[PATCH v2 1/9] drm/gem-vram: Support pinning buffers to current location

[Gerd Hoffmann]

On Tue, Jun 11, 2019 at 03:03:36PM +0200, Thomas Zimmermann wrote:
> Pinning a buffer prevents it from being moved to a different memory
> location. For some operations, such as buffer updates, it is not
> important where the buffer is located. Setting the pin function's
> pl_flag argument to 0 will pin the buffer to whereever it is stored.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---
>  drivers/gpu/drm/drm_gem_vram_helper.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
> index 42ad80888df7..214f54b8920b 100644
> --- a/drivers/gpu/drm/drm_gem_vram_helper.c
> +++ b/drivers/gpu/drm/drm_gem_vram_helper.c
> @@ -224,7 +224,9 @@ EXPORT_SYMBOL(drm_gem_vram_offset);
>   *
>   * Pinning a buffer object ensures that it is not evicted from
>   * a memory region. A pinned buffer object has to be unpinned before
> - * it can be pinned to another region.
> + * it can be pinned to another region. If the pl_flag argument is 0,
> + * the buffer is pinned at its current location (video RAM or system
> + * memory).
>   *
>   * Returns:
>   * 0 on success, or
> @@ -242,7 +244,9 @@ int drm_gem_vram_pin(struct drm_gem_vram_object *gbo, unsigned long pl_flag)
>  	if (gbo->pin_count)
>  		goto out;
>  
> -	drm_gem_vram_placement(gbo, pl_flag);
> +	if (pl_flag)
> +		drm_gem_vram_placement(gbo, pl_flag);
> +
>  	for (i = 0; i < gbo->placement.num_placement; ++i)
>  		gbo->placements[i].flags |= TTM_PL_FLAG_NO_EVICT;
>  
> @@ -691,7 +695,7 @@ int drm_gem_vram_driver_gem_prime_pin(struct drm_gem_object *gem)
>  {
>  	struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(gem);
>  
> -	return drm_gem_vram_pin(gbo, DRM_GEM_VRAM_PL_FLAG_VRAM);
> +	return drm_gem_vram_pin(gbo, 0);

Not sure this is a good idea here.  If the bo happens to be in sysram
it can't be displayed any more.

> -	ret = drm_gem_vram_pin(gbo, DRM_GEM_VRAM_PL_FLAG_VRAM);
> +	ret = drm_gem_vram_pin(gbo, 0);

Likewise.

cheers,
  Gerd