[Mesa-dev] [PATCH 12/34] i965: Handle Y-tile modifier

[Ben Widawsky]

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).

With X-tiling:
Writes:          6,583.58 MiB
Reads:           6,540.93 MiB

With Y-tiling:
Writes:          5,361.78 MiB
Reads            6,052.45 MiB

Savings per frame
Writes:  2 MiB
Reads:  .8 MiB

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+

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>
---
 src/mesa/drivers/dri/i965/intel_screen.c | 55 ++++++++++++++++++++++++++++----
 1 file changed, 49 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index ebfa74a8ff..6eaf146181 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>
@@ -559,16 +560,35 @@ select_best_modifier(struct gen_device_info *devinfo,
                      const uint64_t *modifiers,
                      const unsigned count)
 {
-   uint64_t modifier = DRM_FORMAT_MOD_INVALID;
+#define YTILE  (1 << 1)
+#define LINEAR (1 << 0)
+
+   const uint64_t prio_modifiers[] = { I915_FORMAT_MOD_Y_TILED, DRM_FORMAT_MOD_LINEAR };
+   uint32_t modifier_bitmask = 0; /* API only allows 32 */
 
    for (int i = 0; i < count; i++) {
       switch (modifiers[i]) {
       case DRM_FORMAT_MOD_LINEAR:
-         return modifiers[i];
+         modifier_bitmask |= LINEAR;
+         break;
+      case I915_FORMAT_MOD_Y_TILED:
+         if (devinfo->gen < 9) {
+            _mesa_warning(NULL, "Invalid Y-tiling parameter\n");
+            continue;
+         }
+
+         modifier_bitmask |= YTILE;
+         break;
       }
    }
 
-   return modifier;
+   if (modifier_bitmask)
+      return prio_modifiers[ffsll(modifier_bitmask)-1];
+
+   return DRM_FORMAT_MOD_INVALID;
+
+#undef LINEAR
+#undef YTILE
 }
 
 static __DRIimage *
@@ -599,6 +619,9 @@ __intel_create_image(__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:
    default:
          break;
@@ -650,8 +673,26 @@ intel_create_image_with_modifiers(__DRIscreen *dri_screen,
                                   const unsigned count,
                                   void *loaderPrivate)
 {
-   return __intel_create_image(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");
+      default:
+         /* Modifiers from other vendors would land here. */
+         break;
+      }
+   }
+
+   return __intel_create_image(dri_screen, width, height, format, 0,
+                               local_mods, local_count, loaderPrivate);
 }
 
 static GLboolean
@@ -1912,7 +1953,9 @@ 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;
-- 
2.11.0