[Mesa-dev] [PATCH 3/3] i965/sampler_state: Set the "Base Mip Level" field on Sandy Bridge

[Jason Ekstrand]

Fixes two GL ES 3.0 CTS tests on Sandy Bridge:

ES3-CTS.functional.texture.mipmap.cube.base_level.linear_linear
ES3-CTS.functional.texture.mipmap.cube.base_level.linear_nearest

Cc: "17.0 13.0" <mesa-stable at lists.freedesktop.org>
---
 src/mesa/drivers/dri/i965/brw_sampler_state.c | 20 +++++++++++++++++++-
 src/mesa/drivers/dri/i965/brw_state.h         |  1 +
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_sampler_state.c b/src/mesa/drivers/dri/i965/brw_sampler_state.c
index 1cf10a8..b99a898 100644
--- a/src/mesa/drivers/dri/i965/brw_sampler_state.c
+++ b/src/mesa/drivers/dri/i965/brw_sampler_state.c
@@ -88,6 +88,7 @@ brw_emit_sampler_state(struct brw_context *brw,
                        unsigned wrap_s,
                        unsigned wrap_t,
                        unsigned wrap_r,
+                       unsigned base_level,
                        unsigned min_lod,
                        unsigned max_lod,
                        int lod_bias,
@@ -132,6 +133,21 @@ brw_emit_sampler_state(struct brw_context *brw,
       ss[0] |= SET_FIELD(lod_bias & 0x7ff, GEN4_SAMPLER_LOD_BIAS) |
                SET_FIELD(shadow_function, GEN4_SAMPLER_SHADOW_FUNCTION);
 
+      /* This field has existed since the original i965, but is declared MBZ
+       * until Sandy Bridge.  According to the PRM:
+       *
+       *    "This was added to match OpenGL semantics"
+       *
+       * In particular, OpenGL allowed you to offset by 0.5 in certain cases
+       * to get slightly better filtering.  On Ivy Bridge and above, it
+       * appears that this is added to RENDER_SURFACE_STATE::SurfaceMinLOD so
+       * the right value is 0.0 or 0.5 (if you want the wacky behavior).  On
+       * Sandy Bridge, however, this sum does not seem to occur and you have
+       * to set it to the actual base level of the texture.
+       */
+      if (brw->gen == 6)
+         ss[0] |= SET_FIELD(base_level, BRW_SAMPLER_BASE_MIPLEVEL);
+
       if (brw->gen == 6 && min_filter != mag_filter)
          ss[0] |= GEN6_SAMPLER_MIN_MAG_NOT_EQUAL;
 
@@ -503,6 +519,8 @@ brw_update_sampler_state(struct brw_context *brw,
 
    const int lod_bits = brw->gen >= 7 ? 8 : 6;
    const float hw_max_lod = brw->gen >= 7 ? 14 : 13;
+   const unsigned base_level =
+      U_FIXED(CLAMP(texObj->MinLevel + texObj->BaseLevel, 0, hw_max_lod), 1);
    const unsigned min_lod =
       U_FIXED(CLAMP(sampler->MinLod, 0, hw_max_lod), lod_bits);
    const unsigned max_lod =
@@ -532,7 +550,7 @@ brw_update_sampler_state(struct brw_context *brw,
                           max_anisotropy,
                           address_rounding,
                           wrap_s, wrap_t, wrap_r,
-                          min_lod, max_lod, lod_bias,
+                          base_level, min_lod, max_lod, lod_bias,
                           shadow_function,
                           non_normalized_coords,
                           border_color_offset);
diff --git a/src/mesa/drivers/dri/i965/brw_state.h b/src/mesa/drivers/dri/i965/brw_state.h
index 36307c7..4b7e3c2 100644
--- a/src/mesa/drivers/dri/i965/brw_state.h
+++ b/src/mesa/drivers/dri/i965/brw_state.h
@@ -335,6 +335,7 @@ void brw_emit_sampler_state(struct brw_context *brw,
                             unsigned wrap_s,
                             unsigned wrap_t,
                             unsigned wrap_r,
+                            unsigned base_level,
                             unsigned min_lod,
                             unsigned max_lod,
                             int lod_bias,
-- 
2.5.0.400.gff86faf