drm/xe: Allow userspace to configure CCS mode

Allow user to configure the CCS mode setting through a
'ccs_mode' sysfs interface. Also report the current
CCS mode configuration and number of compute slices
available through this interface.

v2: Rebase, make it platform agnostic
v3: Separte out num_cslices sysfs interface and make
    xe_gt_ccs_mode_sysfs_init() return void
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_gt.c

@@ -378,6 +378,9 @@ static int gt_fw_domain_init(struct xe_gt *gt)
 			 "failed to register engines sysfs directory, err: %d\n",
 			 err);
 
+	/* Initialize CCS mode sysfs after early initialization of HW engines */
+	xe_gt_ccs_mode_sysfs_init(gt);
+
 	err = xe_force_wake_put(gt_to_fw(gt), XE_FW_GT);
 	XE_WARN_ON(err);
 	xe_device_mem_access_put(gt_to_xe(gt));

drivers/gpu/drm/xe/xe_gt_ccs_mode.c

@@ -3,10 +3,13 @@
  * Copyright © 2023 Intel Corporation
  */
 
+#include <drm/drm_managed.h>
+
 #include "regs/xe_gt_regs.h"
 #include "xe_assert.h"
 #include "xe_gt.h"
 #include "xe_gt_ccs_mode.h"
+#include "xe_gt_sysfs.h"
 #include "xe_mmio.h"
 
 static void __xe_gt_apply_ccs_mode(struct xe_gt *gt, u32 num_engines)
@@ -76,3 +79,103 @@ void xe_gt_apply_ccs_mode(struct xe_gt *gt)
 
 	__xe_gt_apply_ccs_mode(gt, gt->ccs_mode);
 }
+
+static ssize_t
+num_cslices_show(struct device *kdev,
+		 struct device_attribute *attr, char *buf)
+{
+	struct xe_gt *gt = kobj_to_gt(&kdev->kobj);
+
+	return sysfs_emit(buf, "%u\n", hweight32(CCS_MASK(gt)));
+}
+
+static DEVICE_ATTR_RO(num_cslices);
+
+static ssize_t
+ccs_mode_show(struct device *kdev,
+	      struct device_attribute *attr, char *buf)
+{
+	struct xe_gt *gt = kobj_to_gt(&kdev->kobj);
+
+	return sysfs_emit(buf, "%u\n", gt->ccs_mode);
+}
+
+static ssize_t
+ccs_mode_store(struct device *kdev, struct device_attribute *attr,
+	       const char *buff, size_t count)
+{
+	struct xe_gt *gt = kobj_to_gt(&kdev->kobj);
+	u32 num_engines, num_slices;
+	int ret;
+
+	ret = kstrtou32(buff, 0, &num_engines);
+	if (ret)
+		return ret;
+
+	/*
+	 * Ensure number of engines specified is valid and there is an
+	 * exact multiple of engines for slices.
+	 */
+	num_slices = hweight32(CCS_MASK(gt));
+	if (!num_engines || num_engines > num_slices || num_slices % num_engines) {
+		xe_gt_dbg(gt, "Invalid compute config, %d engines %d slices\n",
+			  num_engines, num_slices);
+		return -EINVAL;
+	}
+
+	if (gt->ccs_mode != num_engines) {
+		xe_gt_info(gt, "Setting compute mode to %d\n", num_engines);
+		gt->ccs_mode = num_engines;
+		xe_gt_reset_async(gt);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(ccs_mode);
+
+static const struct attribute *gt_ccs_mode_attrs[] = {
+	&dev_attr_ccs_mode.attr,
+	&dev_attr_num_cslices.attr,
+	NULL,
+};
+
+static void xe_gt_ccs_mode_sysfs_fini(struct drm_device *drm, void *arg)
+{
+	struct xe_gt *gt = arg;
+
+	sysfs_remove_files(gt->sysfs, gt_ccs_mode_attrs);
+}
+
+/**
+ * xe_gt_ccs_mode_sysfs_init - Initialize CCS mode sysfs interfaces
+ * @gt: GT structure
+ *
+ * Through a per-gt 'ccs_mode' sysfs interface, the user can enable a fixed
+ * number of compute hardware engines to which the available compute slices
+ * are to be allocated. This user configuration change triggers a gt reset
+ * and it is expected that there are no open drm clients while doing so.
+ * The number of available compute slices is exposed to user through a per-gt
+ * 'num_cslices' sysfs interface.
+ */
+void xe_gt_ccs_mode_sysfs_init(struct xe_gt *gt)
+{
+	struct xe_device *xe = gt_to_xe(gt);
+	int err;
+
+	if (!xe_gt_ccs_mode_enabled(gt))
+		return;
+
+	err = sysfs_create_files(gt->sysfs, gt_ccs_mode_attrs);
+	if (err) {
+		drm_warn(&xe->drm, "Sysfs creation for ccs_mode failed err: %d\n", err);
+		return;
+	}
+
+	err = drmm_add_action_or_reset(&xe->drm, xe_gt_ccs_mode_sysfs_fini, gt);
+	if (err) {
+		sysfs_remove_files(gt->sysfs, gt_ccs_mode_attrs);
+		drm_warn(&xe->drm, "%s: drmm_add_action_or_reset failed, err: %d\n",
+			 __func__, err);
+	}
+}

drivers/gpu/drm/xe/xe_gt_ccs_mode.h

@@ -12,6 +12,7 @@
 #include "xe_platform_types.h"
 
 void xe_gt_apply_ccs_mode(struct xe_gt *gt);
+void xe_gt_ccs_mode_sysfs_init(struct xe_gt *gt);
 
 static inline bool xe_gt_ccs_mode_enabled(const struct xe_gt *gt)
 {