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/* |
* Fence mechanism for dma-buf to allow for asynchronous dma access |
* |
* Copyright (C) 2012 Canonical Ltd |
* Copyright (C) 2012 Texas Instruments |
* |
* Authors: |
* Rob Clark <robdclark@gmail.com> |
* Maarten Lankhorst <maarten.lankhorst@canonical.com> |
* |
* This program is free software; you can redistribute it and/or modify it |
* under the terms of the GNU General Public License version 2 as published by |
* the Free Software Foundation. |
* |
* This program is distributed in the hope that it will be useful, but WITHOUT |
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
* more details. |
*/ |
|
#ifndef __LINUX_FENCE_H |
#define __LINUX_FENCE_H |
|
#include <linux/err.h> |
#include <linux/wait.h> |
#include <linux/list.h> |
#include <linux/bitops.h> |
#include <linux/kref.h> |
#include <linux/sched.h> |
#include <linux/printk.h> |
#include <linux/rcupdate.h> |
|
struct fence; |
struct fence_ops; |
struct fence_cb; |
|
/** |
* struct fence - software synchronization primitive |
* @refcount: refcount for this fence |
* @ops: fence_ops associated with this fence |
* @rcu: used for releasing fence with kfree_rcu |
* @cb_list: list of all callbacks to call |
* @lock: spin_lock_irqsave used for locking |
* @context: execution context this fence belongs to, returned by |
* fence_context_alloc() |
* @seqno: the sequence number of this fence inside the execution context, |
* can be compared to decide which fence would be signaled later. |
* @flags: A mask of FENCE_FLAG_* defined below |
* @timestamp: Timestamp when the fence was signaled. |
* @status: Optional, only valid if < 0, must be set before calling |
* fence_signal, indicates that the fence has completed with an error. |
* |
* the flags member must be manipulated and read using the appropriate |
* atomic ops (bit_*), so taking the spinlock will not be needed most |
* of the time. |
* |
* FENCE_FLAG_SIGNALED_BIT - fence is already signaled |
* FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called* |
* FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the |
* implementer of the fence for its own purposes. Can be used in different |
* ways by different fence implementers, so do not rely on this. |
* |
* *) Since atomic bitops are used, this is not guaranteed to be the case. |
* Particularly, if the bit was set, but fence_signal was called right |
* before this bit was set, it would have been able to set the |
* FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called. |
* Adding a check for FENCE_FLAG_SIGNALED_BIT after setting |
* FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that |
* after fence_signal was called, any enable_signaling call will have either |
* been completed, or never called at all. |
*/ |
struct fence { |
struct kref refcount; |
const struct fence_ops *ops; |
struct rcu_head rcu; |
struct list_head cb_list; |
spinlock_t *lock; |
unsigned context, seqno; |
unsigned long flags; |
// ktime_t timestamp; |
int status; |
}; |
|
enum fence_flag_bits { |
FENCE_FLAG_SIGNALED_BIT, |
FENCE_FLAG_ENABLE_SIGNAL_BIT, |
FENCE_FLAG_USER_BITS, /* must always be last member */ |
}; |
|
typedef void (*fence_func_t)(struct fence *fence, struct fence_cb *cb); |
|
/** |
* struct fence_cb - callback for fence_add_callback |
* @node: used by fence_add_callback to append this struct to fence::cb_list |
* @func: fence_func_t to call |
* |
* This struct will be initialized by fence_add_callback, additional |
* data can be passed along by embedding fence_cb in another struct. |
*/ |
struct fence_cb { |
struct list_head node; |
fence_func_t func; |
}; |
|
/** |
* struct fence_ops - operations implemented for fence |
* @get_driver_name: returns the driver name. |
* @get_timeline_name: return the name of the context this fence belongs to. |
* @enable_signaling: enable software signaling of fence. |
* @signaled: [optional] peek whether the fence is signaled, can be null. |
* @wait: custom wait implementation, or fence_default_wait. |
* @release: [optional] called on destruction of fence, can be null |
* @fill_driver_data: [optional] callback to fill in free-form debug info |
* Returns amount of bytes filled, or -errno. |
* @fence_value_str: [optional] fills in the value of the fence as a string |
* @timeline_value_str: [optional] fills in the current value of the timeline |
* as a string |
* |
* Notes on enable_signaling: |
* For fence implementations that have the capability for hw->hw |
* signaling, they can implement this op to enable the necessary |
* irqs, or insert commands into cmdstream, etc. This is called |
* in the first wait() or add_callback() path to let the fence |
* implementation know that there is another driver waiting on |
* the signal (ie. hw->sw case). |
* |
* This function can be called called from atomic context, but not |
* from irq context, so normal spinlocks can be used. |
* |
* A return value of false indicates the fence already passed, |
* or some failure occurred that made it impossible to enable |
* signaling. True indicates successful enabling. |
* |
* fence->status may be set in enable_signaling, but only when false is |
* returned. |
* |
* Calling fence_signal before enable_signaling is called allows |
* for a tiny race window in which enable_signaling is called during, |
* before, or after fence_signal. To fight this, it is recommended |
* that before enable_signaling returns true an extra reference is |
* taken on the fence, to be released when the fence is signaled. |
* This will mean fence_signal will still be called twice, but |
* the second time will be a noop since it was already signaled. |
* |
* Notes on signaled: |
* May set fence->status if returning true. |
* |
* Notes on wait: |
* Must not be NULL, set to fence_default_wait for default implementation. |
* the fence_default_wait implementation should work for any fence, as long |
* as enable_signaling works correctly. |
* |
* Must return -ERESTARTSYS if the wait is intr = true and the wait was |
* interrupted, and remaining jiffies if fence has signaled, or 0 if wait |
* timed out. Can also return other error values on custom implementations, |
* which should be treated as if the fence is signaled. For example a hardware |
* lockup could be reported like that. |
* |
* Notes on release: |
* Can be NULL, this function allows additional commands to run on |
* destruction of the fence. Can be called from irq context. |
* If pointer is set to NULL, kfree will get called instead. |
*/ |
|
struct fence_ops { |
const char * (*get_driver_name)(struct fence *fence); |
const char * (*get_timeline_name)(struct fence *fence); |
bool (*enable_signaling)(struct fence *fence); |
bool (*signaled)(struct fence *fence); |
signed long (*wait)(struct fence *fence, bool intr, signed long timeout); |
void (*release)(struct fence *fence); |
|
int (*fill_driver_data)(struct fence *fence, void *data, int size); |
void (*fence_value_str)(struct fence *fence, char *str, int size); |
void (*timeline_value_str)(struct fence *fence, char *str, int size); |
}; |
|
void fence_init(struct fence *fence, const struct fence_ops *ops, |
spinlock_t *lock, unsigned context, unsigned seqno); |
|
void fence_release(struct kref *kref); |
void fence_free(struct fence *fence); |
|
/** |
* fence_get - increases refcount of the fence |
* @fence: [in] fence to increase refcount of |
* |
* Returns the same fence, with refcount increased by 1. |
*/ |
static inline struct fence *fence_get(struct fence *fence) |
{ |
if (fence) |
kref_get(&fence->refcount); |
return fence; |
} |
|
/** |
* fence_get_rcu - get a fence from a reservation_object_list with rcu read lock |
* @fence: [in] fence to increase refcount of |
* |
* Function returns NULL if no refcount could be obtained, or the fence. |
*/ |
static inline struct fence *fence_get_rcu(struct fence *fence) |
{ |
if (kref_get_unless_zero(&fence->refcount)) |
return fence; |
else |
return NULL; |
} |
|
/** |
* fence_put - decreases refcount of the fence |
* @fence: [in] fence to reduce refcount of |
*/ |
static inline void fence_put(struct fence *fence) |
{ |
if (fence) |
kref_put(&fence->refcount, fence_release); |
} |
|
int fence_signal(struct fence *fence); |
int fence_signal_locked(struct fence *fence); |
signed long fence_default_wait(struct fence *fence, bool intr, signed long timeout); |
int fence_add_callback(struct fence *fence, struct fence_cb *cb, |
fence_func_t func); |
bool fence_remove_callback(struct fence *fence, struct fence_cb *cb); |
void fence_enable_sw_signaling(struct fence *fence); |
|
/** |
* fence_is_signaled_locked - Return an indication if the fence is signaled yet. |
* @fence: [in] the fence to check |
* |
* Returns true if the fence was already signaled, false if not. Since this |
* function doesn't enable signaling, it is not guaranteed to ever return |
* true if fence_add_callback, fence_wait or fence_enable_sw_signaling |
* haven't been called before. |
* |
* This function requires fence->lock to be held. |
*/ |
static inline bool |
fence_is_signaled_locked(struct fence *fence) |
{ |
if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) |
return true; |
|
if (fence->ops->signaled && fence->ops->signaled(fence)) { |
fence_signal_locked(fence); |
return true; |
} |
|
return false; |
} |
|
/** |
* fence_is_signaled - Return an indication if the fence is signaled yet. |
* @fence: [in] the fence to check |
* |
* Returns true if the fence was already signaled, false if not. Since this |
* function doesn't enable signaling, it is not guaranteed to ever return |
* true if fence_add_callback, fence_wait or fence_enable_sw_signaling |
* haven't been called before. |
* |
* It's recommended for seqno fences to call fence_signal when the |
* operation is complete, it makes it possible to prevent issues from |
* wraparound between time of issue and time of use by checking the return |
* value of this function before calling hardware-specific wait instructions. |
*/ |
static inline bool |
fence_is_signaled(struct fence *fence) |
{ |
if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) |
return true; |
|
if (fence->ops->signaled && fence->ops->signaled(fence)) { |
fence_signal(fence); |
return true; |
} |
|
return false; |
} |
|
/** |
* fence_later - return the chronologically later fence |
* @f1: [in] the first fence from the same context |
* @f2: [in] the second fence from the same context |
* |
* Returns NULL if both fences are signaled, otherwise the fence that would be |
* signaled last. Both fences must be from the same context, since a seqno is |
* not re-used across contexts. |
*/ |
static inline struct fence *fence_later(struct fence *f1, struct fence *f2) |
{ |
if (WARN_ON(f1->context != f2->context)) |
return NULL; |
|
/* |
* can't check just FENCE_FLAG_SIGNALED_BIT here, it may never have been |
* set if enable_signaling wasn't called, and enabling that here is |
* overkill. |
*/ |
if (f2->seqno - f1->seqno <= INT_MAX) |
return fence_is_signaled(f2) ? NULL : f2; |
else |
return fence_is_signaled(f1) ? NULL : f1; |
} |
|
signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout); |
|
|
/** |
* fence_wait - sleep until the fence gets signaled |
* @fence: [in] the fence to wait on |
* @intr: [in] if true, do an interruptible wait |
* |
* This function will return -ERESTARTSYS if interrupted by a signal, |
* or 0 if the fence was signaled. Other error values may be |
* returned on custom implementations. |
* |
* Performs a synchronous wait on this fence. It is assumed the caller |
* directly or indirectly holds a reference to the fence, otherwise the |
* fence might be freed before return, resulting in undefined behavior. |
*/ |
static inline signed long fence_wait(struct fence *fence, bool intr) |
{ |
signed long ret; |
|
/* Since fence_wait_timeout cannot timeout with |
* MAX_SCHEDULE_TIMEOUT, only valid return values are |
* -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT. |
*/ |
ret = fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT); |
|
return ret < 0 ? ret : 0; |
} |
|
unsigned fence_context_alloc(unsigned num); |
|
#define FENCE_TRACE(f, fmt, args...) \ |
do { \ |
struct fence *__ff = (f); \ |
} while (0) |
|
#define FENCE_WARN(f, fmt, args...) \ |
do { \ |
struct fence *__ff = (f); \ |
pr_warn("f %u#%u: " fmt, __ff->context, __ff->seqno, \ |
##args); \ |
} while (0) |
|
#define FENCE_ERR(f, fmt, args...) \ |
do { \ |
struct fence *__ff = (f); \ |
pr_err("f %u#%u: " fmt, __ff->context, __ff->seqno, \ |
##args); \ |
} while (0) |
|
#endif /* __LINUX_FENCE_H */ |