On Thu, Jun 18, 2015 at 03:49:25PM +0800, Mark Yao wrote:
> We want to display a buffer allocated by other driver, need import
> the buffer to gem.
>
> Signed-off-by: Mark Yao <mark.yao@xxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 1 +
> drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 45 +++++++++++++++++++++++++--
> drivers/gpu/drm/rockchip/rockchip_drm_gem.h | 5 ++-
> 3 files changed, 47 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> index 3962176..9001a90 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> @@ -287,6 +287,7 @@ static struct drm_driver rockchip_drm_driver = {
> .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
> .gem_prime_import = drm_gem_prime_import,
> + .gem_prime_import_sg_table = rockchip_gem_prime_import_sg_table,
> .gem_prime_export = drm_gem_prime_export,
> .gem_prime_get_sg_table = rockchip_gem_prime_get_sg_table,
> .gem_prime_vmap = rockchip_gem_prime_vmap,
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> index eb2282c..2e30e23 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> @@ -18,6 +18,7 @@
> #include <drm/drm_vma_manager.h>
>
> #include <linux/dma-attrs.h>
> +#include <linux/dma-buf.h>
>
> #include "rockchip_drm_drv.h"
> #include "rockchip_drm_gem.h"
> @@ -105,6 +106,38 @@ int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
> return ret;
> }
>
> +struct drm_gem_object *
> +rockchip_gem_prime_import_sg_table(struct drm_device *drm,
> + struct dma_buf_attachment *attach,
> + struct sg_table *sgt)
> +{
> + struct rockchip_gem_object *rk_obj;
> + struct drm_gem_object *obj;
> + int ret;
> +
> + rk_obj = kzalloc(sizeof(*rk_obj), GFP_KERNEL);
> + if (!rk_obj)
> + return ERR_PTR(-ENOMEM);
> +
> + obj = &rk_obj->base;
> +
> + drm_gem_private_object_init(drm, obj, attach->dmabuf->size);
> +
> + if (!dma_map_sg(drm->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE)) {
> + ret = -ENOMEM;
> + goto err_free_obj;
> + }
> + rk_obj->dma_addr = sg_dma_address(sgt->sgl);
> + rk_obj->sgt = sgt;
> + obj->size = sg_dma_len(sgt->sgl);
This is wrong.
First, if you can only cope with a single scatterlist entry, you need to
enforce that. You can do that in your gem_prime_import_sg_table() method
by checking sgt->nents.
Secondly, you're mapping an already mapped scatterlist - scatterlists
are mapped by the exporter inside dma_buf_map_attachment() for your
device.
Thirdly, I hate drm_gem_prime_import() being used on ARM... it forces
drivers to do something very buggy: the DMA buffer is mapped for DMA
when the buffer is imported. If the buffer is a write-combine or cached
buffer, writes to the buffer after the import will not become visible to
the display hardware until sometime later (when they're evicted from the
caches and/or pushed out of the bus structure.) The DMA mapping should
be performed as close to the start of DMA as possible. However, this is
a long-standing issue I have with dma_buf itself and is not something you
should be too concerned with in your patch. Just bear it in mind if you
start to see corruption of imported buffers - the answer is not more
dma_map_sg() calls, but to get dma_buf fixed.
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
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