drm/vc4: Add the DRM_IOCTL_VC4_GEM_MADVISE ioctl

This ioctl will allow us to purge inactive userspace buffers when the
system is running out of contiguous memory.

For now, the purge logic is rather dumb in that it does not try to
release only the amount of BO needed to meet the last CMA alloc request
but instead purges all objects placed in the purgeable pool as soon as
we experience a CMA allocation failure.

Note that the in-kernel BO cache is always purged before the purgeable
cache because those objects are known to be unused while objects marked
as purgeable by a userspace application/library might have to be
restored when they are marked back as unpurgeable, which can be
expensive.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019125748.3152-1-boris.brezillon@free-electrons.com

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 3a767a038f72..423a23ed8fc2 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -23,6 +23,7 @@
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_plane_helper.h>
 
+#include "uapi/drm/vc4_drm.h"
 #include "vc4_drv.h"
 #include "vc4_regs.h"
 
@@ -774,21 +775,40 @@ static int vc4_prepare_fb(struct drm_plane *plane,
 {
 	struct vc4_bo *bo;
 	struct dma_fence *fence;
+	int ret;
 
 	if ((plane->state->fb == state->fb) || !state->fb)
 		return 0;
 
 	bo = to_vc4_bo(&drm_fb_cma_get_gem_obj(state->fb, 0)->base);
+
+	ret = vc4_bo_inc_usecnt(bo);
+	if (ret)
+		return ret;
+
 	fence = reservation_object_get_excl_rcu(bo->resv);
 	drm_atomic_set_fence_for_plane(state, fence);
 
 	return 0;
 }
 
+static void vc4_cleanup_fb(struct drm_plane *plane,
+			   struct drm_plane_state *state)
+{
+	struct vc4_bo *bo;
+
+	if (plane->state->fb == state->fb || !state->fb)
+		return;
+
+	bo = to_vc4_bo(&drm_fb_cma_get_gem_obj(state->fb, 0)->base);
+	vc4_bo_dec_usecnt(bo);
+}
+
 static const struct drm_plane_helper_funcs vc4_plane_helper_funcs = {
 	.atomic_check = vc4_plane_atomic_check,
 	.atomic_update = vc4_plane_atomic_update,
 	.prepare_fb = vc4_prepare_fb,
+	.cleanup_fb = vc4_cleanup_fb,
 };
 
 static void vc4_plane_destroy(struct drm_plane *plane)