[PATCH 1/6] drm/rockchip: import dma_buf to gem
From: Russell King - ARM Linux <hidden>
Date: 2015-06-18 10:59:20
Also in:
dri-devel, linux-rockchip, lkml
On Thu, Jun 18, 2015 at 03:49:25PM +0800, Mark Yao wrote:
quoted hunk ↗ jump to hunk
We want to display a buffer allocated by other driver, need import the buffer to gem. Signed-off-by: Mark Yao <redacted> --- 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.