1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * linux/drivers/mmc/core/sdio_io.c
4 *
5 * Copyright 2007-2008 Pierre Ossman
6 */
7
8#include <linux/export.h>
9#include <linux/kernel.h>
10#include <linux/mmc/host.h>
11#include <linux/mmc/card.h>
12#include <linux/mmc/sdio.h>
13#include <linux/mmc/sdio_func.h>
14
15#include "sdio_ops.h"
16#include "core.h"
17#include "card.h"
18#include "host.h"
19
20/**
21 * sdio_claim_host - exclusively claim a bus for a certain SDIO function
22 * @func: SDIO function that will be accessed
23 *
24 * Claim a bus for a set of operations. The SDIO function given
25 * is used to figure out which bus is relevant.
26 */
27void sdio_claim_host(struct sdio_func *func)
28{
29 if (WARN_ON(!func))
30 return;
31
32 mmc_claim_host(host: func->card->host);
33}
34EXPORT_SYMBOL_GPL(sdio_claim_host);
35
36/**
37 * sdio_release_host - release a bus for a certain SDIO function
38 * @func: SDIO function that was accessed
39 *
40 * Release a bus, allowing others to claim the bus for their
41 * operations.
42 */
43void sdio_release_host(struct sdio_func *func)
44{
45 if (WARN_ON(!func))
46 return;
47
48 mmc_release_host(host: func->card->host);
49}
50EXPORT_SYMBOL_GPL(sdio_release_host);
51
52/**
53 * sdio_enable_func - enables a SDIO function for usage
54 * @func: SDIO function to enable
55 *
56 * Powers up and activates a SDIO function so that register
57 * access is possible.
58 */
59int sdio_enable_func(struct sdio_func *func)
60{
61 int ret;
62 unsigned char reg;
63 unsigned long timeout;
64
65 if (!func)
66 return -EINVAL;
67
68 pr_debug("SDIO: Enabling device %s...\n", sdio_func_id(func));
69
70 ret = mmc_io_rw_direct(card: func->card, write: 0, fn: 0, SDIO_CCCR_IOEx, in: 0, out: &reg);
71 if (ret)
72 goto err;
73
74 reg |= 1 << func->num;
75
76 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: 0, SDIO_CCCR_IOEx, in: reg, NULL);
77 if (ret)
78 goto err;
79
80 timeout = jiffies + msecs_to_jiffies(m: func->enable_timeout);
81
82 while (1) {
83 ret = mmc_io_rw_direct(card: func->card, write: 0, fn: 0, SDIO_CCCR_IORx, in: 0, out: &reg);
84 if (ret)
85 goto err;
86 if (reg & (1 << func->num))
87 break;
88 ret = -ETIME;
89 if (time_after(jiffies, timeout))
90 goto err;
91 }
92
93 pr_debug("SDIO: Enabled device %s\n", sdio_func_id(func));
94
95 return 0;
96
97err:
98 pr_debug("SDIO: Failed to enable device %s\n", sdio_func_id(func));
99 return ret;
100}
101EXPORT_SYMBOL_GPL(sdio_enable_func);
102
103/**
104 * sdio_disable_func - disable a SDIO function
105 * @func: SDIO function to disable
106 *
107 * Powers down and deactivates a SDIO function. Register access
108 * to this function will fail until the function is reenabled.
109 */
110int sdio_disable_func(struct sdio_func *func)
111{
112 int ret;
113 unsigned char reg;
114
115 if (!func)
116 return -EINVAL;
117
118 pr_debug("SDIO: Disabling device %s...\n", sdio_func_id(func));
119
120 ret = mmc_io_rw_direct(card: func->card, write: 0, fn: 0, SDIO_CCCR_IOEx, in: 0, out: &reg);
121 if (ret)
122 goto err;
123
124 reg &= ~(1 << func->num);
125
126 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: 0, SDIO_CCCR_IOEx, in: reg, NULL);
127 if (ret)
128 goto err;
129
130 pr_debug("SDIO: Disabled device %s\n", sdio_func_id(func));
131
132 return 0;
133
134err:
135 pr_debug("SDIO: Failed to disable device %s\n", sdio_func_id(func));
136 return ret;
137}
138EXPORT_SYMBOL_GPL(sdio_disable_func);
139
140/**
141 * sdio_set_block_size - set the block size of an SDIO function
142 * @func: SDIO function to change
143 * @blksz: new block size or 0 to use the default.
144 *
145 * The default block size is the largest supported by both the function
146 * and the host, with a maximum of 512 to ensure that arbitrarily sized
147 * data transfer use the optimal (least) number of commands.
148 *
149 * A driver may call this to override the default block size set by the
150 * core. This can be used to set a block size greater than the maximum
151 * that reported by the card; it is the driver's responsibility to ensure
152 * it uses a value that the card supports.
153 *
154 * Returns 0 on success, -EINVAL if the host does not support the
155 * requested block size, or -EIO (etc.) if one of the resultant FBR block
156 * size register writes failed.
157 *
158 */
159int sdio_set_block_size(struct sdio_func *func, unsigned blksz)
160{
161 int ret;
162
163 if (blksz > func->card->host->max_blk_size)
164 return -EINVAL;
165
166 if (blksz == 0) {
167 blksz = min(func->max_blksize, func->card->host->max_blk_size);
168 blksz = min(blksz, 512u);
169 }
170
171 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: 0,
172 SDIO_FBR_BASE(func->num) + SDIO_FBR_BLKSIZE,
173 in: blksz & 0xff, NULL);
174 if (ret)
175 return ret;
176 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: 0,
177 SDIO_FBR_BASE(func->num) + SDIO_FBR_BLKSIZE + 1,
178 in: (blksz >> 8) & 0xff, NULL);
179 if (ret)
180 return ret;
181 func->cur_blksize = blksz;
182 return 0;
183}
184EXPORT_SYMBOL_GPL(sdio_set_block_size);
185
186/*
187 * Calculate the maximum byte mode transfer size
188 */
189static inline unsigned int sdio_max_byte_size(struct sdio_func *func)
190{
191 unsigned mval = func->card->host->max_blk_size;
192
193 if (mmc_blksz_for_byte_mode(c: func->card))
194 mval = min(mval, func->cur_blksize);
195 else
196 mval = min(mval, func->max_blksize);
197
198 if (mmc_card_broken_byte_mode_512(c: func->card))
199 return min(mval, 511u);
200
201 return min(mval, 512u); /* maximum size for byte mode */
202}
203
204/*
205 * This is legacy code, which needs to be re-worked some day. Basically we need
206 * to take into account the properties of the host, as to enable the SDIO func
207 * driver layer to allocate optimal buffers.
208 */
209static inline unsigned int _sdio_align_size(unsigned int sz)
210{
211 /*
212 * FIXME: We don't have a system for the controller to tell
213 * the core about its problems yet, so for now we just 32-bit
214 * align the size.
215 */
216 return ALIGN(sz, 4);
217}
218
219/**
220 * sdio_align_size - pads a transfer size to a more optimal value
221 * @func: SDIO function
222 * @sz: original transfer size
223 *
224 * Pads the original data size with a number of extra bytes in
225 * order to avoid controller bugs and/or performance hits
226 * (e.g. some controllers revert to PIO for certain sizes).
227 *
228 * If possible, it will also adjust the size so that it can be
229 * handled in just a single request.
230 *
231 * Returns the improved size, which might be unmodified.
232 */
233unsigned int sdio_align_size(struct sdio_func *func, unsigned int sz)
234{
235 unsigned int orig_sz;
236 unsigned int blk_sz, byte_sz;
237 unsigned chunk_sz;
238
239 orig_sz = sz;
240
241 /*
242 * Do a first check with the controller, in case it
243 * wants to increase the size up to a point where it
244 * might need more than one block.
245 */
246 sz = _sdio_align_size(sz);
247
248 /*
249 * If we can still do this with just a byte transfer, then
250 * we're done.
251 */
252 if (sz <= sdio_max_byte_size(func))
253 return sz;
254
255 if (func->card->cccr.multi_block) {
256 /*
257 * Check if the transfer is already block aligned
258 */
259 if ((sz % func->cur_blksize) == 0)
260 return sz;
261
262 /*
263 * Realign it so that it can be done with one request,
264 * and recheck if the controller still likes it.
265 */
266 blk_sz = ((sz + func->cur_blksize - 1) /
267 func->cur_blksize) * func->cur_blksize;
268 blk_sz = _sdio_align_size(sz: blk_sz);
269
270 /*
271 * This value is only good if it is still just
272 * one request.
273 */
274 if ((blk_sz % func->cur_blksize) == 0)
275 return blk_sz;
276
277 /*
278 * We failed to do one request, but at least try to
279 * pad the remainder properly.
280 */
281 byte_sz = _sdio_align_size(sz: sz % func->cur_blksize);
282 if (byte_sz <= sdio_max_byte_size(func)) {
283 blk_sz = sz / func->cur_blksize;
284 return blk_sz * func->cur_blksize + byte_sz;
285 }
286 } else {
287 /*
288 * We need multiple requests, so first check that the
289 * controller can handle the chunk size;
290 */
291 chunk_sz = _sdio_align_size(sz: sdio_max_byte_size(func));
292 if (chunk_sz == sdio_max_byte_size(func)) {
293 /*
294 * Fix up the size of the remainder (if any)
295 */
296 byte_sz = orig_sz % chunk_sz;
297 if (byte_sz) {
298 byte_sz = _sdio_align_size(sz: byte_sz);
299 }
300
301 return (orig_sz / chunk_sz) * chunk_sz + byte_sz;
302 }
303 }
304
305 /*
306 * The controller is simply incapable of transferring the size
307 * we want in decent manner, so just return the original size.
308 */
309 return orig_sz;
310}
311EXPORT_SYMBOL_GPL(sdio_align_size);
312
313/* Split an arbitrarily sized data transfer into several
314 * IO_RW_EXTENDED commands. */
315static int sdio_io_rw_ext_helper(struct sdio_func *func, int write,
316 unsigned addr, int incr_addr, u8 *buf, unsigned size)
317{
318 unsigned remainder = size;
319 unsigned max_blocks;
320 int ret;
321
322 if (!func || (func->num > 7))
323 return -EINVAL;
324
325 /* Do the bulk of the transfer using block mode (if supported). */
326 if (func->card->cccr.multi_block && (size > sdio_max_byte_size(func))) {
327 /* Blocks per command is limited by host count, host transfer
328 * size and the maximum for IO_RW_EXTENDED of 511 blocks. */
329 max_blocks = min(func->card->host->max_blk_count, 511u);
330
331 while (remainder >= func->cur_blksize) {
332 unsigned blocks;
333
334 blocks = remainder / func->cur_blksize;
335 if (blocks > max_blocks)
336 blocks = max_blocks;
337 size = blocks * func->cur_blksize;
338
339 ret = mmc_io_rw_extended(card: func->card, write,
340 fn: func->num, addr, incr_addr, buf,
341 blocks, blksz: func->cur_blksize);
342 if (ret)
343 return ret;
344
345 remainder -= size;
346 buf += size;
347 if (incr_addr)
348 addr += size;
349 }
350 }
351
352 /* Write the remainder using byte mode. */
353 while (remainder > 0) {
354 size = min(remainder, sdio_max_byte_size(func));
355
356 /* Indicate byte mode by setting "blocks" = 0 */
357 ret = mmc_io_rw_extended(card: func->card, write, fn: func->num, addr,
358 incr_addr, buf, blocks: 0, blksz: size);
359 if (ret)
360 return ret;
361
362 remainder -= size;
363 buf += size;
364 if (incr_addr)
365 addr += size;
366 }
367 return 0;
368}
369
370/**
371 * sdio_readb - read a single byte from a SDIO function
372 * @func: SDIO function to access
373 * @addr: address to read
374 * @err_ret: optional status value from transfer
375 *
376 * Reads a single byte from the address space of a given SDIO
377 * function. If there is a problem reading the address, 0xff
378 * is returned and @err_ret will contain the error code.
379 */
380u8 sdio_readb(struct sdio_func *func, unsigned int addr, int *err_ret)
381{
382 int ret;
383 u8 val;
384
385 if (!func) {
386 if (err_ret)
387 *err_ret = -EINVAL;
388 return 0xFF;
389 }
390
391 ret = mmc_io_rw_direct(card: func->card, write: 0, fn: func->num, addr, in: 0, out: &val);
392 if (err_ret)
393 *err_ret = ret;
394 if (ret)
395 return 0xFF;
396
397 return val;
398}
399EXPORT_SYMBOL_GPL(sdio_readb);
400
401/**
402 * sdio_writeb - write a single byte to a SDIO function
403 * @func: SDIO function to access
404 * @b: byte to write
405 * @addr: address to write to
406 * @err_ret: optional status value from transfer
407 *
408 * Writes a single byte to the address space of a given SDIO
409 * function. @err_ret will contain the status of the actual
410 * transfer.
411 */
412void sdio_writeb(struct sdio_func *func, u8 b, unsigned int addr, int *err_ret)
413{
414 int ret;
415
416 if (!func) {
417 if (err_ret)
418 *err_ret = -EINVAL;
419 return;
420 }
421
422 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: func->num, addr, in: b, NULL);
423 if (err_ret)
424 *err_ret = ret;
425}
426EXPORT_SYMBOL_GPL(sdio_writeb);
427
428/**
429 * sdio_writeb_readb - write and read a byte from SDIO function
430 * @func: SDIO function to access
431 * @write_byte: byte to write
432 * @addr: address to write to
433 * @err_ret: optional status value from transfer
434 *
435 * Performs a RAW (Read after Write) operation as defined by SDIO spec -
436 * single byte is written to address space of a given SDIO function and
437 * response is read back from the same address, both using single request.
438 * If there is a problem with the operation, 0xff is returned and
439 * @err_ret will contain the error code.
440 */
441u8 sdio_writeb_readb(struct sdio_func *func, u8 write_byte,
442 unsigned int addr, int *err_ret)
443{
444 int ret;
445 u8 val;
446
447 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: func->num, addr,
448 in: write_byte, out: &val);
449 if (err_ret)
450 *err_ret = ret;
451 if (ret)
452 return 0xff;
453
454 return val;
455}
456EXPORT_SYMBOL_GPL(sdio_writeb_readb);
457
458/**
459 * sdio_memcpy_fromio - read a chunk of memory from a SDIO function
460 * @func: SDIO function to access
461 * @dst: buffer to store the data
462 * @addr: address to begin reading from
463 * @count: number of bytes to read
464 *
465 * Reads from the address space of a given SDIO function. Return
466 * value indicates if the transfer succeeded or not.
467 */
468int sdio_memcpy_fromio(struct sdio_func *func, void *dst,
469 unsigned int addr, int count)
470{
471 return sdio_io_rw_ext_helper(func, write: 0, addr, incr_addr: 1, buf: dst, size: count);
472}
473EXPORT_SYMBOL_GPL(sdio_memcpy_fromio);
474
475/**
476 * sdio_memcpy_toio - write a chunk of memory to a SDIO function
477 * @func: SDIO function to access
478 * @addr: address to start writing to
479 * @src: buffer that contains the data to write
480 * @count: number of bytes to write
481 *
482 * Writes to the address space of a given SDIO function. Return
483 * value indicates if the transfer succeeded or not.
484 */
485int sdio_memcpy_toio(struct sdio_func *func, unsigned int addr,
486 void *src, int count)
487{
488 return sdio_io_rw_ext_helper(func, write: 1, addr, incr_addr: 1, buf: src, size: count);
489}
490EXPORT_SYMBOL_GPL(sdio_memcpy_toio);
491
492/**
493 * sdio_readsb - read from a FIFO on a SDIO function
494 * @func: SDIO function to access
495 * @dst: buffer to store the data
496 * @addr: address of (single byte) FIFO
497 * @count: number of bytes to read
498 *
499 * Reads from the specified FIFO of a given SDIO function. Return
500 * value indicates if the transfer succeeded or not.
501 */
502int sdio_readsb(struct sdio_func *func, void *dst, unsigned int addr,
503 int count)
504{
505 return sdio_io_rw_ext_helper(func, write: 0, addr, incr_addr: 0, buf: dst, size: count);
506}
507EXPORT_SYMBOL_GPL(sdio_readsb);
508
509/**
510 * sdio_writesb - write to a FIFO of a SDIO function
511 * @func: SDIO function to access
512 * @addr: address of (single byte) FIFO
513 * @src: buffer that contains the data to write
514 * @count: number of bytes to write
515 *
516 * Writes to the specified FIFO of a given SDIO function. Return
517 * value indicates if the transfer succeeded or not.
518 */
519int sdio_writesb(struct sdio_func *func, unsigned int addr, void *src,
520 int count)
521{
522 return sdio_io_rw_ext_helper(func, write: 1, addr, incr_addr: 0, buf: src, size: count);
523}
524EXPORT_SYMBOL_GPL(sdio_writesb);
525
526/**
527 * sdio_readw - read a 16 bit integer from a SDIO function
528 * @func: SDIO function to access
529 * @addr: address to read
530 * @err_ret: optional status value from transfer
531 *
532 * Reads a 16 bit integer from the address space of a given SDIO
533 * function. If there is a problem reading the address, 0xffff
534 * is returned and @err_ret will contain the error code.
535 */
536u16 sdio_readw(struct sdio_func *func, unsigned int addr, int *err_ret)
537{
538 int ret;
539
540 ret = sdio_memcpy_fromio(func, func->tmpbuf, addr, 2);
541 if (err_ret)
542 *err_ret = ret;
543 if (ret)
544 return 0xFFFF;
545
546 return le16_to_cpup(p: (__le16 *)func->tmpbuf);
547}
548EXPORT_SYMBOL_GPL(sdio_readw);
549
550/**
551 * sdio_writew - write a 16 bit integer to a SDIO function
552 * @func: SDIO function to access
553 * @b: integer to write
554 * @addr: address to write to
555 * @err_ret: optional status value from transfer
556 *
557 * Writes a 16 bit integer to the address space of a given SDIO
558 * function. @err_ret will contain the status of the actual
559 * transfer.
560 */
561void sdio_writew(struct sdio_func *func, u16 b, unsigned int addr, int *err_ret)
562{
563 int ret;
564
565 *(__le16 *)func->tmpbuf = cpu_to_le16(b);
566
567 ret = sdio_memcpy_toio(func, addr, func->tmpbuf, 2);
568 if (err_ret)
569 *err_ret = ret;
570}
571EXPORT_SYMBOL_GPL(sdio_writew);
572
573/**
574 * sdio_readl - read a 32 bit integer from a SDIO function
575 * @func: SDIO function to access
576 * @addr: address to read
577 * @err_ret: optional status value from transfer
578 *
579 * Reads a 32 bit integer from the address space of a given SDIO
580 * function. If there is a problem reading the address,
581 * 0xffffffff is returned and @err_ret will contain the error
582 * code.
583 */
584u32 sdio_readl(struct sdio_func *func, unsigned int addr, int *err_ret)
585{
586 int ret;
587
588 ret = sdio_memcpy_fromio(func, func->tmpbuf, addr, 4);
589 if (err_ret)
590 *err_ret = ret;
591 if (ret)
592 return 0xFFFFFFFF;
593
594 return le32_to_cpup(p: (__le32 *)func->tmpbuf);
595}
596EXPORT_SYMBOL_GPL(sdio_readl);
597
598/**
599 * sdio_writel - write a 32 bit integer to a SDIO function
600 * @func: SDIO function to access
601 * @b: integer to write
602 * @addr: address to write to
603 * @err_ret: optional status value from transfer
604 *
605 * Writes a 32 bit integer to the address space of a given SDIO
606 * function. @err_ret will contain the status of the actual
607 * transfer.
608 */
609void sdio_writel(struct sdio_func *func, u32 b, unsigned int addr, int *err_ret)
610{
611 int ret;
612
613 *(__le32 *)func->tmpbuf = cpu_to_le32(b);
614
615 ret = sdio_memcpy_toio(func, addr, func->tmpbuf, 4);
616 if (err_ret)
617 *err_ret = ret;
618}
619EXPORT_SYMBOL_GPL(sdio_writel);
620
621/**
622 * sdio_f0_readb - read a single byte from SDIO function 0
623 * @func: an SDIO function of the card
624 * @addr: address to read
625 * @err_ret: optional status value from transfer
626 *
627 * Reads a single byte from the address space of SDIO function 0.
628 * If there is a problem reading the address, 0xff is returned
629 * and @err_ret will contain the error code.
630 */
631unsigned char sdio_f0_readb(struct sdio_func *func, unsigned int addr,
632 int *err_ret)
633{
634 int ret;
635 unsigned char val;
636
637 if (!func) {
638 if (err_ret)
639 *err_ret = -EINVAL;
640 return 0xFF;
641 }
642
643 ret = mmc_io_rw_direct(card: func->card, write: 0, fn: 0, addr, in: 0, out: &val);
644 if (err_ret)
645 *err_ret = ret;
646 if (ret)
647 return 0xFF;
648
649 return val;
650}
651EXPORT_SYMBOL_GPL(sdio_f0_readb);
652
653/**
654 * sdio_f0_writeb - write a single byte to SDIO function 0
655 * @func: an SDIO function of the card
656 * @b: byte to write
657 * @addr: address to write to
658 * @err_ret: optional status value from transfer
659 *
660 * Writes a single byte to the address space of SDIO function 0.
661 * @err_ret will contain the status of the actual transfer.
662 *
663 * Only writes to the vendor specific CCCR registers (0xF0 -
664 * 0xFF) are permiited; @err_ret will be set to -EINVAL for *
665 * writes outside this range.
666 */
667void sdio_f0_writeb(struct sdio_func *func, unsigned char b, unsigned int addr,
668 int *err_ret)
669{
670 int ret;
671
672 if (!func) {
673 if (err_ret)
674 *err_ret = -EINVAL;
675 return;
676 }
677
678 if ((addr < 0xF0 || addr > 0xFF) && (!mmc_card_lenient_fn0(c: func->card))) {
679 if (err_ret)
680 *err_ret = -EINVAL;
681 return;
682 }
683
684 ret = mmc_io_rw_direct(card: func->card, write: 1, fn: 0, addr, in: b, NULL);
685 if (err_ret)
686 *err_ret = ret;
687}
688EXPORT_SYMBOL_GPL(sdio_f0_writeb);
689
690/**
691 * sdio_get_host_pm_caps - get host power management capabilities
692 * @func: SDIO function attached to host
693 *
694 * Returns a capability bitmask corresponding to power management
695 * features supported by the host controller that the card function
696 * might rely upon during a system suspend. The host doesn't need
697 * to be claimed, nor the function active, for this information to be
698 * obtained.
699 */
700mmc_pm_flag_t sdio_get_host_pm_caps(struct sdio_func *func)
701{
702 if (!func)
703 return 0;
704
705 return func->card->host->pm_caps;
706}
707EXPORT_SYMBOL_GPL(sdio_get_host_pm_caps);
708
709/**
710 * sdio_set_host_pm_flags - set wanted host power management capabilities
711 * @func: SDIO function attached to host
712 * @flags: Power Management flags to set
713 *
714 * Set a capability bitmask corresponding to wanted host controller
715 * power management features for the upcoming suspend state.
716 * This must be called, if needed, each time the suspend method of
717 * the function driver is called, and must contain only bits that
718 * were returned by sdio_get_host_pm_caps().
719 * The host doesn't need to be claimed, nor the function active,
720 * for this information to be set.
721 */
722int sdio_set_host_pm_flags(struct sdio_func *func, mmc_pm_flag_t flags)
723{
724 struct mmc_host *host;
725
726 if (!func)
727 return -EINVAL;
728
729 host = func->card->host;
730
731 if (flags & ~host->pm_caps)
732 return -EINVAL;
733
734 /* function suspend methods are serialized, hence no lock needed */
735 host->pm_flags |= flags;
736 return 0;
737}
738EXPORT_SYMBOL_GPL(sdio_set_host_pm_flags);
739
740/**
741 * sdio_retune_crc_disable - temporarily disable retuning on CRC errors
742 * @func: SDIO function attached to host
743 *
744 * If the SDIO card is known to be in a state where it might produce
745 * CRC errors on the bus in response to commands (like if we know it is
746 * transitioning between power states), an SDIO function driver can
747 * call this function to temporarily disable the SD/MMC core behavior of
748 * triggering an automatic retuning.
749 *
750 * This function should be called while the host is claimed and the host
751 * should remain claimed until sdio_retune_crc_enable() is called.
752 * Specifically, the expected sequence of calls is:
753 * - sdio_claim_host()
754 * - sdio_retune_crc_disable()
755 * - some number of calls like sdio_writeb() and sdio_readb()
756 * - sdio_retune_crc_enable()
757 * - sdio_release_host()
758 */
759void sdio_retune_crc_disable(struct sdio_func *func)
760{
761 func->card->host->retune_crc_disable = true;
762}
763EXPORT_SYMBOL_GPL(sdio_retune_crc_disable);
764
765/**
766 * sdio_retune_crc_enable - re-enable retuning on CRC errors
767 * @func: SDIO function attached to host
768 *
769 * This is the complement to sdio_retune_crc_disable().
770 */
771void sdio_retune_crc_enable(struct sdio_func *func)
772{
773 func->card->host->retune_crc_disable = false;
774}
775EXPORT_SYMBOL_GPL(sdio_retune_crc_enable);
776
777/**
778 * sdio_retune_hold_now - start deferring retuning requests till release
779 * @func: SDIO function attached to host
780 *
781 * This function can be called if it's currently a bad time to do
782 * a retune of the SDIO card. Retune requests made during this time
783 * will be held and we'll actually do the retune sometime after the
784 * release.
785 *
786 * This function could be useful if an SDIO card is in a power state
787 * where it can respond to a small subset of commands that doesn't
788 * include the retuning command. Care should be taken when using
789 * this function since (presumably) the retuning request we might be
790 * deferring was made for a good reason.
791 *
792 * This function should be called while the host is claimed.
793 */
794void sdio_retune_hold_now(struct sdio_func *func)
795{
796 mmc_retune_hold_now(host: func->card->host);
797}
798EXPORT_SYMBOL_GPL(sdio_retune_hold_now);
799
800/**
801 * sdio_retune_release - signal that it's OK to retune now
802 * @func: SDIO function attached to host
803 *
804 * This is the complement to sdio_retune_hold_now(). Calling this
805 * function won't make a retune happen right away but will allow
806 * them to be scheduled normally.
807 *
808 * This function should be called while the host is claimed.
809 */
810void sdio_retune_release(struct sdio_func *func)
811{
812 mmc_retune_release(host: func->card->host);
813}
814EXPORT_SYMBOL_GPL(sdio_retune_release);
815

source code of linux/drivers/mmc/core/sdio_io.c