[PATCH v2 2/2] drm/xe: Mutual exclusivity between CCS-mode and PF

[Nareshkumar Gollakoti <naresh.kumar.g@intel.com>]

Due to SLA agreement between PF and VFs,the alternate CCS-mode
cannot be changed when VFs are already enabled.
Similarly, enabling VFs is not permitted when the alternate
CCS-mode is active.

Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com>
---
 drivers/gpu/drm/xe/xe_gt_ccs_mode.c | 37 ++++++++++++++++++-----------
 drivers/gpu/drm/xe/xe_gt_ccs_mode.h | 12 ++++++++++
 2 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
index e146e00b0ca2..52285a550f34 100644
--- a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
+++ b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
@@ -13,6 +13,7 @@
 #include "xe_gt_sysfs.h"
 #include "xe_mmio.h"
 #include "xe_sriov.h"
+#include "xe_sriov_pf.h"
 
 static void __xe_gt_apply_ccs_mode(struct xe_gt *gt, u32 num_engines)
 {
@@ -117,12 +118,6 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
 	u32 num_engines, num_slices;
 	int ret;
 
-	if (IS_SRIOV(xe)) {
-		xe_gt_dbg(gt, "Can't change compute mode when running as %s\n",
-			  xe_sriov_mode_to_string(xe_device_sriov_mode(xe)));
-		return -EOPNOTSUPP;
-	}
-
 	ret = kstrtou32(buff, 0, &num_engines);
 	if (ret)
 		return ret;
@@ -139,21 +134,35 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
 	}
 
 	/* CCS mode can only be updated when there are no drm clients */
-	mutex_lock(&xe->drm.filelist_mutex);
+	guard(mutex)(&xe->drm.filelist_mutex);
 	if (!list_empty(&xe->drm.filelist)) {
-		mutex_unlock(&xe->drm.filelist_mutex);
 		xe_gt_dbg(gt, "Rejecting compute mode change as there are active drm clients\n");
 		return -EBUSY;
 	}
 
-	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_record_user_engines(gt);
-		xe_gt_reset(gt);
+	if (gt->ccs_mode == num_engines)
+		return count;
+
+	/*
+	 * Changing default CCS mode is only allowed when there
+	 * are no VFs. Try to lockdown PF to find out.
+	 */
+	if (xe_gt_ccs_mode_default(gt) && IS_SRIOV_PF(xe)) {
+		ret = xe_sriov_pf_lockdown(xe);
+		if (ret) {
+			xe_gt_dbg(gt, "Can't change CCS Mode: VFs are enabled\n");
+			return ret;
+		}
 	}
 
-	mutex_unlock(&xe->drm.filelist_mutex);
+	xe_gt_info(gt, "Setting compute mode to %d\n", num_engines);
+	gt->ccs_mode = num_engines;
+	xe_gt_record_user_engines(gt);
+	xe_gt_reset(gt);
+
+	/* We may end PF lockdown once CCS mode is default again */
+	if (xe_gt_ccs_mode_default(gt) && IS_SRIOV_PF(xe))
+		xe_sriov_pf_end_lockdown(xe);
 
 	return count;
 }
diff --git a/drivers/gpu/drm/xe/xe_gt_ccs_mode.h b/drivers/gpu/drm/xe/xe_gt_ccs_mode.h
index f8779852cf0d..53a595b0882c 100644
--- a/drivers/gpu/drm/xe/xe_gt_ccs_mode.h
+++ b/drivers/gpu/drm/xe/xe_gt_ccs_mode.h
@@ -20,5 +20,17 @@ static inline bool xe_gt_ccs_mode_enabled(const struct xe_gt *gt)
 	return hweight32(CCS_MASK(gt)) > 1;
 }
 
+/**
+ * xe_gt_ccs_mode_default() - Check if CCS mode is default (single CCS mode)
+ * @gt: GT structure
+ *
+ * Return: %true if actual CCS mode is single mode, or
+ *         %false otherwise (CCS in alternate/multi mode)
+ */
+static inline bool xe_gt_ccs_mode_default(struct xe_gt *gt)
+{
+	return gt->ccs_mode == 1;
+}
+
 #endif
 
-- 
2.43.0