--- /dev/null
+// 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(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
+ *
+ * Initialize the object and make sure that we can track locked objects.
+ */
+void drm_exec_init(struct drm_exec *exec, uint32_t flags)
+{
+ exec->flags = flags;
+ exec->objects = kmalloc(PAGE_SIZE, GFP_KERNEL);
+
+ /* If allocation here fails, just delay that till the first use */
+ exec->max_objects = exec->objects ? PAGE_SIZE / sizeof(void *) : 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, 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");
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+#ifndef __DRM_EXEC_H__
+#define __DRM_EXEC_H__
+
+#include <linux/ww_mutex.h>
+
+#define DRM_EXEC_INTERRUPTIBLE_WAIT BIT(0)
+#define DRM_EXEC_IGNORE_DUPLICATES BIT(1)
+
+struct drm_gem_object;
+
+/**
+ * struct drm_exec - Execution context
+ */
+struct drm_exec {
+ /**
+ * @flags: Flags to control locking behavior
+ */
+ uint32_t flags;
+
+ /**
+ * @ticket: WW ticket used for acquiring locks
+ */
+ struct ww_acquire_ctx ticket;
+
+ /**
+ * @num_objects: number of objects locked
+ */
+ unsigned int num_objects;
+
+ /**
+ * @max_objects: maximum objects in array
+ */
+ unsigned int max_objects;
+
+ /**
+ * @objects: array of the locked objects
+ */
+ struct drm_gem_object **objects;
+
+ /**
+ * @contended: contended GEM object we backed off for
+ */
+ struct drm_gem_object *contended;
+
+ /**
+ * @prelocked: already locked GEM object due to contention
+ */
+ struct drm_gem_object *prelocked;
+};
+
+/**
+ * drm_exec_for_each_locked_object - iterate over all the locked objects
+ * @exec: drm_exec object
+ * @index: unsigned long index for the iteration
+ * @obj: the current GEM object
+ *
+ * Iterate over all the locked GEM objects inside the drm_exec object.
+ */
+#define drm_exec_for_each_locked_object(exec, index, obj) \
+ for (index = 0, obj = (exec)->objects[0]; \
+ index < (exec)->num_objects; \
+ ++index, obj = (exec)->objects[index])
+
+/**
+ * drm_exec_until_all_locked - loop until all GEM objects are locked
+ * @exec: drm_exec object
+ *
+ * Core functionality of the drm_exec object. Loops until all GEM objects are
+ * locked and no more contention exists. At the beginning of the loop it is
+ * guaranteed that no GEM object is locked.
+ *
+ * Since labels can't be defined local to the loops body we use a jump pointer
+ * to make sure that the retry is only used from within the loops body.
+ */
+#define drm_exec_until_all_locked(exec) \
+ for (void *__drm_exec_retry_ptr; ({ \
+ __label__ __drm_exec_retry; \
+__drm_exec_retry: \
+ __drm_exec_retry_ptr = &&__drm_exec_retry; \
+ (void)__drm_exec_retry_ptr; \
+ drm_exec_cleanup(exec); \
+ });)
+
+/**
+ * drm_exec_retry_on_contention - restart the loop to grap all locks
+ * @exec: drm_exec object
+ *
+ * Control flow helper to continue when a contention was detected and we need to
+ * clean up and re-start the loop to prepare all GEM objects.
+ */
+#define drm_exec_retry_on_contention(exec) \
+ do { \
+ if (unlikely(drm_exec_is_contended(exec))) \
+ goto *__drm_exec_retry_ptr; \
+ } while (0)
+
+/**
+ * drm_exec_is_contended - check for contention
+ * @exec: drm_exec object
+ *
+ * Returns true if the drm_exec object has run into some contention while
+ * locking a GEM object and needs to clean up.
+ */
+static inline bool drm_exec_is_contended(struct drm_exec *exec)
+{
+ return !!exec->contended;
+}
+
+void drm_exec_init(struct drm_exec *exec, uint32_t flags);
+void drm_exec_fini(struct drm_exec *exec);
+bool drm_exec_cleanup(struct drm_exec *exec);
+int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
+void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj);
+int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
+ unsigned int num_fences);
+int drm_exec_prepare_array(struct drm_exec *exec,
+ struct drm_gem_object **objects,
+ unsigned int num_objects,
+ unsigned int num_fences);
+
+#endif
projects / linux-platform-drivers-x86.git / commitdiff