drm/i915/pool: constrain pool objects by mapping type

In a few places we always end up mapping the pool object with the FORCE
constraint(to prevent hitting -EBUSY) which will destroy the cached
mapping if it has a different type. As a simple first step, make the
mapping type part of the pool interface, where the behaviour is to only
give out pool objects which match the requested mapping type.

Suggested-by: Chris Wilson <[e-mail]>
Signed-off-by: Matthew Auld <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>
Signed-off-by: Chris Wilson <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

···
 	int err;
 
 	if (!pool) {
-		pool = intel_gt_get_buffer_pool(engine->gt, PAGE_SIZE);
+		pool = intel_gt_get_buffer_pool(engine->gt, PAGE_SIZE,
+						cache->has_llc ?
+						I915_MAP_WB :
+						I915_MAP_WC);
 		if (IS_ERR(pool))
 			return PTR_ERR(pool);
 	}
···
 	if (err)
 		goto err_pool;
 
-	cmd = i915_gem_object_pin_map(pool->obj,
-				      cache->has_llc ?
-				      I915_MAP_FORCE_WB :
-				      I915_MAP_FORCE_WC);
+	cmd = i915_gem_object_pin_map(pool->obj, pool->type);
 	if (IS_ERR(cmd)) {
 		err = PTR_ERR(cmd);
 		goto err_pool;
···
 		return -EINVAL;
 
 	if (!pool) {
-		pool = intel_gt_get_buffer_pool(eb->engine->gt, len);
+		pool = intel_gt_get_buffer_pool(eb->engine->gt, len,
+						I915_MAP_WB);
 		if (IS_ERR(pool))
 			return PTR_ERR(pool);
 		eb->batch_pool = pool;

drivers/gpu/drm/i915/gem/i915_gem_object_blt.c

···
 	count = div_u64(round_up(vma->size, block_size), block_size);
 	size = (1 + 8 * count) * sizeof(u32);
 	size = round_up(size, PAGE_SIZE);
-	pool = intel_gt_get_buffer_pool(ce->engine->gt, size);
+	pool = intel_gt_get_buffer_pool(ce->engine->gt, size, I915_MAP_WC);
 	if (IS_ERR(pool)) {
 		err = PTR_ERR(pool);
 		goto out_pm;
···
 	if (unlikely(err))
 		goto out_put;
 
-	cmd = i915_gem_object_pin_map(pool->obj, I915_MAP_WC);
+	cmd = i915_gem_object_pin_map(pool->obj, pool->type);
 	if (IS_ERR(cmd)) {
 		err = PTR_ERR(cmd);
 		goto out_unpin;
···
 	count = div_u64(round_up(dst->size, block_size), block_size);
 	size = (1 + 11 * count) * sizeof(u32);
 	size = round_up(size, PAGE_SIZE);
-	pool = intel_gt_get_buffer_pool(ce->engine->gt, size);
+	pool = intel_gt_get_buffer_pool(ce->engine->gt, size, I915_MAP_WC);
 	if (IS_ERR(pool)) {
 		err = PTR_ERR(pool);
 		goto out_pm;
···
 	if (unlikely(err))
 		goto out_put;
 
-	cmd = i915_gem_object_pin_map(pool->obj, I915_MAP_WC);
+	cmd = i915_gem_object_pin_map(pool->obj, pool->type);
 	if (IS_ERR(cmd)) {
 		err = PTR_ERR(cmd);
 		goto out_unpin;

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c

···
 }
 
 static struct intel_gt_buffer_pool_node *
-node_create(struct intel_gt_buffer_pool *pool, size_t sz)
+node_create(struct intel_gt_buffer_pool *pool, size_t sz,
+	    enum i915_map_type type)
 {
 	struct intel_gt *gt = to_gt(pool);
 	struct intel_gt_buffer_pool_node *node;
···
 
 	i915_gem_object_set_readonly(obj);
 
+	node->type = type;
 	node->obj = obj;
 	return node;
 }
 
 struct intel_gt_buffer_pool_node *
-intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size)
+intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size,
+			 enum i915_map_type type)
 {
 	struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 	struct intel_gt_buffer_pool_node *node;
···
 		if (node->obj->base.size < size)
 			continue;
 
+		if (node->type != type)
+			continue;
+
 		age = READ_ONCE(node->age);
 		if (!age)
 			continue;
···
 	rcu_read_unlock();
 
 	if (&node->link == list) {
-		node = node_create(pool, size);
+		node = node_create(pool, size, type);
 		if (IS_ERR(node))
 			return node;
 	}

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.h

···
 struct i915_request;
 
 struct intel_gt_buffer_pool_node *
-intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size);
+intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size,
+			 enum i915_map_type type);
 
 static inline int
 intel_gt_buffer_pool_mark_active(struct intel_gt_buffer_pool_node *node,

drivers/gpu/drm/i915/gt/intel_gt_buffer_pool_types.h

···
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 
+#include "gem/i915_gem_object_types.h"
 #include "i915_active_types.h"
-
-struct drm_i915_gem_object;
 
 struct intel_gt_buffer_pool {
 	spinlock_t lock;
···
 		struct rcu_head rcu;
 	};
 	unsigned long age;
+	enum i915_map_type type;
 };
 
 #endif /* INTEL_GT_BUFFER_POOL_TYPES_H */

drivers/gpu/drm/i915/i915_cmd_parser.c

···
 	void *dst, *src;
 	int ret;
 
-	dst = i915_gem_object_pin_map(dst_obj, I915_MAP_FORCE_WB);
+	dst = i915_gem_object_pin_map(dst_obj, I915_MAP_WB);
 	if (IS_ERR(dst))
 		return dst;