drm: Replace drm_gem_vram_push_to_system() with kunmap + unpin

The push-to-system function forces a buffer out of video RAM. This decision
should rather be made by the memory manager. By replacing the function with
calls to the kunmap and unpin functions, the buffer's memory becomes available,
but the buffer remains in VRAM until it's evicted by a pin operation.

This patch replaces the remaining instances of drm_gem_vram_push_to_system()
in ast and mgag200, and removes the function from DRM.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20190521110831.20200-2-tzimmermann@suse.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/ast/ast_mode.c

@@ -521,7 +521,6 @@ static void ast_crtc_dpms(struct drm_crtc *crtc, int mode)
 	}
 }
 
-/* ast is different - we will force move buffers out of VRAM */
 static int ast_crtc_do_set_base(struct drm_crtc *crtc,
 				struct drm_framebuffer *fb,
 				int x, int y, int atomic)
@@ -534,12 +533,15 @@ static int ast_crtc_do_set_base(struct drm_crtc *crtc,
 	s64 gpu_addr;
 	void *base;
 
-	/* push the previous fb to system ram */
 	if (!atomic && fb) {
 		ast_fb = to_ast_framebuffer(fb);
 		obj = ast_fb->obj;
 		gbo = drm_gem_vram_of_gem(obj);
-		drm_gem_vram_push_to_system(gbo);
+
+		/* unmap if console */
+		if (&ast->fbdev->afb == ast_fb)
+			drm_gem_vram_kunmap(gbo);
+		drm_gem_vram_unpin(gbo);
 	}
 
 	ast_fb = to_ast_framebuffer(crtc->primary->fb);
@@ -622,11 +624,15 @@ static void ast_crtc_disable(struct drm_crtc *crtc)
 	DRM_DEBUG_KMS("\n");
 	ast_crtc_dpms(crtc, DRM_MODE_DPMS_OFF);
 	if (crtc->primary->fb) {
+		struct ast_private *ast = crtc->dev->dev_private;
 		struct ast_framebuffer *ast_fb = to_ast_framebuffer(crtc->primary->fb);
 		struct drm_gem_object *obj = ast_fb->obj;
 		struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(obj);
 
-		drm_gem_vram_push_to_system(gbo);
+		/* unmap if console */
+		if (&ast->fbdev->afb == ast_fb)
+			drm_gem_vram_kunmap(gbo);
+		drm_gem_vram_unpin(gbo);
 	}
 	crtc->primary->fb = NULL;
 }

drivers/gpu/drm/drm_gem_vram_helper.c

@@ -379,56 +379,6 @@ int drm_gem_vram_unpin_reserved(struct drm_gem_vram_object *gbo)
 }
 EXPORT_SYMBOL(drm_gem_vram_unpin_reserved);
 
-/**
- * drm_gem_vram_push_to_system() - \
-	Unpins a GEM VRAM object and moves it to system memory
- * @gbo:	the GEM VRAM object
- *
- * This operation only works if the caller holds the final pin on the
- * buffer object.
- *
- * Returns:
- * 0 on success, or
- * a negative error code otherwise.
- */
-int drm_gem_vram_push_to_system(struct drm_gem_vram_object *gbo)
-{
-	int i, ret;
-	struct ttm_operation_ctx ctx = { false, false };
-
-	ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
-	if (ret < 0)
-		return ret;
-
-	if (WARN_ON_ONCE(!gbo->pin_count))
-		goto out;
-
-	--gbo->pin_count;
-	if (gbo->pin_count)
-		goto out;
-
-	if (gbo->kmap.virtual)
-		ttm_bo_kunmap(&gbo->kmap);
-
-	drm_gem_vram_placement(gbo, TTM_PL_FLAG_SYSTEM);
-	for (i = 0; i < gbo->placement.num_placement ; ++i)
-		gbo->placements[i].flags |= TTM_PL_FLAG_NO_EVICT;
-
-	ret = ttm_bo_validate(&gbo->bo, &gbo->placement, &ctx);
-	if (ret)
-		goto err_ttm_bo_unreserve;
-
-out:
-	ttm_bo_unreserve(&gbo->bo);
-
-	return 0;
-
-err_ttm_bo_unreserve:
-	ttm_bo_unreserve(&gbo->bo);
-	return ret;
-}
-EXPORT_SYMBOL(drm_gem_vram_push_to_system);
-
 /**
  * drm_gem_vram_kmap_at() - Maps a GEM VRAM object into kernel address space
  * @gbo:	the GEM VRAM object

drivers/gpu/drm/drm_vram_helper_common.c

@@ -79,8 +79,6 @@
  * RAM. Call drm_gem_vram_pin() with &DRM_GEM_VRAM_PL_FLAG_VRAM or
  * &DRM_GEM_VRAM_PL_FLAG_SYSTEM to pin a buffer object in video RAM or system
  * memory. Call drm_gem_vram_unpin() to release the pinned object afterwards.
- * If you have to evict a buffer object from video RAM (e.g., for freeing up
- * memory), unpin the buffer and call drm_gem_vram_push_to_system().
  *
  * A buffer object that is pinned in video RAM has a fixed address within that
  * memory region. Call drm_gem_vram_offset() to retrieve this value. Typically

drivers/gpu/drm/mgag200/mgag200_mode.c

@@ -858,8 +858,6 @@ static void mga_set_start_address(struct drm_crtc *crtc, unsigned offset)
 	WREG_ECRT(0x0, ((u8)(addr >> 16) & 0xf) | crtcext0);
 }
 
-
-/* ast is different - we will force move buffers out of VRAM */
 static int mga_crtc_do_set_base(struct drm_crtc *crtc,
 				struct drm_framebuffer *fb,
 				int x, int y, int atomic)
@@ -872,12 +870,15 @@ static int mga_crtc_do_set_base(struct drm_crtc *crtc,
 	s64 gpu_addr;
 	void *base;
 
-	/* push the previous fb to system ram */
 	if (!atomic && fb) {
 		mga_fb = to_mga_framebuffer(fb);
 		obj = mga_fb->obj;
 		gbo = drm_gem_vram_of_gem(obj);
-		drm_gem_vram_push_to_system(gbo);
+
+		/* unmap if console */
+		if (&mdev->mfbdev->mfb == mga_fb)
+			drm_gem_vram_kunmap(gbo);
+		drm_gem_vram_unpin(gbo);
 	}
 
 	mga_fb = to_mga_framebuffer(crtc->primary->fb);
@@ -1425,11 +1426,15 @@ static void mga_crtc_disable(struct drm_crtc *crtc)
 	DRM_DEBUG_KMS("\n");
 	mga_crtc_dpms(crtc, DRM_MODE_DPMS_OFF);
 	if (crtc->primary->fb) {
+		struct mga_device *mdev = crtc->dev->dev_private;
 		struct mga_framebuffer *mga_fb = to_mga_framebuffer(crtc->primary->fb);
 		struct drm_gem_object *obj = mga_fb->obj;
 		struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(obj);
 
-		drm_gem_vram_push_to_system(gbo);
+		/* unmap if console */
+		if (&mdev->mfbdev->mfb == mga_fb)
+			drm_gem_vram_kunmap(gbo);
+		drm_gem_vram_unpin(gbo);
 	}
 	crtc->primary->fb = NULL;
 }

include/drm/drm_gem_vram_helper.h

@@ -86,7 +86,6 @@ int drm_gem_vram_pin_reserved(struct drm_gem_vram_object *gbo,
 			      unsigned long pl_flag);
 int drm_gem_vram_unpin(struct drm_gem_vram_object *gbo);
 int drm_gem_vram_unpin_reserved(struct drm_gem_vram_object *gbo);
-int drm_gem_vram_push_to_system(struct drm_gem_vram_object *gbo);
 void *drm_gem_vram_kmap_at(struct drm_gem_vram_object *gbo, bool map,
 			   bool *is_iomem, struct ttm_bo_kmap_obj *kmap);
 void *drm_gem_vram_kmap(struct drm_gem_vram_object *gbo, bool map,