octeontx2-pf: Use hardware register for CQE count

Current driver uses software CQ head pointer to poll on CQE
header in memory to determine if CQE is valid. Software needs
to make sure, that the reads of the CQE do not get re-ordered
so much that it ends up with an inconsistent view of the CQE.
To ensure that DMB barrier after read to first CQE cacheline
and before reading of the rest of the CQE is needed.
But having barrier for every CQE read will impact the performance,
instead use hardware CQ head and tail pointers to find the
valid number of CQEs.

Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c

@@ -1006,6 +1006,9 @@ int otx2_config_nix_queues(struct otx2_nic *pfvf)
 			return err;
 	}
 
+	pfvf->cq_op_addr = (__force u64 *)otx2_get_regaddr(pfvf,
+							   NIX_LF_CQ_OP_STATUS);
+
 	/* Initialize work queue for receive buffer refill */
 	pfvf->refill_wrk = devm_kcalloc(pfvf->dev, pfvf->qset.cq_cnt,
 					sizeof(struct refill_work), GFP_KERNEL);

drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.h

@@ -343,6 +343,7 @@ struct otx2_nic {
 #define OTX2_FLAG_TC_MATCHALL_INGRESS_ENABLED	BIT_ULL(13)
 #define OTX2_FLAG_DMACFLTR_SUPPORT		BIT_ULL(14)
 	u64			flags;
+	u64			*cq_op_addr;
 
 	struct otx2_qset	qset;
 	struct otx2_hw		hw;

drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c

@@ -18,6 +18,31 @@
 
 #define CQE_ADDR(CQ, idx) ((CQ)->cqe_base + ((CQ)->cqe_size * (idx)))
 
+static int otx2_nix_cq_op_status(struct otx2_nic *pfvf,
+				 struct otx2_cq_queue *cq)
+{
+	u64 incr = (u64)(cq->cq_idx) << 32;
+	u64 status;
+
+	status = otx2_atomic64_fetch_add(incr, pfvf->cq_op_addr);
+
+	if (unlikely(status & BIT_ULL(CQ_OP_STAT_OP_ERR) ||
+		     status & BIT_ULL(CQ_OP_STAT_CQ_ERR))) {
+		dev_err(pfvf->dev, "CQ stopped due to error");
+		return -EINVAL;
+	}
+
+	cq->cq_tail = status & 0xFFFFF;
+	cq->cq_head = (status >> 20) & 0xFFFFF;
+	if (cq->cq_tail < cq->cq_head)
+		cq->pend_cqe = (cq->cqe_cnt - cq->cq_head) +
+				cq->cq_tail;
+	else
+		cq->pend_cqe = cq->cq_tail - cq->cq_head;
+
+	return 0;
+}
+
 static struct nix_cqe_hdr_s *otx2_get_next_cqe(struct otx2_cq_queue *cq)
 {
 	struct nix_cqe_hdr_s *cqe_hdr;
@@ -318,7 +343,14 @@ static int otx2_rx_napi_handler(struct otx2_nic *pfvf,
 	struct nix_cqe_rx_s *cqe;
 	int processed_cqe = 0;
 
-	while (likely(processed_cqe < budget)) {
+	if (cq->pend_cqe >= budget)
+		goto process_cqe;
+
+	if (otx2_nix_cq_op_status(pfvf, cq) || !cq->pend_cqe)
+		return 0;
+
+process_cqe:
+	while (likely(processed_cqe < budget) && cq->pend_cqe) {
 		cqe = (struct nix_cqe_rx_s *)CQE_ADDR(cq, cq->cq_head);
 		if (cqe->hdr.cqe_type == NIX_XQE_TYPE_INVALID ||
 		    !cqe->sg.seg_addr) {
@@ -334,6 +366,7 @@ static int otx2_rx_napi_handler(struct otx2_nic *pfvf,
 		cqe->hdr.cqe_type = NIX_XQE_TYPE_INVALID;
 		cqe->sg.seg_addr = 0x00;
 		processed_cqe++;
+		cq->pend_cqe--;
 	}
 
 	/* Free CQEs to HW */
@@ -368,7 +401,14 @@ static int otx2_tx_napi_handler(struct otx2_nic *pfvf,
 	struct nix_cqe_tx_s *cqe;
 	int processed_cqe = 0;
 
-	while (likely(processed_cqe < budget)) {
+	if (cq->pend_cqe >= budget)
+		goto process_cqe;
+
+	if (otx2_nix_cq_op_status(pfvf, cq) || !cq->pend_cqe)
+		return 0;
+
+process_cqe:
+	while (likely(processed_cqe < budget) && cq->pend_cqe) {
 		cqe = (struct nix_cqe_tx_s *)otx2_get_next_cqe(cq);
 		if (unlikely(!cqe)) {
 			if (!processed_cqe)
@@ -380,6 +420,7 @@ static int otx2_tx_napi_handler(struct otx2_nic *pfvf,
 
 		cqe->hdr.cqe_type = NIX_XQE_TYPE_INVALID;
 		processed_cqe++;
+		cq->pend_cqe--;
 	}
 
 	/* Free CQEs to HW */
@@ -936,10 +977,16 @@ void otx2_cleanup_rx_cqes(struct otx2_nic *pfvf, struct otx2_cq_queue *cq)
 	int processed_cqe = 0;
 	u64 iova, pa;
 
-	while ((cqe = (struct nix_cqe_rx_s *)otx2_get_next_cqe(cq))) {
-		if (!cqe->sg.subdc)
-			continue;
+	if (otx2_nix_cq_op_status(pfvf, cq) || !cq->pend_cqe)
+		return;
+
+	while (cq->pend_cqe) {
+		cqe = (struct nix_cqe_rx_s *)otx2_get_next_cqe(cq);
 		processed_cqe++;
+		cq->pend_cqe--;
+
+		if (!cqe)
+			continue;
 		if (cqe->sg.segs > 1) {
 			otx2_free_rcv_seg(pfvf, cqe, cq->cq_idx);
 			continue;
@@ -965,15 +1012,23 @@ void otx2_cleanup_tx_cqes(struct otx2_nic *pfvf, struct otx2_cq_queue *cq)
 
 	sq = &pfvf->qset.sq[cq->cint_idx];
 
-	while ((cqe = (struct nix_cqe_tx_s *)otx2_get_next_cqe(cq))) {
+	if (otx2_nix_cq_op_status(pfvf, cq) || !cq->pend_cqe)
+		return;
+
+	while (cq->pend_cqe) {
+		cqe = (struct nix_cqe_tx_s *)otx2_get_next_cqe(cq);
+		processed_cqe++;
+		cq->pend_cqe--;
+
+		if (!cqe)
+			continue;
 		sg = &sq->sg[cqe->comp.sqe_id];
 		skb = (struct sk_buff *)sg->skb;
 		if (skb) {
 			otx2_dma_unmap_skb_frags(pfvf, sg);
 			dev_kfree_skb_any(skb);
 			sg->skb = (u64)NULL;
 		}
-		processed_cqe++;
 	}
 
 	/* Free CQEs to HW */

drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.h

@@ -56,6 +56,9 @@
  */
 #define CQ_QCOUNT_DEFAULT	1
 
+#define CQ_OP_STAT_OP_ERR       63
+#define CQ_OP_STAT_CQ_ERR       46
+
 struct queue_stats {
 	u64	bytes;
 	u64	pkts;
@@ -122,6 +125,8 @@ struct otx2_cq_queue {
 	u16			pool_ptrs;
 	u32			cqe_cnt;
 	u32			cq_head;
+	u32			cq_tail;
+	u32			pend_cqe;
 	void			*cqe_base;
 	struct qmem		*cqe;
 	struct otx2_pool	*rbpool;

include/linux/soc/marvell/octeontx2/asm.h

@@ -34,9 +34,23 @@
 			 : [rf] "+r"(val)		\
 			 : [rs] "r"(addr));		\
 })
+
+static inline u64 otx2_atomic64_fetch_add(u64 incr, u64 *ptr)
+{
+	u64 result;
+
+	asm volatile (".cpu  generic+lse\n"
+		      "ldadda %x[i], %x[r], [%[b]]"
+		      : [r] "=r" (result), "+m" (*ptr)
+		      : [i] "r" (incr), [b] "r" (ptr)
+		      : "memory");
+	return result;
+}
+
 #else
 #define otx2_lmt_flush(ioaddr)          ({ 0; })
 #define cn10k_lmt_flush(val, addr)	({ addr = val; })
+#define otx2_atomic64_fetch_add(incr, ptr)	({ incr; })
 #endif
 
 #endif /* __SOC_OTX2_ASM_H */