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e3b3d0f5 | 1 | // SPDX-License-Identifier: GPL-2.0 |
dcd83aaf TT |
2 | /* ePAPR hypervisor byte channel device driver |
3 | * | |
4 | * Copyright 2009-2011 Freescale Semiconductor, Inc. | |
5 | * | |
6 | * Author: Timur Tabi <timur@freescale.com> | |
7 | * | |
dcd83aaf TT |
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 | ||
dcd83aaf TT |
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> | |
5af50730 | 31 | #include <linux/of_irq.h> |
dcd83aaf TT |
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 */ | |
0d08abb9 | 52 | u8 buf[BUF_SIZE]; /* transmit circular buffer */ |
dcd83aaf TT |
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(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(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. | |
dcd83aaf TT |
107 | */ |
108 | static int find_console_handle(void) | |
109 | { | |
a752ee56 | 110 | struct device_node *np = of_stdout; |
dcd83aaf TT |
111 | const uint32_t *iprop; |
112 | ||
dcd83aaf TT |
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 | |
a752ee56 | 115 | * indicates that it's a byte channel node. |
dcd83aaf | 116 | */ |
a752ee56 | 117 | if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel")) |
dcd83aaf | 118 | return 0; |
dcd83aaf TT |
119 | |
120 | stdout_irq = irq_of_parse_and_map(np, 0); | |
72da688b | 121 | if (!stdout_irq) { |
a73ee843 | 122 | pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np); |
dcd83aaf TT |
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) { | |
fff10721 RH |
131 | pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n", |
132 | np); | |
dcd83aaf TT |
133 | return 0; |
134 | } | |
135 | stdout_bc = be32_to_cpu(*iprop); | |
dcd83aaf TT |
136 | return 1; |
137 | } | |
138 | ||
3670664b SR |
139 | static unsigned int local_ev_byte_channel_send(unsigned int handle, |
140 | unsigned int *count, | |
0d08abb9 | 141 | const u8 *p) |
3670664b | 142 | { |
0d08abb9 | 143 | u8 buffer[EV_BYTE_CHANNEL_MAX_BYTES]; |
3670664b SR |
144 | unsigned int c = *count; |
145 | ||
9d3e3301 JSS |
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 | */ | |
3670664b | 150 | if (c < sizeof(buffer)) { |
9d3e3301 | 151 | memcpy_and_pad(buffer, sizeof(buffer), p, c, 0); |
3670664b SR |
152 | p = buffer; |
153 | } | |
154 | return ev_byte_channel_send(handle, count, p); | |
155 | } | |
156 | ||
dcd83aaf TT |
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 | */ | |
0d08abb9 | 169 | static void byte_channel_spin_send(const u8 data) |
dcd83aaf TT |
170 | { |
171 | int ret, count; | |
172 | ||
173 | do { | |
174 | count = 1; | |
3670664b | 175 | ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, |
dcd83aaf TT |
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 | ||
dcd83aaf TT |
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 { | |
3670664b | 242 | ret = local_ev_byte_channel_send(handle, &len, s); |
dcd83aaf TT |
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 | { | |
dcd83aaf TT |
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)) { | |
fd01a7a1 | 276 | if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j)) |
dcd83aaf TT |
277 | return; |
278 | j = 0; | |
279 | } | |
280 | } | |
281 | ||
282 | if (j) | |
fd01a7a1 | 283 | ehv_bc_console_byte_channel_send(stdout_bc, s2, j); |
dcd83aaf TT |
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) | |
e620e548 JP |
325 | pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n", |
326 | CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); | |
dcd83aaf TT |
327 | #endif |
328 | ||
dcd83aaf TT |
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(ehv_bc_console.name, 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 | /* | |
57f5d648 | 346 | * byte channel receive interrupt handler |
dcd83aaf TT |
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; | |
dcd83aaf TT |
353 | unsigned int rx_count, tx_count, len; |
354 | int count; | |
355 | char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; | |
356 | int ret; | |
357 | ||
dcd83aaf TT |
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); | |
227434f8 | 363 | count = tty_buffer_request_room(&bc->port, rx_count); |
dcd83aaf TT |
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. */ | |
05c7cd39 | 384 | ret = tty_insert_flip_string(&bc->port, buffer, len); |
dcd83aaf TT |
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. */ | |
2e124b4a | 399 | tty_flip_buffer_push(&bc->port); |
dcd83aaf TT |
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 | ||
3670664b | 422 | ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail); |
dcd83aaf TT |
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(&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(&bc->lock, flags); | |
443 | } | |
444 | ||
445 | /* | |
57f5d648 | 446 | * byte channel transmit interrupt handler |
dcd83aaf TT |
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; | |
dcd83aaf TT |
454 | |
455 | ehv_bc_tx_dequeue(bc); | |
6aad04f2 | 456 | tty_port_tty_wakeup(&bc->port); |
dcd83aaf TT |
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 | */ | |
95713967 JSS |
472 | static ssize_t ehv_bc_tty_write(struct tty_struct *ttys, const u8 *s, |
473 | size_t count) | |
dcd83aaf TT |
474 | { |
475 | struct ehv_bc_data *bc = ttys->driver_data; | |
476 | unsigned long flags; | |
0d08abb9 | 477 | size_t len, written = 0; |
dcd83aaf TT |
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(&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(&bc->port, 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(&bc->port, 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 | */ | |
03b3b1a2 | 541 | static unsigned int ehv_bc_tty_write_room(struct tty_struct *ttys) |
dcd83aaf TT |
542 | { |
543 | struct ehv_bc_data *bc = ttys->driver_data; | |
544 | unsigned long flags; | |
03b3b1a2 | 545 | unsigned int count; |
dcd83aaf TT |
546 | |
547 | spin_lock_irqsave(&bc->lock, flags); | |
548 | count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE); | |
549 | spin_unlock_irqrestore(&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(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(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(&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(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", 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(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", 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 | ||
9671f099 | 669 | static int ehv_bc_tty_probe(struct platform_device *pdev) |
dcd83aaf TT |
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(np, "hv-handle", NULL); | |
680 | if (!iprop) { | |
fff10721 RH |
681 | dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n", |
682 | np); | |
dcd83aaf TT |
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(np, 0); | |
700 | bc->tx_irq = irq_of_parse_and_map(np, 1); | |
72da688b | 701 | if (!bc->rx_irq || !bc->tx_irq) { |
fff10721 RH |
702 | dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n", |
703 | np); | |
dcd83aaf TT |
704 | ret = -ENODEV; |
705 | goto error; | |
706 | } | |
707 | ||
734cc178 JS |
708 | tty_port_init(&bc->port); |
709 | bc->port.ops = &ehv_bc_tty_port_ops; | |
710 | ||
711 | bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i, | |
712 | &pdev->dev); | |
dcd83aaf TT |
713 | if (IS_ERR(bc->dev)) { |
714 | ret = PTR_ERR(bc->dev); | |
715 | dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret); | |
716 | goto error; | |
717 | } | |
718 | ||
dcd83aaf TT |
719 | dev_set_drvdata(&pdev->dev, 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: | |
191c5f10 | 727 | tty_port_destroy(&bc->port); |
dcd83aaf TT |
728 | irq_dispose_mapping(bc->tx_irq); |
729 | irq_dispose_mapping(bc->rx_irq); | |
730 | ||
731 | memset(bc, 0, sizeof(struct ehv_bc_data)); | |
732 | return ret; | |
733 | } | |
734 | ||
dcd83aaf TT |
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 = { | |
dcd83aaf TT |
742 | .name = "ehv-bc", |
743 | .of_match_table = ehv_bc_tty_of_ids, | |
fc7f47bf | 744 | .suppress_bind_attrs = true, |
dcd83aaf TT |
745 | }, |
746 | .probe = ehv_bc_tty_probe, | |
dcd83aaf TT |
747 | }; |
748 | ||
749 | /** | |
750 | * ehv_bc_init - ePAPR hypervisor byte channel driver initialization | |
751 | * | |
fc7f47bf | 752 | * This function is called when this driver is loaded. |
dcd83aaf TT |
753 | */ |
754 | static int __init ehv_bc_init(void) | |
755 | { | |
0524513a | 756 | struct tty_driver *driver; |
dcd83aaf TT |
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 | */ | |
6396bb22 | 775 | bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL); |
dcd83aaf TT |
776 | if (!bcs) |
777 | return -ENOMEM; | |
778 | ||
39b7b42b JS |
779 | driver = tty_alloc_driver(count, TTY_DRIVER_REAL_RAW | |
780 | TTY_DRIVER_DYNAMIC_DEV); | |
781 | if (IS_ERR(driver)) { | |
782 | ret = PTR_ERR(driver); | |
11d4d321 | 783 | goto err_free_bcs; |
dcd83aaf TT |
784 | } |
785 | ||
0524513a JS |
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; | |
0524513a | 791 | tty_set_operations(driver, &ehv_bc_ops); |
dcd83aaf | 792 | |
0524513a | 793 | ret = tty_register_driver(driver); |
dcd83aaf TT |
794 | if (ret) { |
795 | pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret); | |
9f90a4dd | 796 | goto err_tty_driver_kref_put; |
dcd83aaf TT |
797 | } |
798 | ||
0524513a JS |
799 | ehv_bc_driver = driver; |
800 | ||
dcd83aaf TT |
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); | |
11d4d321 | 805 | goto err_deregister_tty_driver; |
dcd83aaf TT |
806 | } |
807 | ||
808 | return 0; | |
809 | ||
11d4d321 | 810 | err_deregister_tty_driver: |
0524513a JS |
811 | ehv_bc_driver = NULL; |
812 | tty_unregister_driver(driver); | |
9f90a4dd JS |
813 | err_tty_driver_kref_put: |
814 | tty_driver_kref_put(driver); | |
11d4d321 | 815 | err_free_bcs: |
dcd83aaf TT |
816 | kfree(bcs); |
817 | ||
818 | return ret; | |
819 | } | |
fc7f47bf | 820 | device_initcall(ehv_bc_init); |