On Mon, Nov 13, 2017 at 12:32:28PM +0200, Laurent Pinchart wrote:
> When the DU sources its frames from a VSP, it performs no memory access
> and thus has no requirements on imported dma-buf memory types. In
> particular the DU could import a physically non-contiguous buffer that
> would later be mapped contiguously through the VSP IOMMU.
>
> This use case isn't supported at the moment as the GEM CMA helpers will
> reject any non-contiguous buffer, and the DU isn't connected to an IOMMU
> that can make the buffer contiguous for DMA. Fix this by implementing a
> custom .gem_prime_import_sg_table() operation that accepts all imported
> dma-buf regardless of the number of scatterlist entries.
This patch raises the question of why use CMA at all if you can accept
any kind of buffers.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/rcar-du/rcar_du_drv.c | 2 +-
> drivers/gpu/drm/rcar-du/rcar_du_kms.c | 39 +++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/rcar-du/rcar_du_kms.h | 7 +++++++
> 3 files changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_drv.c b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> index 48c166f925a3..d999231f98c7 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> @@ -289,7 +289,7 @@ static struct drm_driver rcar_du_driver = {
> .gem_prime_import = drm_gem_prime_import,
> .gem_prime_export = drm_gem_prime_export,
> .gem_prime_get_sg_table = drm_gem_cma_prime_get_sg_table,
> - .gem_prime_import_sg_table = drm_gem_cma_prime_import_sg_table,
> + .gem_prime_import_sg_table = rcar_du_gem_prime_import_sg_table,
> .gem_prime_vmap = drm_gem_cma_prime_vmap,
> .gem_prime_vunmap = drm_gem_cma_prime_vunmap,
> .gem_prime_mmap = drm_gem_cma_prime_mmap,
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> index 566d1a948c8f..2dd0c2ba047d 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> @@ -20,6 +20,7 @@
> #include <drm/drm_gem_cma_helper.h>
> #include <drm/drm_gem_framebuffer_helper.h>
>
> +#include <linux/dma-buf.h>
> #include <linux/of_graph.h>
> #include <linux/wait.h>
>
> @@ -148,6 +149,44 @@ const struct rcar_du_format_info *rcar_du_format_info(u32 fourcc)
> * Frame buffer
> */
>
> +struct drm_gem_object *rcar_du_gem_prime_import_sg_table(struct drm_device *dev,
> + struct dma_buf_attachment *attach,
> + struct sg_table *sgt)
> +{
> + struct rcar_du_device *rcdu = dev->dev_private;
> + struct drm_gem_cma_object *cma_obj;
> + struct drm_gem_object *gem_obj;
> + int ret;
> +
> + if (!rcar_du_has(rcdu, RCAR_DU_FEATURE_VSP1_SOURCE))
> + return drm_gem_cma_prime_import_sg_table(dev, attach, sgt);
> +
> + /* Create a CMA GEM buffer. */
> + cma_obj = kzalloc(sizeof(*cma_obj), GFP_KERNEL);
> + if (!cma_obj)
> + return ERR_PTR(-ENOMEM);
> + gem_obj = &cma_obj->base;
> +
> + ret = drm_gem_object_init(dev, gem_obj, attach->dmabuf->size);
> + if (ret)
> + goto error;
> +
> + ret = drm_gem_create_mmap_offset(gem_obj);
> + if (ret) {
> + drm_gem_object_release(gem_obj);
> + goto error;
> + }
> +
> + cma_obj->paddr = 0;
This is going to break drm_gem_cma_describe() if you are using it plus
the rcar_du_plane_setup_scanout() unless I'm missing something besides
familiarity with the RCAR driver code :)
This function looks very similar to what I tried to do for mali-dp to
allow the import of contiguous DMA buffers that have more than 1 sgt
entries. In the end I gave up as I kept finding issues and went for the
drm_gem_cma_prime_import_sg_table() changes. Maybe you need to do a
similar change in the function to bypass some requirements if the driver
signals that it can accept relaxed requirements?
Best regards,
Liviu
> + cma_obj->sgt = sgt;
> +
> + return gem_obj;
> +
> +error:
> + kfree(cma_obj);
> + return ERR_PTR(ret);
> +}
> +
> int rcar_du_dumb_create(struct drm_file *file, struct drm_device *dev,
> struct drm_mode_create_dumb *args)
> {
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.h b/drivers/gpu/drm/rcar-du/rcar_du_kms.h
> index 07951d5fe38b..10b2bb0f0df9 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.h
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.h
> @@ -16,10 +16,13 @@
>
> #include <linux/types.h>
>
> +struct dma_buf_attachment;
> struct drm_file;
> struct drm_device;
> +struct drm_gem_object;
> struct drm_mode_create_dumb;
> struct rcar_du_device;
> +struct sg_table;
>
> struct rcar_du_format_info {
> u32 fourcc;
> @@ -36,4 +39,8 @@ int rcar_du_modeset_init(struct rcar_du_device *rcdu);
> int rcar_du_dumb_create(struct drm_file *file, struct drm_device *dev,
> struct drm_mode_create_dumb *args);
>
> +struct drm_gem_object *rcar_du_gem_prime_import_sg_table(struct drm_device *dev,
> + struct dma_buf_attachment *attach,
> + struct sg_table *sgt);
> +
> #endif /* __RCAR_DU_KMS_H__ */
> --
> Regards,
>
> Laurent Pinchart
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯
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