i965: Totally switch around how we handle nonzero baselevel-first_level.

This has no effect currently, because intel_finalize_mipmap_tree() always
makes mt->first_level == tObj->BaseLevel.

The change I made before to handle it
(b1080cfbdb) got very close to working, but
after fixing some unrelated bugs in the series, it still left
tex-miplevel-selection producing errors when testing textureLod().  The
problem is that for explicit LODs, the sampler's LOD clamping is ignored,
and only the surface's MIP clamping is respected.  So we need to use
surface mip clamping, which applies on top of the sampler's mip clamping,
so the sampler change gets backed out.

Now actually tested with a non-regressing series producing a non-zero
computed baselevel.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

src/mesa/drivers/dri/i965/brw_wm_sampler_state.c

@@ -202,8 +202,6 @@ static void brw_update_sampler_state(struct brw_context *brw,
    struct gl_context *ctx = &brw->ctx;
    struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
    struct gl_texture_object *texObj = texUnit->_Current;
-   struct intel_texture_image *intel_image =
-      intel_texture_image(texObj->Image[0][texObj->BaseLevel]);
    struct gl_sampler_object *gl_sampler = _mesa_get_samplerobj(ctx, unit);
    bool using_nearest = false;
 
@@ -322,13 +320,10 @@ static void brw_update_sampler_state(struct brw_context *brw,
    sampler->ss0.lod_preclamp = 1; /* OpenGL mode */
    sampler->ss0.default_color_mode = 0; /* OpenGL/DX10 mode */
 
-   int baselevel = texObj->BaseLevel - intel_image->mt->first_level;
-   sampler->ss0.base_level = U_FIXED(baselevel, 1);
+   sampler->ss0.base_level = U_FIXED(0, 1);
 
-   sampler->ss1.max_lod = U_FIXED(CLAMP(baselevel +
-                                        gl_sampler->MaxLod, 0, 13), 6);
-   sampler->ss1.min_lod = U_FIXED(CLAMP(baselevel +
-                                        gl_sampler->MinLod, 0, 13), 6);
+   sampler->ss1.max_lod = U_FIXED(CLAMP(gl_sampler->MaxLod, 0, 13), 6);
+   sampler->ss1.min_lod = U_FIXED(CLAMP(gl_sampler->MinLod, 0, 13), 6);
 
    /* On Gen6+, the sampler can handle non-normalized texture
     * rectangle coordinates natively

src/mesa/drivers/dri/i965/brw_wm_surface_state.c

@@ -279,7 +279,7 @@ brw_update_texture_surface(struct gl_context *ctx,
 
    surf[1] = intelObj->mt->region->bo->offset + intelObj->mt->offset; /* reloc */
 
-   surf[2] = ((intelObj->_MaxLevel - mt->first_level) << BRW_SURFACE_LOD_SHIFT |
+   surf[2] = ((intelObj->_MaxLevel - tObj->BaseLevel) << BRW_SURFACE_LOD_SHIFT |
 	      (mt->logical_width0 - 1) << BRW_SURFACE_WIDTH_SHIFT |
 	      (mt->logical_height0 - 1) << BRW_SURFACE_HEIGHT_SHIFT);
 
@@ -288,7 +288,8 @@ brw_update_texture_surface(struct gl_context *ctx,
 	      (intelObj->mt->region->pitch - 1) <<
 	      BRW_SURFACE_PITCH_SHIFT);
 
-   surf[4] = brw_get_surface_num_multisamples(intelObj->mt->num_samples);
+   surf[4] = (brw_get_surface_num_multisamples(intelObj->mt->num_samples) |
+              SET_FIELD(tObj->BaseLevel - mt->first_level, BRW_SURFACE_MIN_LOD));
 
    surf[5] = mt->align_h == 4 ? BRW_SURFACE_VERTICAL_ALIGN_ENABLE : 0;
 

src/mesa/drivers/dri/i965/gen7_sampler_state.c

@@ -41,8 +41,6 @@ gen7_update_sampler_state(struct brw_context *brw, int unit, int ss_index,
    struct gl_context *ctx = &brw->ctx;
    struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
    struct gl_texture_object *texObj = texUnit->_Current;
-   struct intel_texture_image *intel_image =
-      intel_texture_image(texObj->Image[0][texObj->BaseLevel]);
    struct gl_sampler_object *gl_sampler = _mesa_get_samplerobj(ctx, unit);
    bool using_nearest = false;
 
@@ -153,13 +151,10 @@ gen7_update_sampler_state(struct brw_context *brw, int unit, int ss_index,
    sampler->ss0.lod_preclamp = 1; /* OpenGL mode */
    sampler->ss0.default_color_mode = 0; /* OpenGL/DX10 mode */
 
-   int baselevel = texObj->BaseLevel - intel_image->mt->first_level;
-   sampler->ss0.base_level = U_FIXED(baselevel, 1);
+   sampler->ss0.base_level = U_FIXED(0, 1);
 
-   sampler->ss1.max_lod = U_FIXED(CLAMP(baselevel +
-                                        gl_sampler->MaxLod, 0, 13), 8);
-   sampler->ss1.min_lod = U_FIXED(CLAMP(baselevel +
-                                        gl_sampler->MinLod, 0, 13), 8);
+   sampler->ss1.max_lod = U_FIXED(CLAMP(gl_sampler->MaxLod, 0, 13), 8);
+   sampler->ss1.min_lod = U_FIXED(CLAMP(gl_sampler->MinLod, 0, 13), 8);
 
    /* The sampler can handle non-normalized texture rectangle coordinates
     * natively

src/mesa/drivers/dri/i965/gen7_wm_surface_state.c

@@ -348,8 +348,10 @@ gen7_update_texture_surface(struct gl_context *ctx,
    surf[4] = gen7_surface_msaa_bits(mt->num_samples, mt->msaa_layout);
 
    surf[5] = (SET_FIELD(GEN7_MOCS_L3, GEN7_SURFACE_MOCS) |
+              SET_FIELD(tObj->BaseLevel - mt->first_level,
+                        GEN7_SURFACE_MIN_LOD) |
               /* mip count */
-              (intelObj->_MaxLevel - mt->first_level));
+              (intelObj->_MaxLevel - tObj->BaseLevel));
 
    if (brw->is_haswell) {
       /* Handling GL_ALPHA as a surface format override breaks 1.30+ style