[Mesa-dev] [PATCH 6/8] i965/dri: Handle Y-tiled modifier

[Jason Ekstrand]

On Tue, Mar 21, 2017 at 1:45 PM, Ben Widawsky <ben at bwidawsk.net> wrote:

> This patch begins introducing how we'll actually handle the potentially
> many modifiers coming in from the API, how we'll store them, and the
> structure in the code to support it.
>
> Prior to this patch, the Y-tiled modifier would be entirely ignored. It
> shouldn't actually be used until this point because we've not bumped the
> DRIimage extension version (which is a requirement to use modifiers).
>
> Measuring later in the series with kmscube:
> Linear:
> Read bandwidth: 1048.44 MiB/s
> Write bandwidth: 1483.17 MiB/s
>
> Y-tiled:
> Read bandwidth: 471.13 MiB/s
> Write bandwidth: 589.10 MiB/s
>
> Similar functionality was introduced and then reverted here:
>
> commit 6a0d036483caf87d43ebe2edd1905873446c9589
> Author: Ben Widawsky <ben at bwidawsk.net>
> Date:   Thu Apr 21 20:14:58 2016 -0700
>
>     i965: Always use Y-tiled buffers on SKL+
>
> v2: Use last set bit instead of first set bit in modifiers to address
> bug found by Daniel Stone.
>
> v3: Use the new priority modifier selection thing. This nullifies the
> bug fixed by v2 also.
>
> Signed-off-by: Ben Widawsky <benjamin.widawsky at intel.com>
> Reviewed-by: Eric Engestrom <eric.engestrom at imgtec.com>
> Acked-by: Daniel Stone <daniels at collabora.com>
> Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
> ---
>  src/mesa/drivers/dri/i965/intel_screen.c | 36
> ++++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/intel_screen.c
> b/src/mesa/drivers/dri/i965/intel_screen.c
> index 8ba90f0a0c..8bb3aca946 100644
> --- a/src/mesa/drivers/dri/i965/intel_screen.c
> +++ b/src/mesa/drivers/dri/i965/intel_screen.c
> @@ -23,6 +23,7 @@
>   * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
>   */
>
> +#include <drm_fourcc.h>
>  #include <errno.h>
>  #include <time.h>
>  #include <unistd.h>
> @@ -518,11 +519,13 @@ intel_destroy_image(__DRIimage *image)
>  enum modifier_priority {
>     MODIFIER_PRIORITY_INVALID = 0,
>     MODIFIER_PRIORITY_LINEAR,
> +   MODIFIER_PRIORITY_Y,
>  };
>
>  const uint64_t priority_to_modifier[] = {
>     [MODIFIER_PRIORITY_INVALID] = DRM_FORMAT_MOD_INVALID,
>     [MODIFIER_PRIORITY_LINEAR] = DRM_FORMAT_MOD_LINEAR,
> +   [MODIFIER_PRIORITY_Y] = I915_FORMAT_MOD_Y_TILED,
>  };
>
>  static uint64_t
> @@ -530,11 +533,13 @@ select_best_modifier(struct gen_device_info *devinfo,
>                       const uint64_t *modifiers,
>                       const unsigned count)
>  {
> -
>     enum modifier_priority prio = MODIFIER_PRIORITY_INVALID;
>
>     for (int i = 0; i < count; i++) {
>        switch (modifiers[i]) {
> +      case I915_FORMAT_MOD_Y_TILED:
> +         prio = MAX2(prio, MODIFIER_PRIORITY_Y);
> +         break;
>        case DRM_FORMAT_MOD_LINEAR:
>           prio = MAX2(prio, MODIFIER_PRIORITY_LINEAR);
>           break;
> @@ -575,6 +580,9 @@ intel_create_image_common(__DRIscreen *dri_screen,
>     case DRM_FORMAT_MOD_LINEAR:
>        tiling = I915_TILING_NONE;
>        break;
> +   case I915_FORMAT_MOD_Y_TILED:
> +      tiling = I915_TILING_Y;
> +      break;
>     case DRM_FORMAT_MOD_INVALID:
>        if (modifiers)
>           return NULL;
> @@ -628,8 +636,26 @@ intel_create_image_with_modifiers(__DRIscreen
> *dri_screen,
>                                    const unsigned count,
>                                    void *loaderPrivate)
>  {
> -   return intel_create_image_common(dri_screen, width, height, format,
> 0, NULL,
> -                                    0, loaderPrivate);
> +   uint64_t local_mods[count];
> +   int local_count = 0;
> +
> +   /* This compacts the actual modifiers to the ones we know how to
> handle */
> +   for (int i = 0; i < count; i++) {
> +      switch (modifiers[i]) {
> +      case I915_FORMAT_MOD_Y_TILED:
> +      case DRM_FORMAT_MOD_LINEAR:
> +         local_mods[local_count++] = modifiers[i];
> +         break;
> +      case DRM_FORMAT_MOD_INVALID:
> +         unreachable("Invalid modifiers specified\n");
>

I don't think you want unreachable here.  The higher layers only check
modifier zero.  They don't walk the entire list.


> +      default:
> +         /* Modifiers from other vendors would land here. */
> +         break;
> +      }
> +   }
>

Also, what's the benifit of the local modifiers thing?  The
select_best_modifier can handle an arbitrarily long list so I don't see
what this is gaining us.


> +
> +   return intel_create_image_common(dri_screen, width, height, format, 0,
> +                                    local_mods, local_count,
> loaderPrivate);
>  }
>
>  static GLboolean
> @@ -1999,7 +2025,9 @@ intelAllocateBuffer(__DRIscreen *dri_screen,
>     if (intelBuffer == NULL)
>        return NULL;
>
> -   /* The front and back buffers are color buffers, which are X tiled. */
> +   /* The front and back buffers are color buffers, which are X tiled.
> GEN9+
> +    * supports Y tiled and compressed buffers, but there is no way to
> plumb that
> +    * through to here. */
>     uint32_t tiling = I915_TILING_X;
>     unsigned long pitch;
>     int cpp = format / 8;
> --
> 2.12.0
>
>
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