[PATCH net v3] net: airoha: Add dma_rmb() and READ_ONCE() in airoha_qdma_rx_process()

[Lorenzo Bianconi <lorenzo@kernel.org>]

Add missing dma_rmb() in airoha_qdma_rx_process routine to make sure the
DMA read operations are completed when the NIC reports the processing on
the current descriptor is done. Moreover, add missing READ_ONCE() in
airoha_qdma_rx_process() for DMA descriptor control fields in order to
avoid any compiler reordering.

Fixes: 23020f0493270 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
Changes in v3:
- Move page pointer initialization before checking error condition on
  payload length in order avoid using page pointer uninitialized in the
  airoha_qdma_rx_process() error path.
- Link to v2: https://lore.kernel.org/r/20260403-airoha_qdma_rx_process-fix-reordering-v2-1-181e6e23d27b@kernel.org

Changes in v2:
- Use msg1 in airoha_qdma_get_gdm_port() signature to avoid missing
  READ_ONCE().
- Link to v1: https://lore.kernel.org/r/20260402-airoha_qdma_rx_process-fix-reordering-v1-1-53278474f062@kernel.org
---
 drivers/net/ethernet/airoha/airoha_eth.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 91cb63a32d99..9285a68f435f 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -584,7 +584,7 @@ static int airoha_qdma_fill_rx_queue(struct airoha_queue *q)
 static int airoha_qdma_get_gdm_port(struct airoha_eth *eth,
 				    struct airoha_qdma_desc *desc)
 {
-	u32 port, sport, msg1 = le32_to_cpu(desc->msg1);
+	u32 port, sport, msg1 = le32_to_cpu(READ_ONCE(desc->msg1));
 
 	sport = FIELD_GET(QDMA_ETH_RXMSG_SPORT_MASK, msg1);
 	switch (sport) {
@@ -612,21 +612,24 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 	while (done < budget) {
 		struct airoha_queue_entry *e = &q->entry[q->tail];
 		struct airoha_qdma_desc *desc = &q->desc[q->tail];
-		u32 hash, reason, msg1 = le32_to_cpu(desc->msg1);
-		struct page *page = virt_to_head_page(e->buf);
-		u32 desc_ctrl = le32_to_cpu(desc->ctrl);
+		u32 hash, reason, msg1, desc_ctrl;
 		struct airoha_gdm_port *port;
 		int data_len, len, p;
+		struct page *page;
 
+		desc_ctrl = le32_to_cpu(READ_ONCE(desc->ctrl));
 		if (!(desc_ctrl & QDMA_DESC_DONE_MASK))
 			break;
 
+		dma_rmb();
+
 		q->tail = (q->tail + 1) % q->ndesc;
 		q->queued--;
 
 		dma_sync_single_for_cpu(eth->dev, e->dma_addr,
 					SKB_WITH_OVERHEAD(q->buf_size), dir);
 
+		page = virt_to_head_page(e->buf);
 		len = FIELD_GET(QDMA_DESC_LEN_MASK, desc_ctrl);
 		data_len = q->skb ? q->buf_size
 				  : SKB_WITH_OVERHEAD(q->buf_size);
@@ -670,8 +673,8 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 			 * DMA descriptor. Report DSA tag to the DSA stack
 			 * via skb dst info.
 			 */
-			u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG,
-					      le32_to_cpu(desc->msg0));
+			u32 msg0 = le32_to_cpu(READ_ONCE(desc->msg0));
+			u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG, msg0);
 
 			if (sptag < ARRAY_SIZE(port->dsa_meta) &&
 			    port->dsa_meta[sptag])
@@ -679,6 +682,7 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 						  &port->dsa_meta[sptag]->dst);
 		}
 
+		msg1 = le32_to_cpu(READ_ONCE(desc->msg1));
 		hash = FIELD_GET(AIROHA_RXD4_FOE_ENTRY, msg1);
 		if (hash != AIROHA_RXD4_FOE_ENTRY)
 			skb_set_hash(q->skb, jhash_1word(hash, 0),

---
base-commit: a9d4f4f6e65e0bf9bbddedecc84d67249991979c
change-id: 20260402-airoha_qdma_rx_process-fix-reordering-722308255b65

Best regards,
-- 
Lorenzo Bianconi <lorenzo@kernel.org>