drm/panfrost: Provide a custom dma_buf implementation

Before we introduce cached CPU mappings, we want a dma_buf
implementation satisfying synchronization requests around CPU
accesses coming from a dma_buf exported by our driver. Let's
provide our own implementation relying on the default
gem_shmem_prime helpers designed for that purpose.

v5:
- New patch

v6:
- Collect R-b

v7:
- Hand-roll our own dma_buf boilerplate

v8:
- No changes

Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251208100841.730527-9-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 4f5f19eda587638bab52ec2f8b9e5171310d1d35..199073cc7d3f87741b6b603926fe68ea908aacf4 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -852,6 +852,7 @@ static const struct drm_driver panfrost_drm_driver = {
        .minor                  = 5,
 
        .gem_create_object      = panfrost_gem_create_object,
+       .gem_prime_import       = panfrost_gem_prime_import,
        .gem_prime_import_sg_table = panfrost_gem_prime_import_sg_table,
 #ifdef CONFIG_DEBUG_FS
        .debugfs_init = panfrost_debugfs_init,

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index c1688a542ec2647f233204910bc22c2a6c70a496..02721863b6ae624082858bfd78bab1b972fbee76 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -277,6 +277,128 @@ static size_t panfrost_gem_rss(struct drm_gem_object *obj)
        return 0;
 }
 
+static struct sg_table *
+panfrost_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
+                              enum dma_data_direction dir)
+{
+       struct sg_table *sgt = drm_gem_map_dma_buf(attach, dir);
+
+       if (!IS_ERR(sgt))
+               attach->priv = sgt;
+
+       return sgt;
+}
+
+static void
+panfrost_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
+                                struct sg_table *sgt,
+                                enum dma_data_direction dir)
+{
+       attach->priv = NULL;
+       drm_gem_unmap_dma_buf(attach, sgt, dir);
+}
+
+static int
+panfrost_gem_prime_begin_cpu_access(struct dma_buf *dma_buf,
+                                   enum dma_data_direction dir)
+{
+       struct drm_gem_object *obj = dma_buf->priv;
+       struct drm_device *dev = obj->dev;
+       struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+       struct dma_buf_attachment *attach;
+
+       dma_resv_lock(obj->resv, NULL);
+       if (shmem->sgt)
+               dma_sync_sgtable_for_cpu(dev->dev, shmem->sgt, dir);
+
+       if (shmem->vaddr)
+               invalidate_kernel_vmap_range(shmem->vaddr, shmem->base.size);
+
+       list_for_each_entry(attach, &dma_buf->attachments, node) {
+               struct sg_table *sgt = attach->priv;
+
+               if (sgt)
+                       dma_sync_sgtable_for_cpu(attach->dev, sgt, dir);
+       }
+       dma_resv_unlock(obj->resv);
+
+       return 0;
+}
+
+static int
+panfrost_gem_prime_end_cpu_access(struct dma_buf *dma_buf,
+                                 enum dma_data_direction dir)
+{
+       struct drm_gem_object *obj = dma_buf->priv;
+       struct drm_device *dev = obj->dev;
+       struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+       struct dma_buf_attachment *attach;
+
+       dma_resv_lock(obj->resv, NULL);
+       list_for_each_entry(attach, &dma_buf->attachments, node) {
+               struct sg_table *sgt = attach->priv;
+
+               if (sgt)
+                       dma_sync_sgtable_for_device(attach->dev, sgt, dir);
+       }
+
+       if (shmem->vaddr)
+               flush_kernel_vmap_range(shmem->vaddr, shmem->base.size);
+
+       if (shmem->sgt)
+               dma_sync_sgtable_for_device(dev->dev, shmem->sgt, dir);
+
+       dma_resv_unlock(obj->resv);
+       return 0;
+}
+
+static const struct dma_buf_ops panfrost_dma_buf_ops = {
+       .attach = drm_gem_map_attach,
+       .detach = drm_gem_map_detach,
+       .map_dma_buf = panfrost_gem_prime_map_dma_buf,
+       .unmap_dma_buf = panfrost_gem_prime_unmap_dma_buf,
+       .release = drm_gem_dmabuf_release,
+       .mmap = drm_gem_dmabuf_mmap,
+       .vmap = drm_gem_dmabuf_vmap,
+       .vunmap = drm_gem_dmabuf_vunmap,
+       .begin_cpu_access = panfrost_gem_prime_begin_cpu_access,
+       .end_cpu_access = panfrost_gem_prime_end_cpu_access,
+};
+
+static struct dma_buf *
+panfrost_gem_prime_export(struct drm_gem_object *obj, int flags)
+{
+       struct drm_device *dev = obj->dev;
+       struct dma_buf_export_info exp_info = {
+               .exp_name = KBUILD_MODNAME,
+               .owner = THIS_MODULE,
+               .ops = &panfrost_dma_buf_ops,
+               .size = obj->size,
+               .flags = flags,
+               .priv = obj,
+               .resv = obj->resv,
+       };
+
+       return drm_gem_dmabuf_export(dev, &exp_info);
+}
+
+struct drm_gem_object *
+panfrost_gem_prime_import(struct drm_device *dev,
+                         struct dma_buf *dma_buf)
+{
+       struct drm_gem_object *obj = dma_buf->priv;
+
+       if (dma_buf->ops == &panfrost_dma_buf_ops && obj->dev == dev) {
+               /* Importing dmabuf exported from our own gem increases
+                * refcount on gem itself instead of f_count of dmabuf.
+                */
+               drm_gem_object_get(obj);
+               return obj;
+       }
+
+       return drm_gem_prime_import(dev, dma_buf);
+}
+
 static const struct drm_gem_object_funcs panfrost_gem_funcs = {
        .free = panfrost_gem_free_object,
        .open = panfrost_gem_open,
@@ -285,6 +407,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
        .pin = panfrost_gem_pin,
        .unpin = drm_gem_shmem_object_unpin,
        .get_sg_table = drm_gem_shmem_object_get_sg_table,
+       .export = panfrost_gem_prime_export,
        .vmap = drm_gem_shmem_object_vmap,
        .vunmap = drm_gem_shmem_object_vunmap,
        .mmap = drm_gem_shmem_object_mmap,

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index 1a62529ff06fb95d1e55a277d56bc882001b18a0..c2470e8255ab4adfc1c18b4b6421d0b07eec8a2c 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -132,6 +132,9 @@ struct drm_gem_object *
 panfrost_gem_prime_import_sg_table(struct drm_device *dev,
                                   struct dma_buf_attachment *attach,
                                   struct sg_table *sgt);
+struct drm_gem_object *
+panfrost_gem_prime_import(struct drm_device *dev,
+                         struct dma_buf *dma_buf);
 
 struct panfrost_gem_object *
 panfrost_gem_create(struct drm_device *dev, size_t size, u32 flags);