[PATCH v3 08/12] drm/ttm: Use drm_memcpy_from_wc_dbm for TTM bo moves

[Matthew Auld]

On Fri, 21 May 2021 at 16:33, Thomas Hellström
<thomas.hellstrom at linux.intel.com> wrote:
>
> Use fast wc memcpy for reading out of wc memory for TTM bo moves.
>
> Cc: Dave Airlie <airlied at gmail.com>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo_util.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index 912cbe8e60a2..4a7d3d672f9a 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -31,6 +31,7 @@
>
>  #include <drm/ttm/ttm_bo_driver.h>
>  #include <drm/ttm/ttm_placement.h>
> +#include <drm/drm_memcpy.h>
>  #include <drm/drm_vma_manager.h>
>  #include <linux/dma-buf-map.h>
>  #include <linux/io.h>
> @@ -91,6 +92,7 @@ void ttm_move_memcpy(struct ttm_buffer_object *bo,
>         const struct ttm_kmap_iter_ops *src_ops = src_iter->ops;
>         struct ttm_tt *ttm = bo->ttm;
>         struct dma_buf_map src_map, dst_map;
> +       bool wc_memcpy;
>         pgoff_t i;
>
>         /* Single TTM move. NOP */
> @@ -114,11 +116,16 @@ void ttm_move_memcpy(struct ttm_buffer_object *bo,
>                 return;
>         }
>
> +       wc_memcpy = ((!src_ops->maps_tt || ttm->caching != ttm_cached) &&

Why do we only consider the caching value for the maps_tt case? Or am
I misreading this?

> +                    drm_has_memcpy_from_wc());
> +
>         for (i = 0; i < dst_mem->num_pages; ++i) {
>                 dst_ops->map_local(dst_iter, &dst_map, i);
>                 src_ops->map_local(src_iter, &src_map, i);
>
> -               if (!src_map.is_iomem && !dst_map.is_iomem) {
> +               if (wc_memcpy) {
> +                       drm_memcpy_from_wc_dbm(&dst_map, &src_map, PAGE_SIZE);

Do we need to check the return value here? memcpy_from_wc expects
certain address alignment, or is that always guaranteed here? Maybe
throw a warning just for paranoia?

> +               } else if (!src_map.is_iomem && !dst_map.is_iomem) {
>                         memcpy(dst_map.vaddr, src_map.vaddr, PAGE_SIZE);
>                 } else if (!src_map.is_iomem) {
>                         dma_buf_map_memcpy_to(&dst_map, src_map.vaddr,
> --
> 2.31.1
>