[PATCH 3/3] drm/exynos: clone new sgt instead of creating from pages

[Inki Dae]

2012/11/7 Prathyush K <prathyush.k at samsung.com>

> During map_dma_buf, a new sgt needs to be created before being mapped to
> another device's address space. Currently, this sgt is created from
> the pages of the gem buffer everytime by calling dma_get_sgtable. This
> will be time consuming if the map/unmap calls are done repeatedly for
> very large buffers.
>
> Instead, we can just clone the sgt which was already created during
> buffer allocation and create the new sgt. This is done by calling
> 'sg_clone_table'. This will be much faster than creating from pages.
>
> Signed-off-by: Prathyush K <prathyush.k at samsung.com>
> ---
>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c |   10 +++++++---
>  1 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> index d9307bd..56efdd5 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> @@ -40,10 +40,14 @@ static struct sg_table *exynos_get_sgt(struct
> drm_device *drm_dev,
>         if (!sgt)
>                 goto out;
>
> -       ret = dma_get_sgtable(drm_dev->dev, sgt, buf->kvaddr,
> -                               buf->dma_addr, buf->size);
> +       if (!buf->sgt) {
> +               DRM_ERROR("sgt is null.\n");
> +               goto err_free_sgt;
> +       }
> +
> +       ret = sg_clone_table(buf->sgt, sgt, GFP_KERNEL);
>

I think it's good idea but may need review enough. Let me sleep on it.

Thanks,
Inki Dae



>         if (ret < 0) {
> -               DRM_ERROR("failed to get sgtable.\n");
> +               DRM_ERROR("failed to clone sgtable.\n");
>                 goto err_free_sgt;
>         }
>
> --
> 1.7.0.4
>
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