1/*
  2 * Generic OPP Interface
  3 *
  4 * Copyright (C) 2009-2010 Texas Instruments Incorporated.
  5 *	Nishanth Menon
  6 *	Romit Dasgupta
  7 *	Kevin Hilman
  8 *
  9 * This program is free software; you can redistribute it and/or modify
 10 * it under the terms of the GNU General Public License version 2 as
 11 * published by the Free Software Foundation.
 12 */
 13
 14#include <linux/kernel.h>
 15#include <linux/errno.h>
 16#include <linux/err.h>
 17#include <linux/init.h>
 18#include <linux/slab.h>
 19#include <linux/cpufreq.h>
 20#include <linux/list.h>
 21#include <linux/rculist.h>
 22#include <linux/rcupdate.h>
 23#include <linux/opp.h>
 24
 25/*
 26 * Internal data structure organization with the OPP layer library is as
 27 * follows:
 28 * dev_opp_list (root)
 29 *	|- device 1 (represents voltage domain 1)
 30 *	|	|- opp 1 (availability, freq, voltage)
 31 *	|	|- opp 2 ..
 32 *	...	...
 33 *	|	`- opp n ..
 34 *	|- device 2 (represents the next voltage domain)
 35 *	...
 36 *	`- device m (represents mth voltage domain)
 37 * device 1, 2.. are represented by dev_opp structure while each opp
 38 * is represented by the opp structure.
 39 */
 40
 41/**
 42 * struct opp - Generic OPP description structure
 43 * @node:	opp list node. The nodes are maintained throughout the lifetime
 44 *		of boot. It is expected only an optimal set of OPPs are
 45 *		added to the library by the SoC framework.
 46 *		RCU usage: opp list is traversed with RCU locks. node
 47 *		modification is possible realtime, hence the modifications
 48 *		are protected by the dev_opp_list_lock for integrity.
 49 *		IMPORTANT: the opp nodes should be maintained in increasing
 50 *		order.
 51 * @available:	true/false - marks if this OPP as available or not
 52 * @rate:	Frequency in hertz
 53 * @u_volt:	Nominal voltage in microvolts corresponding to this OPP
 54 * @dev_opp:	points back to the device_opp struct this opp belongs to
 55 *
 56 * This structure stores the OPP information for a given device.
 57 */
 58struct opp {
 59	struct list_head node;
 60
 61	bool available;
 62	unsigned long rate;
 63	unsigned long u_volt;
 64
 65	struct device_opp *dev_opp;
 66};
 67
 68/**
 69 * struct device_opp - Device opp structure
 70 * @node:	list node - contains the devices with OPPs that
 71 *		have been registered. Nodes once added are not modified in this
 72 *		list.
 73 *		RCU usage: nodes are not modified in the list of device_opp,
 74 *		however addition is possible and is secured by dev_opp_list_lock
 75 * @dev:	device pointer
 76 * @opp_list:	list of opps
 77 *
 78 * This is an internal data structure maintaining the link to opps attached to
 79 * a device. This structure is not meant to be shared to users as it is
 80 * meant for book keeping and private to OPP library
 81 */
 82struct device_opp {
 83	struct list_head node;
 84
 85	struct device *dev;
 86	struct list_head opp_list;
 87};
 88
 89/*
 90 * The root of the list of all devices. All device_opp structures branch off
 91 * from here, with each device_opp containing the list of opp it supports in
 92 * various states of availability.
 93 */
 94static LIST_HEAD(dev_opp_list);
 95/* Lock to allow exclusive modification to the device and opp lists */
 96static DEFINE_MUTEX(dev_opp_list_lock);
 97
 98/**
 99 * find_device_opp() - find device_opp struct using device pointer
100 * @dev:	device pointer used to lookup device OPPs
101 *
102 * Search list of device OPPs for one containing matching device. Does a RCU
103 * reader operation to grab the pointer needed.
104 *
105 * Returns pointer to 'struct device_opp' if found, otherwise -ENODEV or
106 * -EINVAL based on type of error.
107 *
108 * Locking: This function must be called under rcu_read_lock(). device_opp
109 * is a RCU protected pointer. This means that device_opp is valid as long
110 * as we are under RCU lock.
111 */
112static struct device_opp *find_device_opp(struct device *dev)
113{
114	struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
115
116	if (unlikely(IS_ERR_OR_NULL(dev))) {
117		pr_err("%s: Invalid parameters\n", __func__);
118		return ERR_PTR(-EINVAL);
119	}
120
121	list_for_each_entry_rcu(tmp_dev_opp, &dev_opp_list, node) {
122		if (tmp_dev_opp->dev == dev) {
123			dev_opp = tmp_dev_opp;
124			break;
125		}
126	}
127
128	return dev_opp;
129}
130
131/**
132 * opp_get_voltage() - Gets the voltage corresponding to an available opp
133 * @opp:	opp for which voltage has to be returned for
134 *
135 * Return voltage in micro volt corresponding to the opp, else
136 * return 0
137 *
138 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
139 * protected pointer. This means that opp which could have been fetched by
140 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
141 * under RCU lock. The pointer returned by the opp_find_freq family must be
142 * used in the same section as the usage of this function with the pointer
143 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
144 * pointer.
145 */
146unsigned long opp_get_voltage(struct opp *opp)
147{
148	struct opp *tmp_opp;
149	unsigned long v = 0;
150
151	tmp_opp = rcu_dereference(opp);
152	if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
153		pr_err("%s: Invalid parameters\n", __func__);
154	else
155		v = tmp_opp->u_volt;
156
157	return v;
158}
159
160/**
161 * opp_get_freq() - Gets the frequency corresponding to an available opp
162 * @opp:	opp for which frequency has to be returned for
163 *
164 * Return frequency in hertz corresponding to the opp, else
165 * return 0
166 *
167 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
168 * protected pointer. This means that opp which could have been fetched by
169 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
170 * under RCU lock. The pointer returned by the opp_find_freq family must be
171 * used in the same section as the usage of this function with the pointer
172 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
173 * pointer.
174 */
175unsigned long opp_get_freq(struct opp *opp)
176{
177	struct opp *tmp_opp;
178	unsigned long f = 0;
179
180	tmp_opp = rcu_dereference(opp);
181	if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
182		pr_err("%s: Invalid parameters\n", __func__);
183	else
184		f = tmp_opp->rate;
185
186	return f;
187}
188
189/**
190 * opp_get_opp_count() - Get number of opps available in the opp list
191 * @dev:	device for which we do this operation
192 *
193 * This function returns the number of available opps if there are any,
194 * else returns 0 if none or the corresponding error value.
195 *
196 * Locking: This function must be called under rcu_read_lock(). This function
197 * internally references two RCU protected structures: device_opp and opp which
198 * are safe as long as we are under a common RCU locked section.
199 */
200int opp_get_opp_count(struct device *dev)
201{
202	struct device_opp *dev_opp;
203	struct opp *temp_opp;
204	int count = 0;
205
206	dev_opp = find_device_opp(dev);
207	if (IS_ERR(dev_opp)) {
208		int r = PTR_ERR(dev_opp);
209		dev_err(dev, "%s: device OPP not found (%d)\n", __func__, r);
210		return r;
211	}
212
213	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
214		if (temp_opp->available)
215			count++;
216	}
217
218	return count;
219}
220
221/**
222 * opp_find_freq_exact() - search for an exact frequency
223 * @dev:		device for which we do this operation
224 * @freq:		frequency to search for
225 * @available:		true/false - match for available opp
226 *
227 * Searches for exact match in the opp list and returns pointer to the matching
228 * opp if found, else returns ERR_PTR in case of error and should be handled
229 * using IS_ERR.
230 *
231 * Note: available is a modifier for the search. if available=true, then the
232 * match is for exact matching frequency and is available in the stored OPP
233 * table. if false, the match is for exact frequency which is not available.
234 *
235 * This provides a mechanism to enable an opp which is not available currently
236 * or the opposite as well.
237 *
238 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
239 * protected pointer. The reason for the same is that the opp pointer which is
240 * returned will remain valid for use with opp_get_{voltage, freq} only while
241 * under the locked area. The pointer returned must be used prior to unlocking
242 * with rcu_read_unlock() to maintain the integrity of the pointer.
243 */
244struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
245				bool available)
246{
247	struct device_opp *dev_opp;
248	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
249
250	dev_opp = find_device_opp(dev);
251	if (IS_ERR(dev_opp)) {
252		int r = PTR_ERR(dev_opp);
253		dev_err(dev, "%s: device OPP not found (%d)\n", __func__, r);
254		return ERR_PTR(r);
255	}
256
257	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
258		if (temp_opp->available == available &&
259				temp_opp->rate == freq) {
260			opp = temp_opp;
261			break;
262		}
263	}
264
265	return opp;
266}
267
268/**
269 * opp_find_freq_ceil() - Search for an rounded ceil freq
270 * @dev:	device for which we do this operation
271 * @freq:	Start frequency
272 *
273 * Search for the matching ceil *available* OPP from a starting freq
274 * for a device.
275 *
276 * Returns matching *opp and refreshes *freq accordingly, else returns
277 * ERR_PTR in case of error and should be handled using IS_ERR.
278 *
279 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
280 * protected pointer. The reason for the same is that the opp pointer which is
281 * returned will remain valid for use with opp_get_{voltage, freq} only while
282 * under the locked area. The pointer returned must be used prior to unlocking
283 * with rcu_read_unlock() to maintain the integrity of the pointer.
284 */
285struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
286{
287	struct device_opp *dev_opp;
288	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
289
290	if (!dev || !freq) {
291		dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
292		return ERR_PTR(-EINVAL);
293	}
294
295	dev_opp = find_device_opp(dev);
296	if (IS_ERR(dev_opp))
297		return opp;
298
299	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
300		if (temp_opp->available && temp_opp->rate >= *freq) {
301			opp = temp_opp;
302			*freq = opp->rate;
303			break;
304		}
305	}
306
307	return opp;
308}
309
310/**
311 * opp_find_freq_floor() - Search for a rounded floor freq
312 * @dev:	device for which we do this operation
313 * @freq:	Start frequency
314 *
315 * Search for the matching floor *available* OPP from a starting freq
316 * for a device.
317 *
318 * Returns matching *opp and refreshes *freq accordingly, else returns
319 * ERR_PTR in case of error and should be handled using IS_ERR.
320 *
321 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
322 * protected pointer. The reason for the same is that the opp pointer which is
323 * returned will remain valid for use with opp_get_{voltage, freq} only while
324 * under the locked area. The pointer returned must be used prior to unlocking
325 * with rcu_read_unlock() to maintain the integrity of the pointer.
326 */
327struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
328{
329	struct device_opp *dev_opp;
330	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
331
332	if (!dev || !freq) {
333		dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
334		return ERR_PTR(-EINVAL);
335	}
336
337	dev_opp = find_device_opp(dev);
338	if (IS_ERR(dev_opp))
339		return opp;
340
341	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
342		if (temp_opp->available) {
343			/* go to the next node, before choosing prev */
344			if (temp_opp->rate > *freq)
345				break;
346			else
347				opp = temp_opp;
348		}
349	}
350	if (!IS_ERR(opp))
351		*freq = opp->rate;
352
353	return opp;
354}
355
356/**
357 * opp_add()  - Add an OPP table from a table definitions
358 * @dev:	device for which we do this operation
359 * @freq:	Frequency in Hz for this OPP
360 * @u_volt:	Voltage in uVolts for this OPP
361 *
362 * This function adds an opp definition to the opp list and returns status.
363 * The opp is made available by default and it can be controlled using
364 * opp_enable/disable functions.
365 *
366 * Locking: The internal device_opp and opp structures are RCU protected.
367 * Hence this function internally uses RCU updater strategy with mutex locks
368 * to keep the integrity of the internal data structures. Callers should ensure
369 * that this function is *NOT* called under RCU protection or in contexts where
370 * mutex cannot be locked.
371 */
372int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
373{
374	struct device_opp *dev_opp = NULL;
375	struct opp *opp, *new_opp;
376	struct list_head *head;
377
378	/* allocate new OPP node */
379	new_opp = kzalloc(sizeof(struct opp), GFP_KERNEL);
380	if (!new_opp) {
381		dev_warn(dev, "%s: Unable to create new OPP node\n", __func__);
382		return -ENOMEM;
383	}
384
385	/* Hold our list modification lock here */
386	mutex_lock(&dev_opp_list_lock);
387
388	/* Check for existing list for 'dev' */
389	dev_opp = find_device_opp(dev);
390	if (IS_ERR(dev_opp)) {
391		/*
392		 * Allocate a new device OPP table. In the infrequent case
393		 * where a new device is needed to be added, we pay this
394		 * penalty.
395		 */
396		dev_opp = kzalloc(sizeof(struct device_opp), GFP_KERNEL);
397		if (!dev_opp) {
398			mutex_unlock(&dev_opp_list_lock);
399			kfree(new_opp);
400			dev_warn(dev,
401				"%s: Unable to create device OPP structure\n",
402				__func__);
403			return -ENOMEM;
404		}
405
406		dev_opp->dev = dev;
407		INIT_LIST_HEAD(&dev_opp->opp_list);
408
409		/* Secure the device list modification */
410		list_add_rcu(&dev_opp->node, &dev_opp_list);
411	}
412
413	/* populate the opp table */
414	new_opp->dev_opp = dev_opp;
415	new_opp->rate = freq;
416	new_opp->u_volt = u_volt;
417	new_opp->available = true;
418
419	/* Insert new OPP in order of increasing frequency */
420	head = &dev_opp->opp_list;
421	list_for_each_entry_rcu(opp, &dev_opp->opp_list, node) {
422		if (new_opp->rate < opp->rate)
423			break;
424		else
425			head = &opp->node;
426	}
427
428	list_add_rcu(&new_opp->node, head);
429	mutex_unlock(&dev_opp_list_lock);
430
431	return 0;
432}
433
434/**
435 * opp_set_availability() - helper to set the availability of an opp
436 * @dev:		device for which we do this operation
437 * @freq:		OPP frequency to modify availability
438 * @availability_req:	availability status requested for this opp
439 *
440 * Set the availability of an OPP with an RCU operation, opp_{enable,disable}
441 * share a common logic which is isolated here.
442 *
443 * Returns -EINVAL for bad pointers, -ENOMEM if no memory available for the
444 * copy operation, returns 0 if no modifcation was done OR modification was
445 * successful.
446 *
447 * Locking: The internal device_opp and opp structures are RCU protected.
448 * Hence this function internally uses RCU updater strategy with mutex locks to
449 * keep the integrity of the internal data structures. Callers should ensure
450 * that this function is *NOT* called under RCU protection or in contexts where
451 * mutex locking or synchronize_rcu() blocking calls cannot be used.
452 */
453static int opp_set_availability(struct device *dev, unsigned long freq,
454		bool availability_req)
455{
456	struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
457	struct opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
458	int r = 0;
459
460	/* keep the node allocated */
461	new_opp = kmalloc(sizeof(struct opp), GFP_KERNEL);
462	if (!new_opp) {
463		dev_warn(dev, "%s: Unable to create OPP\n", __func__);
464		return -ENOMEM;
465	}
466
467	mutex_lock(&dev_opp_list_lock);
468
469	/* Find the device_opp */
470	list_for_each_entry(tmp_dev_opp, &dev_opp_list, node) {
471		if (dev == tmp_dev_opp->dev) {
472			dev_opp = tmp_dev_opp;
473			break;
474		}
475	}
476	if (IS_ERR(dev_opp)) {
477		r = PTR_ERR(dev_opp);
478		dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
479		goto unlock;
480	}
481
482	/* Do we have the frequency? */
483	list_for_each_entry(tmp_opp, &dev_opp->opp_list, node) {
484		if (tmp_opp->rate == freq) {
485			opp = tmp_opp;
486			break;
487		}
488	}
489	if (IS_ERR(opp)) {
490		r = PTR_ERR(opp);
491		goto unlock;
492	}
493
494	/* Is update really needed? */
495	if (opp->available == availability_req)
496		goto unlock;
497	/* copy the old data over */
498	*new_opp = *opp;
499
500	/* plug in new node */
501	new_opp->available = availability_req;
502
503	list_replace_rcu(&opp->node, &new_opp->node);
504	mutex_unlock(&dev_opp_list_lock);
505	synchronize_rcu();
506
507	/* clean up old opp */
508	new_opp = opp;
509	goto out;
510
511unlock:
512	mutex_unlock(&dev_opp_list_lock);
513out:
514	kfree(new_opp);
515	return r;
516}
517
518/**
519 * opp_enable() - Enable a specific OPP
520 * @dev:	device for which we do this operation
521 * @freq:	OPP frequency to enable
522 *
523 * Enables a provided opp. If the operation is valid, this returns 0, else the
524 * corresponding error value. It is meant to be used for users an OPP available
525 * after being temporarily made unavailable with opp_disable.
526 *
527 * Locking: The internal device_opp and opp structures are RCU protected.
528 * Hence this function indirectly uses RCU and mutex locks to keep the
529 * integrity of the internal data structures. Callers should ensure that
530 * this function is *NOT* called under RCU protection or in contexts where
531 * mutex locking or synchronize_rcu() blocking calls cannot be used.
532 */
533int opp_enable(struct device *dev, unsigned long freq)
534{
535	return opp_set_availability(dev, freq, true);
536}
537
538/**
539 * opp_disable() - Disable a specific OPP
540 * @dev:	device for which we do this operation
541 * @freq:	OPP frequency to disable
542 *
543 * Disables a provided opp. If the operation is valid, this returns
544 * 0, else the corresponding error value. It is meant to be a temporary
545 * control by users to make this OPP not available until the circumstances are
546 * right to make it available again (with a call to opp_enable).
547 *
548 * Locking: The internal device_opp and opp structures are RCU protected.
549 * Hence this function indirectly uses RCU and mutex locks to keep the
550 * integrity of the internal data structures. Callers should ensure that
551 * this function is *NOT* called under RCU protection or in contexts where
552 * mutex locking or synchronize_rcu() blocking calls cannot be used.
553 */
554int opp_disable(struct device *dev, unsigned long freq)
555{
556	return opp_set_availability(dev, freq, false);
557}
558
559#ifdef CONFIG_CPU_FREQ
560/**
561 * opp_init_cpufreq_table() - create a cpufreq table for a device
562 * @dev:	device for which we do this operation
563 * @table:	Cpufreq table returned back to caller
564 *
565 * Generate a cpufreq table for a provided device- this assumes that the
566 * opp list is already initialized and ready for usage.
567 *
568 * This function allocates required memory for the cpufreq table. It is
569 * expected that the caller does the required maintenance such as freeing
570 * the table as required.
571 *
572 * Returns -EINVAL for bad pointers, -ENODEV if the device is not found, -ENOMEM
573 * if no memory available for the operation (table is not populated), returns 0
574 * if successful and table is populated.
575 *
576 * WARNING: It is  important for the callers to ensure refreshing their copy of
577 * the table if any of the mentioned functions have been invoked in the interim.
578 *
579 * Locking: The internal device_opp and opp structures are RCU protected.
580 * To simplify the logic, we pretend we are updater and hold relevant mutex here
581 * Callers should ensure that this function is *NOT* called under RCU protection
582 * or in contexts where mutex locking cannot be used.
583 */
584int opp_init_cpufreq_table(struct device *dev,
585			    struct cpufreq_frequency_table **table)
586{
587	struct device_opp *dev_opp;
588	struct opp *opp;
589	struct cpufreq_frequency_table *freq_table;
590	int i = 0;
591
592	/* Pretend as if I am an updater */
593	mutex_lock(&dev_opp_list_lock);
594
595	dev_opp = find_device_opp(dev);
596	if (IS_ERR(dev_opp)) {
597		int r = PTR_ERR(dev_opp);
598		mutex_unlock(&dev_opp_list_lock);
599		dev_err(dev, "%s: Device OPP not found (%d)\n", __func__, r);
600		return r;
601	}
602
603	freq_table = kzalloc(sizeof(struct cpufreq_frequency_table) *
604			     (opp_get_opp_count(dev) + 1), GFP_KERNEL);
605	if (!freq_table) {
606		mutex_unlock(&dev_opp_list_lock);
607		dev_warn(dev, "%s: Unable to allocate frequency table\n",
608			__func__);
609		return -ENOMEM;
610	}
611
612	list_for_each_entry(opp, &dev_opp->opp_list, node) {
613		if (opp->available) {
614			freq_table[i].index = i;
615			freq_table[i].frequency = opp->rate / 1000;
616			i++;
617		}
618	}
619	mutex_unlock(&dev_opp_list_lock);
620
621	freq_table[i].index = i;
622	freq_table[i].frequency = CPUFREQ_TABLE_END;
623
624	*table = &freq_table[0];
625
626	return 0;
627}
628
629/**
630 * opp_free_cpufreq_table() - free the cpufreq table
631 * @dev:	device for which we do this operation
632 * @table:	table to free
633 *
634 * Free up the table allocated by opp_init_cpufreq_table
635 */
636void opp_free_cpufreq_table(struct device *dev,
637				struct cpufreq_frequency_table **table)
638{
639	if (!table)
640		return;
641
642	kfree(*table);
643	*table = NULL;
644}
645#endif		/* CONFIG_CPU_FREQ */