xref: /linux/drivers/mmc/core/host.c (revision bb5b94f5bbe75470912b70fb08880fc5273aa62d)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/drivers/mmc/core/host.c
4  *
5  *  Copyright (C) 2003 Russell King, All Rights Reserved.
6  *  Copyright (C) 2007-2008 Pierre Ossman
7  *  Copyright (C) 2010 Linus Walleij
8  *
9  *  MMC host class device management
10  */
11 
12 #include <linux/device.h>
13 #include <linux/err.h>
14 #include <linux/idr.h>
15 #include <linux/of.h>
16 #include <linux/of_gpio.h>
17 #include <linux/pagemap.h>
18 #include <linux/pm_wakeup.h>
19 #include <linux/export.h>
20 #include <linux/leds.h>
21 #include <linux/slab.h>
22 
23 #include <linux/mmc/host.h>
24 #include <linux/mmc/card.h>
25 #include <linux/mmc/slot-gpio.h>
26 
27 #include "core.h"
28 #include "crypto.h"
29 #include "host.h"
30 #include "slot-gpio.h"
31 #include "pwrseq.h"
32 #include "sdio_ops.h"
33 
34 #define cls_dev_to_mmc_host(d)	container_of(d, struct mmc_host, class_dev)
35 
36 static DEFINE_IDA(mmc_host_ida);
37 
38 #ifdef CONFIG_PM_SLEEP
39 static int mmc_host_class_prepare(struct device *dev)
40 {
41 	struct mmc_host *host = cls_dev_to_mmc_host(dev);
42 
43 	/*
44 	 * It's safe to access the bus_ops pointer, as both userspace and the
45 	 * workqueue for detecting cards are frozen at this point.
46 	 */
47 	if (!host->bus_ops)
48 		return 0;
49 
50 	/* Validate conditions for system suspend. */
51 	if (host->bus_ops->pre_suspend)
52 		return host->bus_ops->pre_suspend(host);
53 
54 	return 0;
55 }
56 
57 static void mmc_host_class_complete(struct device *dev)
58 {
59 	struct mmc_host *host = cls_dev_to_mmc_host(dev);
60 
61 	_mmc_detect_change(host, 0, false);
62 }
63 
64 static const struct dev_pm_ops mmc_host_class_dev_pm_ops = {
65 	.prepare = mmc_host_class_prepare,
66 	.complete = mmc_host_class_complete,
67 };
68 
69 #define MMC_HOST_CLASS_DEV_PM_OPS (&mmc_host_class_dev_pm_ops)
70 #else
71 #define MMC_HOST_CLASS_DEV_PM_OPS NULL
72 #endif
73 
74 static void mmc_host_classdev_release(struct device *dev)
75 {
76 	struct mmc_host *host = cls_dev_to_mmc_host(dev);
77 	wakeup_source_unregister(host->ws);
78 	if (of_alias_get_id(host->parent->of_node, "mmc") < 0)
79 		ida_simple_remove(&mmc_host_ida, host->index);
80 	kfree(host);
81 }
82 
83 static struct class mmc_host_class = {
84 	.name		= "mmc_host",
85 	.dev_release	= mmc_host_classdev_release,
86 	.pm		= MMC_HOST_CLASS_DEV_PM_OPS,
87 };
88 
89 int mmc_register_host_class(void)
90 {
91 	return class_register(&mmc_host_class);
92 }
93 
94 void mmc_unregister_host_class(void)
95 {
96 	class_unregister(&mmc_host_class);
97 }
98 
99 void mmc_retune_enable(struct mmc_host *host)
100 {
101 	host->can_retune = 1;
102 	if (host->retune_period)
103 		mod_timer(&host->retune_timer,
104 			  jiffies + host->retune_period * HZ);
105 }
106 
107 /*
108  * Pause re-tuning for a small set of operations.  The pause begins after the
109  * next command and after first doing re-tuning.
110  */
111 void mmc_retune_pause(struct mmc_host *host)
112 {
113 	if (!host->retune_paused) {
114 		host->retune_paused = 1;
115 		mmc_retune_needed(host);
116 		mmc_retune_hold(host);
117 	}
118 }
119 EXPORT_SYMBOL(mmc_retune_pause);
120 
121 void mmc_retune_unpause(struct mmc_host *host)
122 {
123 	if (host->retune_paused) {
124 		host->retune_paused = 0;
125 		mmc_retune_release(host);
126 	}
127 }
128 EXPORT_SYMBOL(mmc_retune_unpause);
129 
130 void mmc_retune_disable(struct mmc_host *host)
131 {
132 	mmc_retune_unpause(host);
133 	host->can_retune = 0;
134 	del_timer_sync(&host->retune_timer);
135 	host->retune_now = 0;
136 	host->need_retune = 0;
137 }
138 
139 void mmc_retune_timer_stop(struct mmc_host *host)
140 {
141 	del_timer_sync(&host->retune_timer);
142 }
143 EXPORT_SYMBOL(mmc_retune_timer_stop);
144 
145 void mmc_retune_hold(struct mmc_host *host)
146 {
147 	if (!host->hold_retune)
148 		host->retune_now = 1;
149 	host->hold_retune += 1;
150 }
151 
152 void mmc_retune_release(struct mmc_host *host)
153 {
154 	if (host->hold_retune)
155 		host->hold_retune -= 1;
156 	else
157 		WARN_ON(1);
158 }
159 EXPORT_SYMBOL(mmc_retune_release);
160 
161 int mmc_retune(struct mmc_host *host)
162 {
163 	bool return_to_hs400 = false;
164 	int err;
165 
166 	if (host->retune_now)
167 		host->retune_now = 0;
168 	else
169 		return 0;
170 
171 	if (!host->need_retune || host->doing_retune || !host->card)
172 		return 0;
173 
174 	host->need_retune = 0;
175 
176 	host->doing_retune = 1;
177 
178 	if (host->ios.timing == MMC_TIMING_MMC_HS400) {
179 		err = mmc_hs400_to_hs200(host->card);
180 		if (err)
181 			goto out;
182 
183 		return_to_hs400 = true;
184 	}
185 
186 	err = mmc_execute_tuning(host->card);
187 	if (err)
188 		goto out;
189 
190 	if (return_to_hs400)
191 		err = mmc_hs200_to_hs400(host->card);
192 out:
193 	host->doing_retune = 0;
194 
195 	return err;
196 }
197 
198 static void mmc_retune_timer(struct timer_list *t)
199 {
200 	struct mmc_host *host = from_timer(host, t, retune_timer);
201 
202 	mmc_retune_needed(host);
203 }
204 
205 static void mmc_of_parse_timing_phase(struct device *dev, const char *prop,
206 				      struct mmc_clk_phase *phase)
207 {
208 	int degrees[2] = {0};
209 	int rc;
210 
211 	rc = device_property_read_u32_array(dev, prop, degrees, 2);
212 	phase->valid = !rc;
213 	if (phase->valid) {
214 		phase->in_deg = degrees[0];
215 		phase->out_deg = degrees[1];
216 	}
217 }
218 
219 void
220 mmc_of_parse_clk_phase(struct mmc_host *host, struct mmc_clk_phase_map *map)
221 {
222 	struct device *dev = host->parent;
223 
224 	mmc_of_parse_timing_phase(dev, "clk-phase-legacy",
225 				  &map->phase[MMC_TIMING_LEGACY]);
226 	mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs",
227 				  &map->phase[MMC_TIMING_MMC_HS]);
228 	mmc_of_parse_timing_phase(dev, "clk-phase-sd-hs",
229 				  &map->phase[MMC_TIMING_SD_HS]);
230 	mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr12",
231 				  &map->phase[MMC_TIMING_UHS_SDR12]);
232 	mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr25",
233 				  &map->phase[MMC_TIMING_UHS_SDR25]);
234 	mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr50",
235 				  &map->phase[MMC_TIMING_UHS_SDR50]);
236 	mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr104",
237 				  &map->phase[MMC_TIMING_UHS_SDR104]);
238 	mmc_of_parse_timing_phase(dev, "clk-phase-uhs-ddr50",
239 				  &map->phase[MMC_TIMING_UHS_DDR50]);
240 	mmc_of_parse_timing_phase(dev, "clk-phase-mmc-ddr52",
241 				  &map->phase[MMC_TIMING_MMC_DDR52]);
242 	mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs200",
243 				  &map->phase[MMC_TIMING_MMC_HS200]);
244 	mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs400",
245 				  &map->phase[MMC_TIMING_MMC_HS400]);
246 }
247 EXPORT_SYMBOL(mmc_of_parse_clk_phase);
248 
249 /**
250  * mmc_of_parse() - parse host's device properties
251  * @host: host whose properties should be parsed.
252  *
253  * To keep the rest of the MMC subsystem unaware of whether DT has been
254  * used to to instantiate and configure this host instance or not, we
255  * parse the properties and set respective generic mmc-host flags and
256  * parameters.
257  */
258 int mmc_of_parse(struct mmc_host *host)
259 {
260 	struct device *dev = host->parent;
261 	u32 bus_width, drv_type, cd_debounce_delay_ms;
262 	int ret;
263 
264 	if (!dev || !dev_fwnode(dev))
265 		return 0;
266 
267 	/* "bus-width" is translated to MMC_CAP_*_BIT_DATA flags */
268 	if (device_property_read_u32(dev, "bus-width", &bus_width) < 0) {
269 		dev_dbg(host->parent,
270 			"\"bus-width\" property is missing, assuming 1 bit.\n");
271 		bus_width = 1;
272 	}
273 
274 	switch (bus_width) {
275 	case 8:
276 		host->caps |= MMC_CAP_8_BIT_DATA;
277 		fallthrough;	/* Hosts capable of 8-bit can also do 4 bits */
278 	case 4:
279 		host->caps |= MMC_CAP_4_BIT_DATA;
280 		break;
281 	case 1:
282 		break;
283 	default:
284 		dev_err(host->parent,
285 			"Invalid \"bus-width\" value %u!\n", bus_width);
286 		return -EINVAL;
287 	}
288 
289 	/* f_max is obtained from the optional "max-frequency" property */
290 	device_property_read_u32(dev, "max-frequency", &host->f_max);
291 
292 	/*
293 	 * Configure CD and WP pins. They are both by default active low to
294 	 * match the SDHCI spec. If GPIOs are provided for CD and / or WP, the
295 	 * mmc-gpio helpers are used to attach, configure and use them. If
296 	 * polarity inversion is specified in DT, one of MMC_CAP2_CD_ACTIVE_HIGH
297 	 * and MMC_CAP2_RO_ACTIVE_HIGH capability-2 flags is set. If the
298 	 * "broken-cd" property is provided, the MMC_CAP_NEEDS_POLL capability
299 	 * is set. If the "non-removable" property is found, the
300 	 * MMC_CAP_NONREMOVABLE capability is set and no card-detection
301 	 * configuration is performed.
302 	 */
303 
304 	/* Parse Card Detection */
305 
306 	if (device_property_read_bool(dev, "non-removable")) {
307 		host->caps |= MMC_CAP_NONREMOVABLE;
308 	} else {
309 		if (device_property_read_bool(dev, "cd-inverted"))
310 			host->caps2 |= MMC_CAP2_CD_ACTIVE_HIGH;
311 
312 		if (device_property_read_u32(dev, "cd-debounce-delay-ms",
313 					     &cd_debounce_delay_ms))
314 			cd_debounce_delay_ms = 200;
315 
316 		if (device_property_read_bool(dev, "broken-cd"))
317 			host->caps |= MMC_CAP_NEEDS_POLL;
318 
319 		ret = mmc_gpiod_request_cd(host, "cd", 0, false,
320 					   cd_debounce_delay_ms * 1000);
321 		if (!ret)
322 			dev_info(host->parent, "Got CD GPIO\n");
323 		else if (ret != -ENOENT && ret != -ENOSYS)
324 			return ret;
325 	}
326 
327 	/* Parse Write Protection */
328 
329 	if (device_property_read_bool(dev, "wp-inverted"))
330 		host->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
331 
332 	ret = mmc_gpiod_request_ro(host, "wp", 0, 0);
333 	if (!ret)
334 		dev_info(host->parent, "Got WP GPIO\n");
335 	else if (ret != -ENOENT && ret != -ENOSYS)
336 		return ret;
337 
338 	if (device_property_read_bool(dev, "disable-wp"))
339 		host->caps2 |= MMC_CAP2_NO_WRITE_PROTECT;
340 
341 	if (device_property_read_bool(dev, "cap-sd-highspeed"))
342 		host->caps |= MMC_CAP_SD_HIGHSPEED;
343 	if (device_property_read_bool(dev, "cap-mmc-highspeed"))
344 		host->caps |= MMC_CAP_MMC_HIGHSPEED;
345 	if (device_property_read_bool(dev, "sd-uhs-sdr12"))
346 		host->caps |= MMC_CAP_UHS_SDR12;
347 	if (device_property_read_bool(dev, "sd-uhs-sdr25"))
348 		host->caps |= MMC_CAP_UHS_SDR25;
349 	if (device_property_read_bool(dev, "sd-uhs-sdr50"))
350 		host->caps |= MMC_CAP_UHS_SDR50;
351 	if (device_property_read_bool(dev, "sd-uhs-sdr104"))
352 		host->caps |= MMC_CAP_UHS_SDR104;
353 	if (device_property_read_bool(dev, "sd-uhs-ddr50"))
354 		host->caps |= MMC_CAP_UHS_DDR50;
355 	if (device_property_read_bool(dev, "cap-power-off-card"))
356 		host->caps |= MMC_CAP_POWER_OFF_CARD;
357 	if (device_property_read_bool(dev, "cap-mmc-hw-reset"))
358 		host->caps |= MMC_CAP_HW_RESET;
359 	if (device_property_read_bool(dev, "cap-sdio-irq"))
360 		host->caps |= MMC_CAP_SDIO_IRQ;
361 	if (device_property_read_bool(dev, "full-pwr-cycle"))
362 		host->caps2 |= MMC_CAP2_FULL_PWR_CYCLE;
363 	if (device_property_read_bool(dev, "full-pwr-cycle-in-suspend"))
364 		host->caps2 |= MMC_CAP2_FULL_PWR_CYCLE_IN_SUSPEND;
365 	if (device_property_read_bool(dev, "keep-power-in-suspend"))
366 		host->pm_caps |= MMC_PM_KEEP_POWER;
367 	if (device_property_read_bool(dev, "wakeup-source") ||
368 	    device_property_read_bool(dev, "enable-sdio-wakeup")) /* legacy */
369 		host->pm_caps |= MMC_PM_WAKE_SDIO_IRQ;
370 	if (device_property_read_bool(dev, "mmc-ddr-3_3v"))
371 		host->caps |= MMC_CAP_3_3V_DDR;
372 	if (device_property_read_bool(dev, "mmc-ddr-1_8v"))
373 		host->caps |= MMC_CAP_1_8V_DDR;
374 	if (device_property_read_bool(dev, "mmc-ddr-1_2v"))
375 		host->caps |= MMC_CAP_1_2V_DDR;
376 	if (device_property_read_bool(dev, "mmc-hs200-1_8v"))
377 		host->caps2 |= MMC_CAP2_HS200_1_8V_SDR;
378 	if (device_property_read_bool(dev, "mmc-hs200-1_2v"))
379 		host->caps2 |= MMC_CAP2_HS200_1_2V_SDR;
380 	if (device_property_read_bool(dev, "mmc-hs400-1_8v"))
381 		host->caps2 |= MMC_CAP2_HS400_1_8V | MMC_CAP2_HS200_1_8V_SDR;
382 	if (device_property_read_bool(dev, "mmc-hs400-1_2v"))
383 		host->caps2 |= MMC_CAP2_HS400_1_2V | MMC_CAP2_HS200_1_2V_SDR;
384 	if (device_property_read_bool(dev, "mmc-hs400-enhanced-strobe"))
385 		host->caps2 |= MMC_CAP2_HS400_ES;
386 	if (device_property_read_bool(dev, "no-sdio"))
387 		host->caps2 |= MMC_CAP2_NO_SDIO;
388 	if (device_property_read_bool(dev, "no-sd"))
389 		host->caps2 |= MMC_CAP2_NO_SD;
390 	if (device_property_read_bool(dev, "no-mmc"))
391 		host->caps2 |= MMC_CAP2_NO_MMC;
392 	if (device_property_read_bool(dev, "no-mmc-hs400"))
393 		host->caps2 &= ~(MMC_CAP2_HS400_1_8V | MMC_CAP2_HS400_1_2V |
394 				 MMC_CAP2_HS400_ES);
395 
396 	/* Must be after "non-removable" check */
397 	if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
398 		if (host->caps & MMC_CAP_NONREMOVABLE)
399 			host->fixed_drv_type = drv_type;
400 		else
401 			dev_err(host->parent,
402 				"can't use fixed driver type, media is removable\n");
403 	}
404 
405 	host->dsr_req = !device_property_read_u32(dev, "dsr", &host->dsr);
406 	if (host->dsr_req && (host->dsr & ~0xffff)) {
407 		dev_err(host->parent,
408 			"device tree specified broken value for DSR: 0x%x, ignoring\n",
409 			host->dsr);
410 		host->dsr_req = 0;
411 	}
412 
413 	device_property_read_u32(dev, "post-power-on-delay-ms",
414 				 &host->ios.power_delay_ms);
415 
416 	return mmc_pwrseq_alloc(host);
417 }
418 
419 EXPORT_SYMBOL(mmc_of_parse);
420 
421 /**
422  * mmc_of_parse_voltage - return mask of supported voltages
423  * @host: host whose properties should be parsed.
424  * @mask: mask of voltages available for MMC/SD/SDIO
425  *
426  * Parse the "voltage-ranges" property, returning zero if it is not
427  * found, negative errno if the voltage-range specification is invalid,
428  * or one if the voltage-range is specified and successfully parsed.
429  */
430 int mmc_of_parse_voltage(struct mmc_host *host, u32 *mask)
431 {
432 	const char *prop = "voltage-ranges";
433 	struct device *dev = host->parent;
434 	u32 *voltage_ranges;
435 	int num_ranges, i;
436 	int ret;
437 
438 	if (!device_property_present(dev, prop)) {
439 		dev_dbg(dev, "%s unspecified\n", prop);
440 		return 0;
441 	}
442 
443 	ret = device_property_count_u32(dev, prop);
444 	if (ret < 0)
445 		return ret;
446 
447 	num_ranges = ret / 2;
448 	if (!num_ranges) {
449 		dev_err(dev, "%s empty\n", prop);
450 		return -EINVAL;
451 	}
452 
453 	voltage_ranges = kcalloc(2 * num_ranges, sizeof(*voltage_ranges), GFP_KERNEL);
454 	if (!voltage_ranges)
455 		return -ENOMEM;
456 
457 	ret = device_property_read_u32_array(dev, prop, voltage_ranges, 2 * num_ranges);
458 	if (ret) {
459 		kfree(voltage_ranges);
460 		return ret;
461 	}
462 
463 	for (i = 0; i < num_ranges; i++) {
464 		const int j = i * 2;
465 		u32 ocr_mask;
466 
467 		ocr_mask = mmc_vddrange_to_ocrmask(voltage_ranges[j + 0],
468 						   voltage_ranges[j + 1]);
469 		if (!ocr_mask) {
470 			dev_err(dev, "range #%d in %s is invalid\n", i, prop);
471 			kfree(voltage_ranges);
472 			return -EINVAL;
473 		}
474 		*mask |= ocr_mask;
475 	}
476 
477 	kfree(voltage_ranges);
478 
479 	return 1;
480 }
481 EXPORT_SYMBOL(mmc_of_parse_voltage);
482 
483 /**
484  * mmc_first_nonreserved_index() - get the first index that is not reserved
485  */
486 static int mmc_first_nonreserved_index(void)
487 {
488 	int max;
489 
490 	max = of_alias_get_highest_id("mmc");
491 	if (max < 0)
492 		return 0;
493 
494 	return max + 1;
495 }
496 
497 /**
498  *	mmc_alloc_host - initialise the per-host structure.
499  *	@extra: sizeof private data structure
500  *	@dev: pointer to host device model structure
501  *
502  *	Initialise the per-host structure.
503  */
504 struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
505 {
506 	int index;
507 	struct mmc_host *host;
508 	int alias_id, min_idx, max_idx;
509 
510 	host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
511 	if (!host)
512 		return NULL;
513 
514 	/* scanning will be enabled when we're ready */
515 	host->rescan_disable = 1;
516 
517 	alias_id = of_alias_get_id(dev->of_node, "mmc");
518 	if (alias_id >= 0) {
519 		index = alias_id;
520 	} else {
521 		min_idx = mmc_first_nonreserved_index();
522 		max_idx = 0;
523 
524 		index = ida_simple_get(&mmc_host_ida, min_idx, max_idx, GFP_KERNEL);
525 		if (index < 0) {
526 			kfree(host);
527 			return NULL;
528 		}
529 	}
530 
531 	host->index = index;
532 
533 	dev_set_name(&host->class_dev, "mmc%d", host->index);
534 	host->ws = wakeup_source_register(NULL, dev_name(&host->class_dev));
535 
536 	host->parent = dev;
537 	host->class_dev.parent = dev;
538 	host->class_dev.class = &mmc_host_class;
539 	device_initialize(&host->class_dev);
540 	device_enable_async_suspend(&host->class_dev);
541 
542 	if (mmc_gpio_alloc(host)) {
543 		put_device(&host->class_dev);
544 		return NULL;
545 	}
546 
547 	spin_lock_init(&host->lock);
548 	init_waitqueue_head(&host->wq);
549 	INIT_DELAYED_WORK(&host->detect, mmc_rescan);
550 	INIT_DELAYED_WORK(&host->sdio_irq_work, sdio_irq_work);
551 	timer_setup(&host->retune_timer, mmc_retune_timer, 0);
552 
553 	/*
554 	 * By default, hosts do not support SGIO or large requests.
555 	 * They have to set these according to their abilities.
556 	 */
557 	host->max_segs = 1;
558 	host->max_seg_size = PAGE_SIZE;
559 
560 	host->max_req_size = PAGE_SIZE;
561 	host->max_blk_size = 512;
562 	host->max_blk_count = PAGE_SIZE / 512;
563 
564 	host->fixed_drv_type = -EINVAL;
565 	host->ios.power_delay_ms = 10;
566 	host->ios.power_mode = MMC_POWER_UNDEFINED;
567 
568 	return host;
569 }
570 
571 EXPORT_SYMBOL(mmc_alloc_host);
572 
573 /**
574  *	mmc_add_host - initialise host hardware
575  *	@host: mmc host
576  *
577  *	Register the host with the driver model. The host must be
578  *	prepared to start servicing requests before this function
579  *	completes.
580  */
581 int mmc_add_host(struct mmc_host *host)
582 {
583 	int err;
584 
585 	WARN_ON((host->caps & MMC_CAP_SDIO_IRQ) &&
586 		!host->ops->enable_sdio_irq);
587 
588 	err = device_add(&host->class_dev);
589 	if (err)
590 		return err;
591 
592 	led_trigger_register_simple(dev_name(&host->class_dev), &host->led);
593 
594 #ifdef CONFIG_DEBUG_FS
595 	mmc_add_host_debugfs(host);
596 #endif
597 
598 	mmc_start_host(host);
599 	return 0;
600 }
601 
602 EXPORT_SYMBOL(mmc_add_host);
603 
604 /**
605  *	mmc_remove_host - remove host hardware
606  *	@host: mmc host
607  *
608  *	Unregister and remove all cards associated with this host,
609  *	and power down the MMC bus. No new requests will be issued
610  *	after this function has returned.
611  */
612 void mmc_remove_host(struct mmc_host *host)
613 {
614 	mmc_stop_host(host);
615 
616 #ifdef CONFIG_DEBUG_FS
617 	mmc_remove_host_debugfs(host);
618 #endif
619 
620 	device_del(&host->class_dev);
621 
622 	led_trigger_unregister_simple(host->led);
623 }
624 
625 EXPORT_SYMBOL(mmc_remove_host);
626 
627 /**
628  *	mmc_free_host - free the host structure
629  *	@host: mmc host
630  *
631  *	Free the host once all references to it have been dropped.
632  */
633 void mmc_free_host(struct mmc_host *host)
634 {
635 	mmc_pwrseq_free(host);
636 	put_device(&host->class_dev);
637 }
638 
639 EXPORT_SYMBOL(mmc_free_host);
640