[PATCH 09/12] drm/xe: Add xe_tlb_inval_idle helper

[Matthew Brost <matthew.brost@intel.com>]

Introduce the xe_tlb_inval_idle helper to detect whether any TLB
invalidations are currently in flight. This is used in context-based TLB
invalidations to determine whether dummy TLB invalidations need to be
sent to maintain proper TLB invalidation fence ordering..

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_tlb_inval.c | 26 ++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_tlb_inval.h |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.c b/drivers/gpu/drm/xe/xe_tlb_inval.c
index 7ee081b94f90..32a0a882343b 100644
--- a/drivers/gpu/drm/xe/xe_tlb_inval.c
+++ b/drivers/gpu/drm/xe/xe_tlb_inval.c
@@ -141,6 +141,7 @@ int xe_gt_tlb_inval_init_early(struct xe_gt *gt)
 
 	tlb_inval->xe = xe;
 	tlb_inval->seqno = 1;
+	tlb_inval->seqno_recv = TLB_INVALIDATION_SEQNO_MAX - 1;
 	INIT_LIST_HEAD(&tlb_inval->pending_fences);
 	spin_lock_init(&tlb_inval->pending_lock);
 	spin_lock_init(&tlb_inval->lock);
@@ -443,3 +444,28 @@ void xe_tlb_inval_fence_init(struct xe_tlb_inval *tlb_inval,
 		dma_fence_get(&fence->base);
 	fence->tlb_inval = tlb_inval;
 }
+
+/**
+ * xe_tlb_inval_idle() - Initialize TLB invalidation is idle
+ * @tlb_inval: TLB invalidation client
+ *
+ * Check the TLB invalidation seqno to determine if it is idle (i.e., no TLB
+ * invalidations are in flight). Expected to be called in the backend after the
+ * seqno has been bumped, and takes this into account.
+ *
+ * Return: True if TLB invalidation client is idle, False otherwise
+ */
+bool xe_tlb_inval_idle(struct xe_tlb_inval *tlb_inval)
+{
+	int next_recv;
+
+	lockdep_assert_held(&tlb_inval->seqno_lock);
+
+	guard(spinlock_irq)(&tlb_inval->pending_lock);
+
+	next_recv = (tlb_inval->seqno_recv + 2) % TLB_INVALIDATION_SEQNO_MAX;
+	if (!next_recv)
+		next_recv = 1;
+
+	return next_recv == tlb_inval->seqno;
+}
diff --git a/drivers/gpu/drm/xe/xe_tlb_inval.h b/drivers/gpu/drm/xe/xe_tlb_inval.h
index 05614915463a..44a6d9177489 100644
--- a/drivers/gpu/drm/xe/xe_tlb_inval.h
+++ b/drivers/gpu/drm/xe/xe_tlb_inval.h
@@ -43,4 +43,6 @@ xe_tlb_inval_fence_wait(struct xe_tlb_inval_fence *fence)
 
 void xe_tlb_inval_done_handler(struct xe_tlb_inval *tlb_inval, int seqno);
 
+bool xe_tlb_inval_idle(struct xe_tlb_inval *tlb_inval);
+
 #endif	/* _XE_TLB_INVAL_ */
-- 
2.34.1