[Mesa-dev] [PATCH 1/2] st/va: ensure linear memory for dmabuf

[Emil Velikov]

On 27 November 2015 at 08:57, Julien Isorce <j.isorce at samsung.com> wrote:
> In order to do zero-copy between two different devices
> the memory should not be tiled.
>
> This is currently no way to set pipe_resource template's flag
> from pipe_video_buffer template. So disabled_tiling is added.
>
> Choosed "disable" prefix so that CALLOC keeps tiling enabled
> by default.
>
> Tested with GStreamer on a laptop that has 2 GPUs:
> 1- gstvaapidecode:
>    HW decoding and dmabuf export with nouveau driver on Nvidia GPU.
> 2- glimagesink:
>    EGLImage imports dmabuf on Intel GPU.
>
> Note that tiling is working if 1 and 2 are done on the same GPU.
> So it is up to the application to set or not the flag:
> VA_SURFACE_EXTBUF_DESC_ENABLE_TILING
>
> Signed-off-by: Julien Isorce <j.isorce at samsung.com>
> ---
>  src/gallium/auxiliary/vl/vl_video_buffer.c | 3 +++
>  src/gallium/include/pipe/p_video_codec.h   | 1 +
>  src/gallium/state_trackers/va/surface.c    | 5 +++++
>  3 files changed, 9 insertions(+)
>
> diff --git a/src/gallium/auxiliary/vl/vl_video_buffer.c b/src/gallium/auxiliary/vl/vl_video_buffer.c
> index 6cd2557..62f4aa9 100644
> --- a/src/gallium/auxiliary/vl/vl_video_buffer.c
> +++ b/src/gallium/auxiliary/vl/vl_video_buffer.c
> @@ -253,6 +253,9 @@ vl_video_buffer_template(struct pipe_resource *templ,
>     templ->bind = PIPE_BIND_SAMPLER_VIEW | PIPE_BIND_RENDER_TARGET;
>     templ->usage = usage;
>
> +   if (tmpl->disable_tiling)
> +      templ->bind |= PIPE_BIND_LINEAR;
> +
>     if (plane > 0) {
>        if (tmpl->chroma_format == PIPE_VIDEO_CHROMA_FORMAT_420) {
>           templ->width0 /= 2;
> diff --git a/src/gallium/include/pipe/p_video_codec.h b/src/gallium/include/pipe/p_video_codec.h
> index 196d00b..dbfffd9 100644
> --- a/src/gallium/include/pipe/p_video_codec.h
> +++ b/src/gallium/include/pipe/p_video_codec.h
> @@ -125,6 +125,7 @@ struct pipe_video_buffer
>     enum pipe_video_chroma_format chroma_format;
>     unsigned width;
>     unsigned height;
> +   bool disable_tiling;
>     bool interlaced;
>
>     /**
> diff --git a/src/gallium/state_trackers/va/surface.c b/src/gallium/state_trackers/va/surface.c
> index c052c8f..f7043ad 100644
> --- a/src/gallium/state_trackers/va/surface.c
> +++ b/src/gallium/state_trackers/va/surface.c
> @@ -616,6 +616,11 @@ vlVaCreateSurfaces2(VADriverContextP ctx, unsigned int format,
>
>        switch (memory_type) {
>        case VA_SURFACE_ATTRIB_MEM_TYPE_VA:
> +         /* The application will clear the TILING flag when the surface is
> +          * intended to be exported as dmabuf. */
> +         templat.disable_tiling = memory_attibute &&
> +            !(memory_attibute->flags & VA_SURFACE_EXTBUF_DESC_ENABLE_TILING);
The condition seems to be flipped, no ? Currently it's doing
"disable_tiling = ENABLE_TILING_BIT_SET"

Other than that, the idea is ok imho, although I'd appreciate
Christian and others' feedback.

A few things worth mentioning while looking around for this:
 - suface_from_external_memory should (must) also know about disable_tiling.
 - missing R in function name ^^ suRface_ ...
 - sometimes radeon (see r600_video_buffer_create) completely
overwrites the existing flags, as opposed to just set the linear bit.
Bug, intentional, worth adding a comment ?
 - in many cases nouveau won't create a linear surface as it's not
using the above vl helper (hint, earlier suggesting about
reworking/cleaning things up a bit, hint)

Thanks
Emil