crocus: don't map scanout buffers as write-back

This essentially ports 6440523077
Author: Keith Packard <keithp@keithp.com>
Date:   Fri Aug 6 16:11:18 2021 -0700

    iris: Map scanout buffers WC instead of WB [v2]

to crocus.

Fixes: f3630548f1 ("crocus: initial gallium driver for Intel gfx 4-7")

Reviewed-by: Zoltán Böszörményi <zboszor@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15313>
(cherry picked from commit e8c3be0eb8)

.pick_status.json

@@ -346,7 +346,7 @@
         "description": "crocus: don't map scanout buffers as write-back",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "f3630548f1da904ec6c63b43ece7e68afdb8867e"
     },

src/gallium/drivers/crocus/crocus_bufmgr.c

@@ -430,6 +430,9 @@ bo_alloc_internal(struct crocus_bufmgr *bufmgr,
    bo->index = -1;
    bo->kflags = 0;
 
+   if (flags & BO_ALLOC_SCANOUT)
+      bo->scanout = 1;
+
    if ((flags & BO_ALLOC_COHERENT) && !bo->cache_coherent) {
       struct drm_i915_gem_caching arg = {
          .handle = bo->gem_handle,
@@ -1011,6 +1014,9 @@ crocus_bo_map_gtt(struct pipe_debug_callback *dbg,
 static bool
 can_map_cpu(struct crocus_bo *bo, unsigned flags)
 {
+   if (bo->scanout)
+      return false;
+
    if (bo->cache_coherent)
       return true;
 

src/gallium/drivers/crocus/crocus_bufmgr.h

@@ -141,12 +141,18 @@ struct crocus_bo {
     */
    bool userptr;
 
+   /**
+    * Boolean of if this is used for scanout.
+    */
+   bool scanout;
+
    /** Pre-computed hash using _mesa_hash_pointer for cache tracking sets */
    uint32_t hash;
 };
 
 #define BO_ALLOC_ZEROED   (1 << 0)
 #define BO_ALLOC_COHERENT (1 << 1)
+#define BO_ALLOC_SCANOUT  (1 << 2)
 
 /**
  * Allocate a buffer object.

src/gallium/drivers/crocus/crocus_resource.c

@@ -699,6 +699,10 @@ crocus_resource_create_with_modifiers(struct pipe_screen *pscreen,
    if (templ->usage == PIPE_USAGE_STAGING)
       flags |= BO_ALLOC_COHERENT;
 
+   /* Scanout buffers need to be WC. */
+   if (templ->bind & PIPE_BIND_SCANOUT)
+      flags |= BO_ALLOC_SCANOUT;
+
    uint64_t aux_size = 0;
    uint32_t aux_preferred_alloc_flags;