net: airoha: Add missing RX_CPU_IDX() configuration in airoha_qdma_cleanup_rx_queue()

[ Upstream commit 656121b ]

When the descriptor index written in REG_RX_CPU_IDX() is equal to the one
stored in REG_RX_DMA_IDX(), the hw will stop since the QDMA RX ring is
empty.
Add missing REG_RX_CPU_IDX() configuration in airoha_qdma_cleanup_rx_queue
routine during QDMA RX ring cleanup.

Fixes: 514aac3 ("net: airoha: Add missing cleanup bits in airoha_qdma_cleanup_rx_queue()")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260408-airoha-cpu-idx-airoha_qdma_cleanup_rx_queue-v1-1-8efa64844308@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: LorenzoBianconi

drivers/net/ethernet/mediatek/airoha_eth.c

@@ -1641,6 +1641,11 @@ static void airoha_qdma_cleanup_rx_queue(struct airoha_queue *q)
 	}
 
 	q->head = q->tail;
+	/* Set RX_DMA_IDX to RX_CPU_IDX to notify the hw the QDMA RX ring is
+	 * empty.
+	 */
+	airoha_qdma_rmw(qdma, REG_RX_CPU_IDX(qid), RX_RING_CPU_IDX_MASK,
+			FIELD_PREP(RX_RING_CPU_IDX_MASK, q->head));
 	airoha_qdma_rmw(qdma, REG_RX_DMA_IDX(qid), RX_RING_DMA_IDX_MASK,
 			FIELD_PREP(RX_RING_DMA_IDX_MASK, q->tail));
 }