1/*
  2 * Copyright (C) 2014 Red Hat
  3 * Author: Rob Clark <robdclark@gmail.com>
  4 *
  5 * Permission is hereby granted, free of charge, to any person obtaining a
  6 * copy of this software and associated documentation files (the "Software"),
  7 * to deal in the Software without restriction, including without limitation
  8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  9 * and/or sell copies of the Software, and to permit persons to whom the
 10 * Software is furnished to do so, subject to the following conditions:
 11 *
 12 * The above copyright notice and this permission notice shall be included in
 13 * all copies or substantial portions of the Software.
 14 *
 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 18 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 21 * OTHER DEALINGS IN THE SOFTWARE.
 22 */
 23
 24#ifndef DRM_MODESET_LOCK_H_
 25#define DRM_MODESET_LOCK_H_
 26
 27#include <linux/ww_mutex.h>
 28
 29struct drm_modeset_lock;
 30
 31/**
 32 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx)
 33 * @ww_ctx: base acquire ctx
 34 * @contended: used internally for -EDEADLK handling
 35 * @locked: list of held locks
 36 * @trylock_only: trylock mode used in atomic contexts/panic notifiers
 37 * @interruptible: whether interruptible locking should be used.
 38 *
 39 * Each thread competing for a set of locks must use one acquire
 40 * ctx.  And if any lock fxn returns -EDEADLK, it must backoff and
 41 * retry.
 42 */
 43struct drm_modeset_acquire_ctx {
 44
 45	struct ww_acquire_ctx ww_ctx;
 46
 47	/*
 48	 * Contended lock: if a lock is contended you should only call
 49	 * drm_modeset_backoff() which drops locks and slow-locks the
 50	 * contended lock.
 51	 */
 52	struct drm_modeset_lock *contended;
 53
 54	/*
 55	 * list of held locks (drm_modeset_lock)
 56	 */
 57	struct list_head locked;
 58
 59	/*
 60	 * Trylock mode, use only for panic handlers!
 61	 */
 62	bool trylock_only;
 63
 64	/* Perform interruptible waits on this context. */
 65	bool interruptible;
 66};
 67
 68/**
 69 * struct drm_modeset_lock - used for locking modeset resources.
 70 * @mutex: resource locking
 71 * @head: used to hold its place on &drm_atomi_state.locked list when
 72 *    part of an atomic update
 73 *
 74 * Used for locking CRTCs and other modeset resources.
 75 */
 76struct drm_modeset_lock {
 77	/*
 78	 * modeset lock
 79	 */
 80	struct ww_mutex mutex;
 81
 82	/*
 83	 * Resources that are locked as part of an atomic update are added
 84	 * to a list (so we know what to unlock at the end).
 85	 */
 86	struct list_head head;
 87};
 88
 89#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)
 90
 91void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
 92		uint32_t flags);
 93void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
 94void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);
 95int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);
 96
 97void drm_modeset_lock_init(struct drm_modeset_lock *lock);
 98
 99/**
100 * drm_modeset_lock_fini - cleanup lock
101 * @lock: lock to cleanup
102 */
103static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock)
104{
105	WARN_ON(!list_empty(&lock->head));
106}
107
108/**
109 * drm_modeset_is_locked - equivalent to mutex_is_locked()
110 * @lock: lock to check
111 */
112static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
113{
114	return ww_mutex_is_locked(&lock->mutex);
115}
116
117/**
118 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held()
119 * @lock: lock to check
120 */
121static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock)
122{
123	lockdep_assert_held(&lock->mutex.base);
124}
125
126int drm_modeset_lock(struct drm_modeset_lock *lock,
127		struct drm_modeset_acquire_ctx *ctx);
128int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
129void drm_modeset_unlock(struct drm_modeset_lock *lock);
130
131struct drm_device;
132struct drm_crtc;
133struct drm_plane;
134
135void drm_modeset_lock_all(struct drm_device *dev);
136void drm_modeset_unlock_all(struct drm_device *dev);
137void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);
138
139int drm_modeset_lock_all_ctx(struct drm_device *dev,
140			     struct drm_modeset_acquire_ctx *ctx);
141
142/**
143 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
144 * @dev: drm device
145 * @ctx: local modeset acquire context, will be dereferenced
146 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
147 * @ret: local ret/err/etc variable to track error status
148 *
149 * Use these macros to simplify grabbing all modeset locks using a local
150 * context. This has the advantage of reducing boilerplate, but also properly
151 * checking return values where appropriate.
152 *
153 * Any code run between BEGIN and END will be holding the modeset locks.
154 *
155 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
156 * forth between the labels on deadlock and error conditions.
157 *
158 * Drivers can acquire additional modeset locks. If any lock acquisition
159 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
160 * the @ret parameter containing the return value of drm_modeset_lock().
161 *
162 * Returns:
163 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
164 * is 0, so no error checking is necessary
165 */
166#define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret)		\
167	if (!drm_drv_uses_atomic_modeset(dev))				\
168		mutex_lock(&dev->mode_config.mutex);			\
169	drm_modeset_acquire_init(&ctx, flags);				\
170modeset_lock_retry:							\
171	ret = drm_modeset_lock_all_ctx(dev, &ctx);			\
172	if (ret)							\
173		goto modeset_lock_fail;
174
175/**
176 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
177 * @dev: drm device
178 * @ctx: local modeset acquire context, will be dereferenced
179 * @ret: local ret/err/etc variable to track error status
180 *
181 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
182 * if ret is -EDEADLK.
183 *
184 * It's important that you use the same ret variable for begin and end so
185 * deadlock conditions are properly handled.
186 *
187 * Returns:
188 * ret will be untouched unless it is -EDEADLK on entry. That means that if you
189 * successfully acquire the locks, ret will be whatever your code sets it to. If
190 * there is a deadlock or other failure with acquire or backoff, ret will be set
191 * to that failure. In both of these cases the code between BEGIN/END will not
192 * be run, so the failure will reflect the inability to grab the locks.
193 */
194#define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret)				\
195modeset_lock_fail:							\
196	if (ret == -EDEADLK) {						\
197		ret = drm_modeset_backoff(&ctx);			\
198		if (!ret)						\
199			goto modeset_lock_retry;			\
200	}								\
201	drm_modeset_drop_locks(&ctx);					\
202	drm_modeset_acquire_fini(&ctx);					\
203	if (!drm_drv_uses_atomic_modeset(dev))				\
204		mutex_unlock(&dev->mode_config.mutex);
205
206#endif /* DRM_MODESET_LOCK_H_ */