drm/xe/gt: Add APIs for printing stats over debugfs

Add skeleton APIs for recording and printing various stats over
debugfs. This currently only added counter types stats which is backed
by atomic_t and wrapped with CONFIG_DRM_XE_STATS so this can be disabled
on production system.

v4: Rebase and other minor fixes (Matt)
v3: s/CONFIG_DRM_XE_STATS/CONFIG_DEBUG_FS(Lucas)
v2: add missing docs
    Add boundary checks for stats id and other improvements (Michal)
    Fix build when CONFIG_DRM_XE_STATS is disabled(Matt)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sai Gowtham Ch <sai.gowtham.ch@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240810191522.18616-1-nirmoy.das@intel.com
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>

drivers/gpu/drm/xe/Makefile

@@ -277,6 +277,7 @@ ifeq ($(CONFIG_DEBUG_FS),y)
 	xe-y += xe_debugfs.o \
 		xe_gt_debugfs.o \
 		xe_gt_sriov_vf_debugfs.o \
+		xe_gt_stats.o \
 		xe_guc_debugfs.o \
 		xe_huc_debugfs.o \
 		xe_uc_debugfs.o

drivers/gpu/drm/xe/xe_gt_debugfs.c

@@ -17,6 +17,7 @@
 #include "xe_gt_mcr.h"
 #include "xe_gt_sriov_pf_debugfs.h"
 #include "xe_gt_sriov_vf_debugfs.h"
+#include "xe_gt_stats.h"
 #include "xe_gt_topology.h"
 #include "xe_hw_engine.h"
 #include "xe_lrc.h"
@@ -286,6 +287,7 @@ static const struct drm_info_list debugfs_list[] = {
 	{"default_lrc_bcs", .show = xe_gt_debugfs_simple_show, .data = bcs_default_lrc},
 	{"default_lrc_vcs", .show = xe_gt_debugfs_simple_show, .data = vcs_default_lrc},
 	{"default_lrc_vecs", .show = xe_gt_debugfs_simple_show, .data = vecs_default_lrc},
+	{"stats", .show = xe_gt_debugfs_simple_show, .data = xe_gt_stats_print_info},
 };
 
 void xe_gt_debugfs_register(struct xe_gt *gt)

drivers/gpu/drm/xe/xe_gt_stats.c

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include <linux/atomic.h>
+
+#include <drm/drm_print.h>
+
+#include "xe_gt.h"
+#include "xe_gt_stats.h"
+
+/**
+ * xe_gt_stats_incr - Increments the specified stats counter
+ * @gt: graphics tile
+ * @id: xe_gt_stats_id type id that needs to be incremented
+ * @incr: value to be incremented with
+ *
+ * Increments the specified stats counter.
+ */
+void xe_gt_stats_incr(struct xe_gt *gt, const enum xe_gt_stats_id id, int incr)
+{
+	if (id >= __XE_GT_STATS_NUM_IDS)
+		return;
+
+	atomic_add(incr, &gt->stats.counters[id]);
+}
+
+static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
+};
+
+/**
+ * xe_gt_stats_print_info - Print the GT stats
+ * @gt: graphics tile
+ * @p: drm_printer where it will be printed out.
+ *
+ * This prints out all the available GT stats.
+ */
+int xe_gt_stats_print_info(struct xe_gt *gt, struct drm_printer *p)
+{
+	enum xe_gt_stats_id id;
+
+	for (id = 0; id < __XE_GT_STATS_NUM_IDS; ++id)
+		drm_printf(p, "%s: %d\n", stat_description[id],
+			   atomic_read(&gt->stats.counters[id]));
+
+	return 0;
+}

drivers/gpu/drm/xe/xe_gt_stats.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _XE_GT_STATS_H_
+#define _XE_GT_STATS_H_
+
+struct xe_gt;
+struct drm_printer;
+
+enum xe_gt_stats_id {
+	/* must be the last entry */
+	__XE_GT_STATS_NUM_IDS,
+};
+
+#ifdef CONFIG_DEBUG_FS
+int xe_gt_stats_print_info(struct xe_gt *gt, struct drm_printer *p);
+void xe_gt_stats_incr(struct xe_gt *gt, const enum xe_gt_stats_id id, int incr);
+#else
+static inline void
+xe_gt_stats_incr(struct xe_gt *gt, const enum xe_gt_stats_id id,
+		 int incr)
+{
+}
+
+#endif
+#endif

drivers/gpu/drm/xe/xe_gt_types.h

@@ -10,6 +10,7 @@
 #include "xe_gt_idle_types.h"
 #include "xe_gt_sriov_pf_types.h"
 #include "xe_gt_sriov_vf_types.h"
+#include "xe_gt_stats.h"
 #include "xe_hw_engine_types.h"
 #include "xe_hw_fence_types.h"
 #include "xe_oa.h"
@@ -133,6 +134,14 @@ struct xe_gt {
 		u8 has_indirect_ring_state:1;
 	} info;
 
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+	/** @stats: GT stats */
+	struct {
+		/** @stats.counters: counters for various GT stats */
+		atomic_t counters[__XE_GT_STATS_NUM_IDS];
+	} stats;
+#endif
+
 	/**
 	 * @mmio: mmio info for GT.  All GTs within a tile share the same
 	 * register space, but have their own copy of GSI registers at a