drm/panfrost: Add madvise and shrinker support

Add support for madvise and a shrinker similar to other drivers. This
allows userspace to mark BOs which can be freed when there is memory
pressure.

Unlike other implementations, we don't depend on struct_mutex. The
driver maintains a list of BOs which can be freed when the shrinker
is called. Access to the list is serialized with the shrinker_lock.

Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190805143358.21245-2-robh@kernel.org

1 files changed, 107 insertions, 0 deletions

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
new file mode 100644
index 000000000000..d191632b6197
--- /dev/null
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -0,0 +1,107 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Arm Ltd.
+ *
+ * Based on msm_gem_freedreno.c:
+ * Copyright (C) 2016 Red Hat
+ * Author: Rob Clark <robdclark@gmail.com>
+ */
+
+#include <linux/list.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_gem_shmem_helper.h>
+
+#include "panfrost_device.h"
+#include "panfrost_gem.h"
+#include "panfrost_mmu.h"
+
+static unsigned long
+panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
+{
+	struct panfrost_device *pfdev =
+		container_of(shrinker, struct panfrost_device, shrinker);
+	struct drm_gem_shmem_object *shmem;
+	unsigned long count = 0;
+
+	if (!mutex_trylock(&pfdev->shrinker_lock))
+		return 0;
+
+	list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
+		if (drm_gem_shmem_is_purgeable(shmem))
+			count += shmem->base.size >> PAGE_SHIFT;
+	}
+
+	mutex_unlock(&pfdev->shrinker_lock);
+
+	return count;
+}
+
+static void panfrost_gem_purge(struct drm_gem_object *obj)
+{
+	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+	mutex_lock(&shmem->pages_lock);
+
+	panfrost_mmu_unmap(to_panfrost_bo(obj));
+	drm_gem_shmem_purge_locked(obj);
+
+	mutex_unlock(&shmem->pages_lock);
+}
+
+static unsigned long
+panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
+{
+	struct panfrost_device *pfdev =
+		container_of(shrinker, struct panfrost_device, shrinker);
+	struct drm_gem_shmem_object *shmem, *tmp;
+	unsigned long freed = 0;
+
+	if (!mutex_trylock(&pfdev->shrinker_lock))
+		return SHRINK_STOP;
+
+	list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
+		if (freed >= sc->nr_to_scan)
+			break;
+		if (drm_gem_shmem_is_purgeable(shmem)) {
+			panfrost_gem_purge(&shmem->base);
+			freed += shmem->base.size >> PAGE_SHIFT;
+			list_del_init(&shmem->madv_list);
+		}
+	}
+
+	mutex_unlock(&pfdev->shrinker_lock);
+
+	if (freed > 0)
+		pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
+
+	return freed;
+}
+
+/**
+ * panfrost_gem_shrinker_init - Initialize panfrost shrinker
+ * @dev: DRM device
+ *
+ * This function registers and sets up the panfrost shrinker.
+ */
+void panfrost_gem_shrinker_init(struct drm_device *dev)
+{
+	struct panfrost_device *pfdev = dev->dev_private;
+	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
+	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
+	pfdev->shrinker.seeks = DEFAULT_SEEKS;
+	WARN_ON(register_shrinker(&pfdev->shrinker));
+}
+
+/**
+ * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
+ * @dev: DRM device
+ *
+ * This function unregisters the panfrost shrinker.
+ */
+void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
+{
+	struct panfrost_device *pfdev = dev->dev_private;
+
+	if (pfdev->shrinker.nr_deferred) {
+		unregister_shrinker(&pfdev->shrinker);
+	}
+}