[PATCH net-next v4 1/2] net: airoha: refactor QDMA start/stop into reusable helpers

[Lorenzo Bianconi <lorenzo@kernel.org>]

Factor out airoha_qdma_start() and airoha_qdma_stop() from
airoha_dev_open() and airoha_dev_stop(). These helpers will be reused
by the QDMA hot-migration logic introduced in the next patch to
dynamically switch GDM3/GDM4 ports between LAN and WAN QDMA blocks.
Add a DMA engine busy poll in airoha_qdma_stop() to wait for in-flight
DMA transfers to complete before cleaning up TX queues.

Tested-by: Madhur Agrawal <madhur.agrawal@airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 53 ++++++++++++++++++++++----------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 5a8e84fa9918..aeac66df5f3b 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -1771,6 +1771,40 @@ static void airoha_update_hw_stats(struct airoha_gdm_dev *dev)
 	spin_unlock(&port->stats.lock);
 }
 
+static void airoha_qdma_start(struct airoha_qdma *qdma)
+{
+	airoha_qdma_set(qdma, REG_QDMA_GLOBAL_CFG,
+			GLOBAL_CFG_TX_DMA_EN_MASK |
+			GLOBAL_CFG_RX_DMA_EN_MASK);
+	atomic_inc(&qdma->users);
+}
+
+static void airoha_qdma_stop(struct airoha_qdma *qdma)
+{
+	u32 status;
+
+	if (!atomic_dec_and_test(&qdma->users))
+		return;
+
+	airoha_qdma_clear(qdma, REG_QDMA_GLOBAL_CFG,
+			  GLOBAL_CFG_TX_DMA_EN_MASK |
+			  GLOBAL_CFG_RX_DMA_EN_MASK);
+
+	if (read_poll_timeout(airoha_qdma_rr, status,
+			      !(status & (GLOBAL_CFG_TX_DMA_BUSY_MASK |
+					  GLOBAL_CFG_RX_DMA_BUSY_MASK)),
+			      USEC_PER_MSEC, 50 * USEC_PER_MSEC, true,
+			      qdma, REG_QDMA_GLOBAL_CFG))
+		dev_warn(qdma->eth->dev, "QDMA DMA engine busy timeout\n");
+
+	for (int i = 0; i < ARRAY_SIZE(qdma->q_tx); i++) {
+		if (!qdma->q_tx[i].ndesc)
+			continue;
+
+		airoha_qdma_cleanup_tx_queue(&qdma->q_tx[i]);
+	}
+}
+
 static int airoha_dev_open(struct net_device *netdev)
 {
 	int err, len = ETH_HLEN + netdev->mtu + ETH_FCS_LEN;
@@ -1806,10 +1840,7 @@ static int airoha_dev_open(struct net_device *netdev)
 	}
 	port->users++;
 
-	airoha_qdma_set(qdma, REG_QDMA_GLOBAL_CFG,
-			GLOBAL_CFG_TX_DMA_EN_MASK |
-			GLOBAL_CFG_RX_DMA_EN_MASK);
-	atomic_inc(&qdma->users);
+	airoha_qdma_start(qdma);
 
 	if (!airoha_is_lan_gdm_dev(dev) &&
 	    airoha_ppe_is_enabled(qdma->eth, 1))
@@ -1862,19 +1893,7 @@ static int airoha_dev_stop(struct net_device *netdev)
 		airoha_set_gdm_port_fwd_cfg(qdma->eth,
 					    REG_GDM_FWD_CFG(port->id),
 					    FE_PSE_PORT_DROP);
-
-	if (atomic_dec_and_test(&qdma->users)) {
-		airoha_qdma_clear(qdma, REG_QDMA_GLOBAL_CFG,
-				  GLOBAL_CFG_TX_DMA_EN_MASK |
-				  GLOBAL_CFG_RX_DMA_EN_MASK);
-
-		for (i = 0; i < ARRAY_SIZE(qdma->q_tx); i++) {
-			if (!qdma->q_tx[i].ndesc)
-				continue;
-
-			airoha_qdma_cleanup_tx_queue(&qdma->q_tx[i]);
-		}
-	}
+	airoha_qdma_stop(qdma);
 
 	return 0;
 }

-- 
2.54.0