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drm/i915/ttm: Embed a ttm buffer object in the i915 gem object 

Embed a struct ttm_buffer_object into the i915 gem object, making sure
we alias the gem object part. It's a bit unfortunate that the
struct ttm_buffer_ojbect embeds a gem object since we otherwise could
make the TTM part private to the TTM backend, and use the usual
i915 gem object for the other backends.
To make this a bit more storage efficient for the other backends,
we'd have to use a pointer for the gem object which would require
a lot of changes in the driver. We postpone that for later.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210602083818.241793-3-thomas.hellstrom@linux.intel.com
This commit is contained in:
Thomas Hellström 2021-06-02 10:38:09 +02:00 committed by Matthew Auld
parent d148738923
commit f4db23f2c0
2 changed files with 18 additions and 1 deletions
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7
drivers/gpu/drm/i915/gem/i915_gem_object.c
View File

@ -62,6 +62,13 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
const struct drm_i915_gem_object_ops *ops,
struct lock_class_key *key, unsigned flags)
{
/*
* A gem object is embedded both in a struct ttm_buffer_object :/ and
* in a drm_i915_gem_object. Make sure they are aliased.
*/
BUILD_BUG_ON(offsetof(typeof(*obj), base) !=
offsetof(typeof(*obj), __do_not_access.base));
spin_lock_init(&obj->vma.lock);
INIT_LIST_HEAD(&obj->vma.list);

12
drivers/gpu/drm/i915/gem/i915_gem_object_types.h
View File

@ -10,6 +10,7 @@
#include <linux/mmu_notifier.h>
#include <drm/drm_gem.h>
#include <drm/ttm/ttm_bo_api.h>
#include <uapi/drm/i915_drm.h>
#include "i915_active.h"
@ -99,7 +100,16 @@ struct i915_gem_object_page_iter {
};
struct drm_i915_gem_object {
struct drm_gem_object base;
/*
* We might have reason to revisit the below since it wastes
* a lot of space for non-ttm gem objects.
* In any case, always use the accessors for the ttm_buffer_object
* when accessing it.
*/
union {
struct drm_gem_object base;
struct ttm_buffer_object __do_not_access;
};
const struct drm_i915_gem_object_ops *ops;