drm/i915/guc: Add LRC descriptor context lookup array

Add LRC descriptor context lookup array which can resolve the
intel_context from the LRC descriptor index. In addition to lookup, it
can determine if the LRC descriptor context is currently registered with
the GuC by checking if an entry for a descriptor index is present.
Future patches in the series will make use of this array.

v2:
 (Michal)
  - "linux/xarray.h" -> <linux/xarray.h>
  - s/lrc/LRC
 (John H)
  - Fix commit message

Cc: John Harrison <john.c.harrison@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210721215101.139794-4-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc.h

@@ -6,6 +6,8 @@
 #ifndef _INTEL_GUC_H_
 #define _INTEL_GUC_H_
 
+#include <linux/xarray.h>
+
 #include "intel_uncore.h"
 #include "intel_guc_fw.h"
 #include "intel_guc_fwif.h"
@@ -46,6 +48,9 @@ struct intel_guc {
 	struct i915_vma *lrc_desc_pool;
 	void *lrc_desc_pool_vaddr;
 
+	/* guc_id to intel_context lookup */
+	struct xarray context_lookup;
+
 	/* Control params for fw initialization */
 	u32 params[GUC_CTL_MAX_DWORDS];
 

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -65,8 +65,6 @@ static inline struct i915_priolist *to_priolist(struct rb_node *rb)
 	return rb_entry(rb, struct i915_priolist, node);
 }
 
-/* Future patches will use this function */
-__maybe_unused
 static struct guc_lrc_desc *__get_lrc_desc(struct intel_guc *guc, u32 index)
 {
 	struct guc_lrc_desc *base = guc->lrc_desc_pool_vaddr;
@@ -76,6 +74,15 @@ static struct guc_lrc_desc *__get_lrc_desc(struct intel_guc *guc, u32 index)
 	return &base[index];
 }
 
+static inline struct intel_context *__get_context(struct intel_guc *guc, u32 id)
+{
+	struct intel_context *ce = xa_load(&guc->context_lookup, id);
+
+	GEM_BUG_ON(id >= GUC_MAX_LRC_DESCRIPTORS);
+
+	return ce;
+}
+
 static int guc_lrc_desc_pool_create(struct intel_guc *guc)
 {
 	u32 size;
@@ -96,6 +103,25 @@ static void guc_lrc_desc_pool_destroy(struct intel_guc *guc)
 	i915_vma_unpin_and_release(&guc->lrc_desc_pool, I915_VMA_RELEASE_MAP);
 }
 
+static inline void reset_lrc_desc(struct intel_guc *guc, u32 id)
+{
+	struct guc_lrc_desc *desc = __get_lrc_desc(guc, id);
+
+	memset(desc, 0, sizeof(*desc));
+	xa_erase_irq(&guc->context_lookup, id);
+}
+
+static inline bool lrc_desc_registered(struct intel_guc *guc, u32 id)
+{
+	return __get_context(guc, id);
+}
+
+static inline void set_lrc_desc_registered(struct intel_guc *guc, u32 id,
+					   struct intel_context *ce)
+{
+	xa_store_irq(&guc->context_lookup, id, ce, GFP_ATOMIC);
+}
+
 static void guc_add_request(struct intel_guc *guc, struct i915_request *rq)
 {
 	/* Leaving stub as this function will be used in future patches */
@@ -400,6 +426,8 @@ int intel_guc_submission_init(struct intel_guc *guc)
 	 */
 	GEM_BUG_ON(!guc->lrc_desc_pool);
 
+	xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
+
 	return 0;
 }