[PATCH 4/4] etnaviv: hook up linear texture sampling support

[Lucas Stach]

Am Montag, den 21.01.2019, 07:50 +0100 schrieb Christian Gmeiner:
> If the GPU supports linear sampling, linear addressing mode
> will be used as default.
> 
> > Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
> ---
>  src/gallium/drivers/etnaviv/etnaviv_resource.c | 10 +++++++---
>  src/gallium/drivers/etnaviv/etnaviv_texture.c  |  4 +++-
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/src/gallium/drivers/etnaviv/etnaviv_resource.c b/src/gallium/drivers/etnaviv/etnaviv_resource.c
> index 9a7ebf3064e..7d24b1f03bd 100644
> --- a/src/gallium/drivers/etnaviv/etnaviv_resource.c
> +++ b/src/gallium/drivers/etnaviv/etnaviv_resource.c
> @@ -318,9 +318,9 @@ etna_resource_create(struct pipe_screen *pscreen,
>  {
>     struct etna_screen *screen = etna_screen(pscreen);
>  
> -   /* Figure out what tiling and address mode to use -- for now, assume that
> -    * texture cannot be linear. there is a capability LINEAR_TEXTURE_SUPPORT
> -    * (supported on gc880 and gc2000 at least), but not sure how it works.
> +   /* Figure out what tiling and address mode to use.
> +    * Textures are TILED or LINEAR. If LINEAR_TEXTURE_SUPPORT capability is
> +    * available LINEAR gets prefered.
>      * Buffers always have LINEAR layout.
>      */
>     unsigned layout = ETNA_LAYOUT_LINEAR;
> @@ -334,6 +334,10 @@ etna_resource_create(struct pipe_screen *pscreen,
>  
>        if (util_format_is_compressed(templat->format))
>           layout = ETNA_LAYOUT_LINEAR;
> +      else if (VIV_FEATURE(screen, chipMinorFeatures1, LINEAR_TEXTURE_SUPPORT)) {
> +         layout = ETNA_LAYOUT_LINEAR;
> +         mode = ETNA_ADDRESSING_MODE_LINEAR;
> +      }

Did you do any performance measurements with this change? I don't think
we generally want to prefer linear textures, as in theory they have
much worse texture cache hit rates. Also a lot of the async transfer
stuff currently depends on hitting the RS linear->tiled blit path for
optimal performance on uploads.

There are 2 cases where I think linear textures are useful:

1. Imported external buffers, where we might need to update the
internal tiled copy on each resource update. Getting rid of this blit
should help performance a good bit.

2. 8bpp formats that can't be tiled with the RS and would hit the
software fallback path. The tradeoff software tiling path vs. reduced
texture cache hit rates might still prefer linear textures.

Regards,
Lucas
 

>     } else if (templat->target != PIPE_BUFFER) {
>        bool want_multitiled = false;
>        bool want_supertiled = screen->specs.can_supertile;
> diff --git a/src/gallium/drivers/etnaviv/etnaviv_texture.c b/src/gallium/drivers/etnaviv/etnaviv_texture.c
> index 3993e31cec1..b06f20531fd 100644
> --- a/src/gallium/drivers/etnaviv/etnaviv_texture.c
> +++ b/src/gallium/drivers/etnaviv/etnaviv_texture.c
> @@ -172,7 +172,9 @@ etna_resource_sampler_compatible(struct etna_resource *res)
>     if (res->layout == ETNA_LAYOUT_SUPER_TILED && VIV_FEATURE(screen, chipMinorFeatures2, SUPERTILED_TEXTURE))
>        return true;
>  
> -   /* TODO: LINEAR_TEXTURE_SUPPORT */
> +   /* This GPU supports texturing from linear textures? */
> +   if (res->layout == ETNA_LAYOUT_LINEAR && VIV_FEATURE(screen, chipMinorFeatures1, LINEAR_TEXTURE_SUPPORT))
> +      return true;
>  
>     /* Otherwise, only support tiled layouts */
>     if (res->layout != ETNA_LAYOUT_TILED)