
400 | |
401 | return IRQ_HANDLED; |
402 | } |
403 | |
404 | /* |
405 | * dequeue the transmit buffer to the hypervisor |
406 | * |
407 | * This function, which can be called in interrupt context, dequeues as much |
408 | * data as possible from the transmit buffer to the byte channel. |
409 | */ |
410 | static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc) |
411 | { |
412 | unsigned int count; |
413 | unsigned int len, ret; |
414 | unsigned long flags; |
415 | |
416 | do { |
417 | spin_lock_irqsave(&bc->lock, flags); |
418 | len = min_t(unsigned int, |
419 | CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE), |
420 | EV_BYTE_CHANNEL_MAX_BYTES); |
421 | |
422 | ret = local_ev_byte_channel_send(handle: bc->handle, count: &len, p: bc->buf + bc->tail); |
423 | |
424 | /* 'len' is valid only if the return code is 0 or EV_EAGAIN */ |
425 | if (!ret || (ret == EV_EAGAIN)) |
426 | bc->tail = (bc->tail + len) & (BUF_SIZE - 1); |
427 | |
428 | count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE); |
429 | spin_unlock_irqrestore(lock: &bc->lock, flags); |
430 | } while (count && !ret); |
431 | |
432 | spin_lock_irqsave(&bc->lock, flags); |
433 | if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE)) |
434 | /* |
435 | * If we haven't emptied the buffer, then enable the TX IRQ. |
436 | * We'll get an interrupt when there's more room in the |
437 | * hypervisor's output buffer. |
438 | */ |
439 | enable_tx_interrupt(bc); |
440 | else |
441 | disable_tx_interrupt(bc); |
442 | spin_unlock_irqrestore(lock: &bc->lock, flags); |
443 | } |
444 | |
445 | /* |
446 | * byte channel transmit interrupt handler |
447 | * |
448 | * This ISR is called whenever space becomes available for transmitting |
449 | * characters on a byte channel. |
450 | */ |
451 | static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data) |
452 | { |
453 | struct ehv_bc_data *bc = data; |
454 | |
455 | ehv_bc_tx_dequeue(bc); |
456 | tty_port_tty_wakeup(port: &bc->port); |
457 | |
458 | return IRQ_HANDLED; |
459 | } |
460 | |
461 | /* |
462 | * This function is called when the tty layer has data for us send. We store |
463 | * the data first in a circular buffer, and then dequeue as much of that data |
464 | * as possible. |
465 | * |
466 | * We don't need to worry about whether there is enough room in the buffer for |
467 | * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty |
468 | * layer how much data it can safely send to us. We guarantee that |
469 | * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us |
470 | * too much data. |
471 | */ |
472 | static ssize_t ehv_bc_tty_write(struct tty_struct *ttys, const u8 *s, |
473 | size_t count) |
474 | { |
475 | struct ehv_bc_data *bc = ttys->driver_data; |
476 | unsigned long flags; |
477 | size_t len, written = 0; |
478 | |
479 | while (1) { |
480 | spin_lock_irqsave(&bc->lock, flags); |
481 | len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE); |
482 | if (count < len) |
483 | len = count; |
484 | if (len) { |
485 | memcpy(bc->buf + bc->head, s, len); |
486 | bc->head = (bc->head + len) & (BUF_SIZE - 1); |
487 | } |
488 | spin_unlock_irqrestore(lock: &bc->lock, flags); |
489 | if (!len) |
490 | break; |
491 | |
492 | s += len; |
493 | count -= len; |
494 | written += len; |
495 | } |
496 | |
497 | ehv_bc_tx_dequeue(bc); |
498 | |
499 | return written; |
500 | } |
501 | |
502 | /* |
503 | * This function can be called multiple times for a given tty_struct, which is |
504 | * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead. |
505 | * |
506 | * The tty layer will still call this function even if the device was not |
507 | * registered (i.e. tty_register_device() was not called). This happens |
508 | * because tty_register_device() is optional and some legacy drivers don't |
509 | * use it. So we need to check for that. |
510 | */ |
511 | static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp) |
512 | { |
513 | struct ehv_bc_data *bc = &bcs[ttys->index]; |
514 | |
515 | if (!bc->dev) |
516 | return -ENODEV; |
517 | |
518 | return tty_port_open(port: &bc->port, tty: ttys, filp); |
519 | } |
520 | |
521 | /* |
522 | * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will |
523 | * still call this function to close the tty device. So we can't assume that |
524 | * the tty port has been initialized. |
525 | */ |
526 | static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp) |
527 | { |
528 | struct ehv_bc_data *bc = &bcs[ttys->index]; |
529 | |
530 | if (bc->dev) |
531 | tty_port_close(port: &bc->port, tty: ttys, filp); |
532 | } |
533 | |
534 | /* |
535 | * Return the amount of space in the output buffer |
536 | * |
537 | * This is actually a contract between the driver and the tty layer outlining |
538 | * how much write room the driver can guarantee will be sent OR BUFFERED. This |
539 | * driver MUST honor the return value. |
540 | */ |
541 | static unsigned int ehv_bc_tty_write_room(struct tty_struct *ttys) |
542 | { |
543 | struct ehv_bc_data *bc = ttys->driver_data; |
544 | unsigned long flags; |
545 | unsigned int count; |
546 | |
547 | spin_lock_irqsave(&bc->lock, flags); |
548 | count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE); |
549 | spin_unlock_irqrestore(lock: &bc->lock, flags); |
550 | |
551 | return count; |
552 | } |
553 | |
554 | /* |
555 | * Stop sending data to the tty layer |
556 | * |
557 | * This function is called when the tty layer's input buffers are getting full, |
558 | * so the driver should stop sending it data. The easiest way to do this is to |
559 | * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being |
560 | * called. |
561 | * |
562 | * The hypervisor will continue to queue up any incoming data. If there is any |
563 | * data in the queue when the RX interrupt is enabled, we'll immediately get an |
564 | * RX interrupt. |
565 | */ |
566 | static void ehv_bc_tty_throttle(struct tty_struct *ttys) |
567 | { |
568 | struct ehv_bc_data *bc = ttys->driver_data; |
569 | |
570 | disable_irq(irq: bc->rx_irq); |
571 | } |
572 | |
573 | /* |
574 | * Resume sending data to the tty layer |
575 | * |
576 | * This function is called after previously calling ehv_bc_tty_throttle(). The |
577 | * tty layer's input buffers now have more room, so the driver can resume |
578 | * sending it data. |
579 | */ |
580 | static void ehv_bc_tty_unthrottle(struct tty_struct *ttys) |
581 | { |
582 | struct ehv_bc_data *bc = ttys->driver_data; |
583 | |
584 | /* If there is any data in the queue when the RX interrupt is enabled, |
585 | * we'll immediately get an RX interrupt. |
586 | */ |
587 | enable_irq(irq: bc->rx_irq); |
588 | } |
589 | |
590 | static void ehv_bc_tty_hangup(struct tty_struct *ttys) |
591 | { |
592 | struct ehv_bc_data *bc = ttys->driver_data; |
593 | |
594 | ehv_bc_tx_dequeue(bc); |
595 | tty_port_hangup(port: &bc->port); |
596 | } |
597 | |
598 | /* |
599 | * TTY driver operations |
600 | * |
601 | * If we could ask the hypervisor how much data is still in the TX buffer, or |
602 | * at least how big the TX buffers are, then we could implement the |
603 | * .wait_until_sent and .chars_in_buffer functions. |
604 | */ |
605 | static const struct tty_operations ehv_bc_ops = { |
606 | .open = ehv_bc_tty_open, |
607 | .close = ehv_bc_tty_close, |
608 | .write = ehv_bc_tty_write, |
609 | .write_room = ehv_bc_tty_write_room, |
610 | .throttle = ehv_bc_tty_throttle, |
611 | .unthrottle = ehv_bc_tty_unthrottle, |
612 | .hangup = ehv_bc_tty_hangup, |
613 | }; |
614 | |
615 | /* |
616 | * initialize the TTY port |
617 | * |
618 | * This function will only be called once, no matter how many times |
619 | * ehv_bc_tty_open() is called. That's why we register the ISR here, and also |
620 | * why we initialize tty_struct-related variables here. |
621 | */ |
622 | static int ehv_bc_tty_port_activate(struct tty_port *port, |
623 | struct tty_struct *ttys) |
624 | { |
625 | struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); |
626 | int ret; |
627 | |
628 | ttys->driver_data = bc; |
629 | |
630 | ret = request_irq(irq: bc->rx_irq, handler: ehv_bc_tty_rx_isr, flags: 0, name: "ehv-bc" , dev: bc); |
631 | if (ret < 0) { |
632 | dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n" , |
633 | bc->rx_irq, ret); |
634 | return ret; |
635 | } |
636 | |
637 | /* request_irq also enables the IRQ */ |
638 | bc->tx_irq_enabled = 1; |
639 | |
640 | ret = request_irq(irq: bc->tx_irq, handler: ehv_bc_tty_tx_isr, flags: 0, name: "ehv-bc" , dev: bc); |
641 | if (ret < 0) { |
642 | dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n" , |
643 | bc->tx_irq, ret); |
644 | free_irq(bc->rx_irq, bc); |
645 | return ret; |
646 | } |
647 | |
648 | /* The TX IRQ is enabled only when we can't write all the data to the |
649 | * byte channel at once, so by default it's disabled. |
650 | */ |
651 | disable_tx_interrupt(bc); |
652 | |
653 | return 0; |
654 | } |
655 | |
656 | static void ehv_bc_tty_port_shutdown(struct tty_port *port) |
657 | { |
658 | struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); |
659 | |
660 | free_irq(bc->tx_irq, bc); |
661 | free_irq(bc->rx_irq, bc); |
662 | } |
663 | |
664 | static const struct tty_port_operations ehv_bc_tty_port_ops = { |
665 | .activate = ehv_bc_tty_port_activate, |
666 | .shutdown = ehv_bc_tty_port_shutdown, |
667 | }; |
668 | |
669 | static int ehv_bc_tty_probe(struct platform_device *pdev) |
670 | { |
671 | struct device_node *np = pdev->dev.of_node; |
672 | struct ehv_bc_data *bc; |
673 | const uint32_t *iprop; |
674 | unsigned int handle; |
675 | int ret; |
676 | static unsigned int index = 1; |
677 | unsigned int i; |
678 | |
679 | iprop = of_get_property(node: np, name: "hv-handle" , NULL); |
680 | if (!iprop) { |
681 | dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n" , |
682 | np); |
683 | return -ENODEV; |
684 | } |
685 | |
686 | /* We already told the console layer that the index for the console |
687 | * device is zero, so we need to make sure that we use that index when |
688 | * we probe the console byte channel node. |
689 | */ |
690 | handle = be32_to_cpu(*iprop); |
691 | i = (handle == stdout_bc) ? 0 : index++; |
692 | bc = &bcs[i]; |
693 | |
694 | bc->handle = handle; |
695 | bc->head = 0; |
696 | bc->tail = 0; |
697 | spin_lock_init(&bc->lock); |
698 | |
699 | bc->rx_irq = irq_of_parse_and_map(node: np, index: 0); |
700 | bc->tx_irq = irq_of_parse_and_map(node: np, index: 1); |
701 | if (!bc->rx_irq || !bc->tx_irq) { |
702 | dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n" , |
703 | np); |
704 | ret = -ENODEV; |
705 | goto error; |
706 | } |
707 | |
708 | tty_port_init(port: &bc->port); |
709 | bc->port.ops = &ehv_bc_tty_port_ops; |
710 | |
711 | bc->dev = tty_port_register_device(port: &bc->port, driver: ehv_bc_driver, index: i, |
712 | device: &pdev->dev); |
713 | if (IS_ERR(ptr: bc->dev)) { |
714 | ret = PTR_ERR(ptr: bc->dev); |
715 | dev_err(&pdev->dev, "could not register tty (ret=%i)\n" , ret); |
716 | goto error; |
717 | } |
718 | |
719 | dev_set_drvdata(dev: &pdev->dev, data: bc); |
720 | |
721 | dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n" , |
722 | ehv_bc_driver->name, i, bc->handle); |
723 | |
724 | return 0; |
725 | |
726 | error: |
727 | tty_port_destroy(port: &bc->port); |
728 | irq_dispose_mapping(virq: bc->tx_irq); |
729 | irq_dispose_mapping(virq: bc->rx_irq); |
730 | |
731 | memset(bc, 0, sizeof(struct ehv_bc_data)); |
732 | return ret; |
733 | } |
734 | |
735 | static const struct of_device_id ehv_bc_tty_of_ids[] = { |
736 | { .compatible = "epapr,hv-byte-channel" }, |
737 | {} |
738 | }; |
739 | |
740 | static struct platform_driver ehv_bc_tty_driver = { |
741 | .driver = { |
742 | .name = "ehv-bc" , |
743 | .of_match_table = ehv_bc_tty_of_ids, |
744 | .suppress_bind_attrs = true, |
745 | }, |
746 | .probe = ehv_bc_tty_probe, |
747 | }; |
748 | |
749 | /** |
750 | * ehv_bc_init - ePAPR hypervisor byte channel driver initialization |
751 | * |
752 | * This function is called when this driver is loaded. |
753 | */ |
754 | static int __init ehv_bc_init(void) |
755 | { |
756 | struct tty_driver *driver; |
757 | struct device_node *np; |
758 | unsigned int count = 0; /* Number of elements in bcs[] */ |
759 | int ret; |
760 | |
761 | pr_info("ePAPR hypervisor byte channel driver\n" ); |
762 | |
763 | /* Count the number of byte channels */ |
764 | for_each_compatible_node(np, NULL, "epapr,hv-byte-channel" ) |
765 | count++; |
766 | |
767 | if (!count) |
768 | return -ENODEV; |
769 | |
770 | /* The array index of an element in bcs[] is the same as the tty index |
771 | * for that element. If you know the address of an element in the |
772 | * array, then you can use pointer math (e.g. "bc - bcs") to get its |
773 | * tty index. |
774 | */ |
775 | bcs = kcalloc(n: count, size: sizeof(struct ehv_bc_data), GFP_KERNEL); |
776 | if (!bcs) |
777 | return -ENOMEM; |
778 | |
779 | driver = tty_alloc_driver(count, TTY_DRIVER_REAL_RAW | |
780 | TTY_DRIVER_DYNAMIC_DEV); |
781 | if (IS_ERR(ptr: driver)) { |
782 | ret = PTR_ERR(ptr: driver); |
783 | goto err_free_bcs; |
784 | } |
785 | |
786 | driver->driver_name = "ehv-bc" ; |
787 | driver->name = ehv_bc_console.name; |
788 | driver->type = TTY_DRIVER_TYPE_CONSOLE; |
789 | driver->subtype = SYSTEM_TYPE_CONSOLE; |
790 | driver->init_termios = tty_std_termios; |
791 | tty_set_operations(driver, op: &ehv_bc_ops); |
792 | |
793 | ret = tty_register_driver(driver); |
794 | if (ret) { |
795 | pr_err("ehv-bc: could not register tty driver (ret=%i)\n" , ret); |
796 | goto err_tty_driver_kref_put; |
797 | } |
798 | |
799 | ehv_bc_driver = driver; |
800 | |
801 | ret = platform_driver_register(&ehv_bc_tty_driver); |
802 | if (ret) { |
803 | pr_err("ehv-bc: could not register platform driver (ret=%i)\n" , |
804 | ret); |
805 | goto err_deregister_tty_driver; |
806 | } |
807 | |
808 | return 0; |
809 | |
810 | err_deregister_tty_driver: |
811 | ehv_bc_driver = NULL; |
812 | tty_unregister_driver(driver); |
813 | err_tty_driver_kref_put: |
814 | tty_driver_kref_put(driver); |
815 | err_free_bcs: |
816 | kfree(objp: bcs); |
817 | |
818 | return ret; |
819 | } |
820 | device_initcall(ehv_bc_init); |
821 | |