// SPDX-License-Identifier: GPL-2.0 OR MIT
#include <drm/drm_exec.h>
#include <drm/drm_gem.h>
#include <linux/dma-resv.h>
/**
* DOC: Overview
*
* This component mainly abstracts the retry loop necessary for locking
* multiple GEM objects while preparing hardware operations (e.g. command
* submissions, page table updates etc..).
*
* If a contention is detected while locking a GEM object the cleanup procedure
* unlocks all previously locked GEM objects and locks the contended one first
* before locking any further objects.
*
* After an object is locked fences slots can optionally be reserved on the
* dma_resv object inside the GEM object.
*
* A typical usage pattern should look like this::
*
* struct drm_gem_object *obj;
* struct drm_exec exec;
* unsigned long index;
* int ret;
*
* drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
* drm_exec_until_all_locked(&exec) {
* ret = drm_exec_prepare_obj(&exec, boA, 1);
* drm_exec_retry_on_contention(&exec);
* if (ret)
* goto error;
*
* ret = drm_exec_prepare_obj(&exec, boB, 1);
* drm_exec_retry_on_contention(&exec);
* if (ret)
* goto error;
* }
*
* drm_exec_for_each_locked_object(&exec, index, obj) {
* dma_resv_add_fence(obj->resv, fence, DMA_RESV_USAGE_READ);
* ...
* }
* drm_exec_fini(&exec);
*
* See struct dma_exec for more details.
*/
/* Dummy value used to initially enter the retry loop */
#define DRM_EXEC_DUMMY ((void *)~0)
/* Unlock all objects and drop references */
static void drm_exec_unlock_all(struct drm_exec *exec)
{
struct drm_gem_object *obj;
unsigned long index;
drm_exec_for_each_locked_object_reverse(exec, index, obj) {
dma_resv_unlock(obj->resv);
drm_gem_object_put(obj);
}
drm_gem_object_put(exec->prelocked);
exec->prelocked = NULL;
}
/**
* drm_exec_init - initialize a drm_exec object
* @exec: the drm_exec object to initialize
* @flags: controls locking behavior, see DRM_EXEC_* defines
* @nr: the initial # of objects
*
* Initialize the object and make sure that we can track locked objects.
*
* If nr is non-zero then it is used as the initial objects table size.
* In either case, the table will grow (be re-allocated) on demand.
*/
void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr)
{
if (!nr)
nr = PAGE_SIZE / sizeof(void *);
exec->flags = flags;
exec->objects = kvmalloc_array(nr, sizeof(void *), GFP_KERNEL);
/* If allocation here fails, just delay that till the first use */
exec->max_objects = exec->objects ? nr : 0;
exec->num_objects = 0;
exec->contended = DRM_EXEC_DUMMY;
exec->prelocked = NULL;
}
EXPORT_SYMBOL(drm_exec_init);
/**
* drm_exec_fini - finalize a drm_exec object
* @exec: the drm_exec object to finalize
*
* Unlock all locked objects, drop the references to objects and free all memory
* used for tracking the state.
*/
void drm_exec_fini(struct drm_exec *exec)
{
drm_exec_unlock_all(exec);
kvfree(exec->objects);
if (exec->contended != DRM_EXEC_DUMMY) {
drm_gem_object_put(exec->contended);
ww_acquire_fini(&exec->ticket);
}
}
EXPORT_SYMBOL(drm_exec_fini);
/**
* drm_exec_cleanup - cleanup when contention is detected
* @exec: the drm_exec object to cleanup
*
* Cleanup the current state and return true if we should stay inside the retry
* loop, false if there wasn't any contention detected and we can keep the
* objects locked.
*/
bool drm_exec_cleanup(struct drm_exec *exec)
{
if (likely(!exec->contended)) {
ww_acquire_done(&exec->ticket);
return false;
}
if (likely(exec->contended == DRM_EXEC_DUMMY)) {
exec->contended = NULL;
ww_acquire_init(&exec->ticket, &reservation_ww_class);
return true;
}
drm_exec_unlock_all(exec);
exec->num_objects = 0;
return true;
}
EXPORT_SYMBOL(drm_exec_cleanup);
/* Track the locked object in the array */
static int drm_exec_obj_locked(struct drm_exec *exec,
struct drm_gem_object *obj)
{
if (unlikely(exec->num_objects == exec->max_objects)) {
size_t size = exec->max_objects * sizeof(void *);
void *tmp;
tmp = kvrealloc(exec->objects, size + PAGE_SIZE, GFP_KERNEL);
if (!tmp)
return -ENOMEM;
exec->objects = tmp;
exec->max_objects += PAGE_SIZE / sizeof(void *);
}
drm_gem_object_get(obj);
exec->objects[exec->num_objects++] = obj;
return 0;
}
/* Make sure the contended object is locked first */
static int drm_exec_lock_contended(struct drm_exec *exec)
{
struct drm_gem_object *obj = exec->contended;
int ret;
if (likely(!obj))
return 0;
/* Always cleanup the contention so that error handling can kick in */
exec->contended = NULL;
if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) {
ret = dma_resv_lock_slow_interruptible(obj->resv,
&exec->ticket);
if (unlikely(ret))
goto error_dropref;
} else {
dma_resv_lock_slow(obj->resv, &exec->ticket);
}
ret = drm_exec_obj_locked(exec, obj);
if (unlikely(ret))
goto error_unlock;
exec->prelocked = obj;
return 0;
error_unlock:
dma_resv_unlock(obj->resv);
error_dropref:
drm_gem_object_put(obj);
return ret;
}
/**
* drm_exec_lock_obj - lock a GEM object for use
* @exec: the drm_exec object with the state
* @obj: the GEM object to lock
*
* Lock a GEM object for use and grab a reference to it.
*
* Returns: -EDEADLK if a contention is detected, -EALREADY when object is
* already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES
* flag), -ENOMEM when memory allocation failed and zero for success.
*/
int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
{
int ret;
ret = drm_exec_lock_contended(exec);
if (unlikely(ret))
return ret;
if (exec->prelocked == obj) {
drm_gem_object_put(exec->prelocked);
exec->prelocked = NULL;
return 0;
}
if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT)
ret = dma_resv_lock_interruptible(obj->resv, &exec->ticket);
else
ret = dma_resv_lock(obj->resv, &exec->ticket);
if (unlikely(ret == -EDEADLK)) {
drm_gem_object_get(obj);
exec->contended = obj;
return -EDEADLK;
}
if (unlikely(ret == -EALREADY) &&
exec->flags & DRM_EXEC_IGNORE_DUPLICATES)
return 0;
if (unlikely(ret))
return ret;
ret = drm_exec_obj_locked(exec, obj);
if (ret)
goto error_unlock;
return 0;
error_unlock:
dma_resv_unlock(obj->resv);
return ret;
}
EXPORT_SYMBOL(drm_exec_lock_obj);
/**
* drm_exec_unlock_obj - unlock a GEM object in this exec context
* @exec: the drm_exec object with the state
* @obj: the GEM object to unlock
*
* Unlock the GEM object and remove it from the collection of locked objects.
* Should only be used to unlock the most recently locked objects. It's not time
* efficient to unlock objects locked long ago.
*/
void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
{
unsigned int i;
for (i = exec->num_objects; i--;) {
if (exec->objects[i] == obj) {
dma_resv_unlock(obj->resv);
for (++i; i < exec->num_objects; ++i)
exec->objects[i - 1] = exec->objects[i];
--exec->num_objects;
drm_gem_object_put(obj);
return;
}
}
}
EXPORT_SYMBOL(drm_exec_unlock_obj);
/**
* drm_exec_prepare_obj - prepare a GEM object for use
* @exec: the drm_exec object with the state
* @obj: the GEM object to prepare
* @num_fences: how many fences to reserve
*
* Prepare a GEM object for use by locking it and reserving fence slots.
*
* Returns: -EDEADLK if a contention is detected, -EALREADY when object is
* already locked, -ENOMEM when memory allocation failed and zero for success.
*/
int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
unsigned int num_fences)
{
int ret;
ret = drm_exec_lock_obj(exec, obj);
if (ret)
return ret;
ret = dma_resv_reserve_fences(obj->resv, num_fences);
if (ret) {
drm_exec_unlock_obj(exec, obj);
return ret;
}
return 0;
}
EXPORT_SYMBOL(drm_exec_prepare_obj);
/**
* drm_exec_prepare_array - helper to prepare an array of objects
* @exec: the drm_exec object with the state
* @objects: array of GEM object to prepare
* @num_objects: number of GEM objects in the array
* @num_fences: number of fences to reserve on each GEM object
*
* Prepares all GEM objects in an array, aborts on first error.
* Reserves @num_fences on each GEM object after locking it.
*
* Returns: -EDEADLOCK on contention, -EALREADY when object is already locked,
* -ENOMEM when memory allocation failed and zero for success.
*/
int drm_exec_prepare_array(struct drm_exec *exec,
struct drm_gem_object **objects,
unsigned int num_objects,
unsigned int num_fences)
{
int ret;
for (unsigned int i = 0; i < num_objects; ++i) {
ret = drm_exec_prepare_obj(exec, objects[i], num_fences);
if (unlikely(ret))
return ret;
}
return 0;
}
EXPORT_SYMBOL(drm_exec_prepare_array);
MODULE_DESCRIPTION("DRM execution context");
MODULE_LICENSE("Dual MIT/GPL");
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