[PATCH 6/6] drm/xe/xe_guc_ct: Justify WRITE_ONCE/READ_ONCE usage

[Jonathan Cavitt <jonathan.cavitt@intel.com>]

Usage of READ_ONCE and WRITE_ONCE requires comments justifying it.
Some recently added uses had cross-dependencies with each other, but
needed to be added separately, so introduce the justifications now when
it makes more sense to.

Suggested-by: Matthew Brost <matthew.brost@intel.com>
Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
---
 drivers/gpu/drm/xe/xe_guc_ct.c | 5 +++++
 drivers/gpu/drm/xe/xe_guc_ct.h | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index 20ac0438ffb6..24857c2c8cb5 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -529,6 +529,11 @@ static void guc_ct_change_state(struct xe_guc_ct *ct,
 	if (ct->g2h_outstanding)
 		xe_pm_runtime_put(ct_to_xe(ct));
 	ct->g2h_outstanding = 0;
+
+	/*
+	 * WRITE_ONCE pairs with READ_ONCEs in xe_guc_ct_initialized and
+	 * xe_guc_ct_enabled.
+	 */
 	WRITE_ONCE(ct->state, state);
 
 	xe_gt_dbg(gt, "GuC CT communication channel %s\n",
diff --git a/drivers/gpu/drm/xe/xe_guc_ct.h b/drivers/gpu/drm/xe/xe_guc_ct.h
index cb1335f1d66f..8d318b094f33 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.h
+++ b/drivers/gpu/drm/xe/xe_guc_ct.h
@@ -30,11 +30,13 @@ void xe_guc_ct_print(struct xe_guc_ct *ct, struct drm_printer *p, bool want_ctb)
 
 static inline bool xe_guc_ct_initialized(struct xe_guc_ct *ct)
 {
+	/* READ_ONCE pairs with WRITE_ONCE in guc_ct_change_state */
 	return READ_ONCE(ct->state) != XE_GUC_CT_STATE_NOT_INITIALIZED;
 }
 
 static inline bool xe_guc_ct_enabled(struct xe_guc_ct *ct)
 {
+	/* READ_ONCE pairs with WRITE_ONCE in guc_ct_change_state */
 	return READ_ONCE(ct->state) == XE_GUC_CT_STATE_ENABLED;
 }
 
-- 
2.43.0