The kmap and kunmap operations of GEM VRAM buffers can now be called in interleaving pairs. The first call to drm_gem_vram_kmap() maps the buffer's memory to kernel address space and the final call to drm_gem_vram_kunmap() unmaps the memory. Intermediate calls to these functions increment or decrement a reference counter.
This change allows for keeping buffer memory mapped for longer and minimizes the amount of changes to TLB, page tables, etc.
v4: * lock in kmap()/kunmap() with ttm_bo_reserve()
Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Gerd Hoffmann kraxel@redhat.com Cc: Davidlohr Bueso dave@stgolabs.net --- drivers/gpu/drm/drm_gem_vram_helper.c | 75 ++++++++++++++++++++------- include/drm/drm_gem_vram_helper.h | 14 +++++ 2 files changed, 71 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c index fd751078bae1..5e86ec06644b 100644 --- a/drivers/gpu/drm/drm_gem_vram_helper.c +++ b/drivers/gpu/drm/drm_gem_vram_helper.c @@ -26,6 +26,9 @@ static void drm_gem_vram_cleanup(struct drm_gem_vram_object *gbo) * TTM buffer object in 'bo' has already been cleaned * up; only release the GEM object. */ + + WARN_ON(gbo->kmap_use_count); + drm_gem_object_release(&gbo->bo.base); }
@@ -283,6 +286,34 @@ int drm_gem_vram_unpin(struct drm_gem_vram_object *gbo) } EXPORT_SYMBOL(drm_gem_vram_unpin);
+static void *drm_gem_vram_kmap_locked(struct drm_gem_vram_object *gbo, + bool map, bool *is_iomem) +{ + int ret; + struct ttm_bo_kmap_obj *kmap = &gbo->kmap; + + if (gbo->kmap_use_count > 0) + goto out; + + if (kmap->virtual || !map) + goto out; + + ret = ttm_bo_kmap(&gbo->bo, 0, gbo->bo.num_pages, kmap); + if (ret) + return ERR_PTR(ret); + +out: + if (!kmap->virtual) { + if (is_iomem) + *is_iomem = false; + return NULL; /* not mapped; don't increment ref */ + } + ++gbo->kmap_use_count; + if (is_iomem) + return ttm_kmap_obj_virtual(kmap, is_iomem); + return kmap->virtual; +} + /** * drm_gem_vram_kmap() - Maps a GEM VRAM object into kernel address space * @gbo: the GEM VRAM object @@ -304,40 +335,48 @@ void *drm_gem_vram_kmap(struct drm_gem_vram_object *gbo, bool map, bool *is_iomem) { int ret; - struct ttm_bo_kmap_obj *kmap = &gbo->kmap; - - if (kmap->virtual || !map) - goto out; + void *virtual;
- ret = ttm_bo_kmap(&gbo->bo, 0, gbo->bo.num_pages, kmap); + ret = ttm_bo_reserve(&gbo->bo, true, false, NULL); if (ret) return ERR_PTR(ret); + virtual = drm_gem_vram_kmap_locked(gbo, map, is_iomem); + ttm_bo_unreserve(&gbo->bo);
-out: - if (!is_iomem) - return kmap->virtual; - if (!kmap->virtual) { - *is_iomem = false; - return NULL; - } - return ttm_kmap_obj_virtual(kmap, is_iomem); + return virtual; } EXPORT_SYMBOL(drm_gem_vram_kmap);
-/** - * drm_gem_vram_kunmap() - Unmaps a GEM VRAM object - * @gbo: the GEM VRAM object - */ -void drm_gem_vram_kunmap(struct drm_gem_vram_object *gbo) +static void drm_gem_vram_kunmap_locked(struct drm_gem_vram_object *gbo) { struct ttm_bo_kmap_obj *kmap = &gbo->kmap;
+ if (WARN_ON_ONCE(!gbo->kmap_use_count)) + return; + if (--gbo->kmap_use_count > 0) + return; + if (!kmap->virtual) return;
ttm_bo_kunmap(kmap); kmap->virtual = NULL; } + +/** + * drm_gem_vram_kunmap() - Unmaps a GEM VRAM object + * @gbo: the GEM VRAM object + */ +void drm_gem_vram_kunmap(struct drm_gem_vram_object *gbo) +{ + int ret; + + ret = ttm_bo_reserve(&gbo->bo, false, false, NULL); + if (WARN_ONCE(ret, "ttm_bo_reserve_failed(): ret=%d\n", ret)) + return; + drm_gem_vram_kunmap_locked(gbo); + ttm_bo_unreserve(&gbo->bo); +} EXPORT_SYMBOL(drm_gem_vram_kunmap);
/** diff --git a/include/drm/drm_gem_vram_helper.h b/include/drm/drm_gem_vram_helper.h index ac217d768456..4f0e207ee097 100644 --- a/include/drm/drm_gem_vram_helper.h +++ b/include/drm/drm_gem_vram_helper.h @@ -34,11 +34,25 @@ struct vm_area_struct; * backed by VRAM. It can be used for simple framebuffer devices with * dedicated memory. The buffer object can be evicted to system memory if * video memory becomes scarce. + * + * GEM VRAM objects perform reference counting for pin and mapping + * operations. So a buffer object that has been pinned N times with + * drm_gem_vram_pin() must be unpinned N times with + * drm_gem_vram_unpin(). The same applies to pairs of + * drm_gem_vram_kmap() and drm_gem_vram_kunmap(). */ struct drm_gem_vram_object { struct ttm_buffer_object bo; struct ttm_bo_kmap_obj kmap;
+ /** + * @kmap_use_count: + * + * Reference count on the virtual address. + * The address are un-mapped when the count reaches zero. + */ + unsigned int kmap_use_count; + /* Supported placements are %TTM_PL_VRAM and %TTM_PL_SYSTEM */ struct ttm_placement placement; struct ttm_place placements[2];