i965/gen4: Work around missing sRGB RGB DXT1 support.

The hardware just doesn't support it.  I suspect this was a regression from
the move to fixed MESA_FORMATs for compressed textures and that previously we
were storing uncompressed for this or something.

Fixes GPU hangs in piglit "texwrap GL_EXT_texture_sRGB-s3tc bordercolor
swizzled" on my GM965.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i965/brw_state.h

@@ -197,7 +197,8 @@ uint32_t brw_format_for_mesa_format(gl_format mesa_format);
 
 GLuint translate_tex_target(GLenum target);
 
-GLuint translate_tex_format(gl_format mesa_format,
+GLuint translate_tex_format(struct intel_context *intel,
+                            gl_format mesa_format,
 			    GLenum internal_format,
 			    GLenum depth_mode,
 			    GLenum srgb_decode);

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

@@ -622,7 +622,8 @@ brw_render_target_supported(struct intel_context *intel,
 }
 
 GLuint
-translate_tex_format(gl_format mesa_format,
+translate_tex_format(struct intel_context *intel,
+                     gl_format mesa_format,
 		     GLenum internal_format,
 		     GLenum depth_mode,
 		     GLenum srgb_decode)
@@ -651,6 +652,17 @@ translate_tex_format(gl_format mesa_format,
        */
       return BRW_SURFACEFORMAT_R32G32B32A32_FLOAT;
 
+   case MESA_FORMAT_SRGB_DXT1:
+      if (intel->gen == 4 && !intel->is_g4x) {
+         /* Work around missing SRGB DXT1 support on original gen4 by just
+          * skipping SRGB decode.  It's not worth not supporting sRGB in
+          * general to prevent this.
+          */
+         WARN_ONCE(true, "Demoting sRGB DXT1 texture to non-sRGB\n");
+         mesa_format = MESA_FORMAT_RGB_DXT1;
+      }
+      return brw_format_for_mesa_format(mesa_format);
+
    default:
       assert(brw_format_for_mesa_format(mesa_format) != 0);
       return brw_format_for_mesa_format(mesa_format);
@@ -829,6 +841,7 @@ brw_update_texture_surface(struct gl_context *ctx,
                            uint32_t *binding_table,
                            unsigned surf_index)
 {
+   struct intel_context *intel = intel_context(ctx);
    struct brw_context *brw = brw_context(ctx);
    struct gl_texture_object *tObj = ctx->Texture.Unit[unit]._Current;
    struct intel_texture_object *intelObj = intel_texture_object(tObj);
@@ -852,7 +865,8 @@ brw_update_texture_surface(struct gl_context *ctx,
    surf[0] = (translate_tex_target(tObj->Target) << BRW_SURFACE_TYPE_SHIFT |
 	      BRW_SURFACE_MIPMAPLAYOUT_BELOW << BRW_SURFACE_MIPLAYOUT_SHIFT |
 	      BRW_SURFACE_CUBEFACE_ENABLES |
-	      (translate_tex_format(mt->format,
+	      (translate_tex_format(intel,
+                                    mt->format,
 				    firstImage->InternalFormat,
 				    tObj->DepthMode,
 				    sampler->sRGBDecode) <<

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

@@ -309,7 +309,8 @@ gen7_update_texture_surface(struct gl_context *ctx,
                                     8 * 4, 32, &binding_table[surf_index]);
    memset(surf, 0, 8 * 4);
 
-   uint32_t tex_format = translate_tex_format(mt->format,
+   uint32_t tex_format = translate_tex_format(intel,
+                                              mt->format,
                                               firstImage->InternalFormat,
                                               tObj->DepthMode,
                                               sampler->sRGBDecode);