net: sparx5: split sparx5_fdma_{start(),stop()}

The two functions: sparx5_fdma_{start(),stop()} are responsible for a
number of things, namely: allocation and initialization of FDMA buffers,
activation FDMA channels in hardware and activation of the NAPI
instance.

This patch splits the buffer allocation and initialization into init and
deinit functions, and the channel and NAPI activation into start and
stop functions. This serves two purposes: 1) the start() and stop()
functions can be reused for lan969x and 2) prepares for future MTU
change support, where we must be able to stop and start the FDMA
channels and NAPI instance, without free'ing and reallocating the FDMA
buffers.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20250113-sparx5-lan969x-switch-driver-5-v2-2-c468f02fd623@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c

@@ -260,10 +260,6 @@ static int sparx5_fdma_rx_alloc(struct sparx5 *sparx5)
 	fdma_dcbs_init(fdma, FDMA_DCB_INFO_DATAL(fdma->db_size),
 		       FDMA_DCB_STATUS_INTR);
 
-	netif_napi_add_weight(rx->ndev, &rx->napi, sparx5_fdma_napi_callback,
-			      FDMA_WEIGHT);
-	napi_enable(&rx->napi);
-	sparx5_fdma_rx_activate(sparx5, rx);
 	return 0;
 }
 
@@ -410,7 +406,7 @@ static void sparx5_fdma_injection_mode(struct sparx5 *sparx5)
 	}
 }
 
-int sparx5_fdma_start(struct sparx5 *sparx5)
+int sparx5_fdma_init(struct sparx5 *sparx5)
 {
 	int err;
 
@@ -443,24 +439,52 @@ int sparx5_fdma_start(struct sparx5 *sparx5)
 	return err;
 }
 
+int sparx5_fdma_deinit(struct sparx5 *sparx5)
+{
+	sparx5_fdma_stop(sparx5);
+	fdma_free_phys(&sparx5->rx.fdma);
+	fdma_free_phys(&sparx5->tx.fdma);
+
+	return 0;
+}
+
 static u32 sparx5_fdma_port_ctrl(struct sparx5 *sparx5)
 {
 	return spx5_rd(sparx5, FDMA_PORT_CTRL(0));
 }
 
+int sparx5_fdma_start(struct sparx5 *sparx5)
+{
+	struct sparx5_rx *rx = &sparx5->rx;
+
+	netif_napi_add_weight(rx->ndev,
+			      &rx->napi,
+			      sparx5_fdma_napi_callback,
+			      FDMA_WEIGHT);
+
+	napi_enable(&rx->napi);
+
+	sparx5_fdma_rx_activate(sparx5, rx);
+
+	return 0;
+}
+
 int sparx5_fdma_stop(struct sparx5 *sparx5)
 {
+	struct sparx5_rx *rx = &sparx5->rx;
+	struct sparx5_tx *tx = &sparx5->tx;
 	u32 val;
 
-	napi_disable(&sparx5->rx.napi);
+	napi_disable(&rx->napi);
+
 	/* Stop the fdma and channel interrupts */
-	sparx5_fdma_rx_deactivate(sparx5, &sparx5->rx);
-	sparx5_fdma_tx_deactivate(sparx5, &sparx5->tx);
+	sparx5_fdma_rx_deactivate(sparx5, rx);
+	sparx5_fdma_tx_deactivate(sparx5, tx);
+
 	/* Wait for the RX channel to stop */
 	read_poll_timeout(sparx5_fdma_port_ctrl, val,
 			  FDMA_PORT_CTRL_XTR_BUF_IS_EMPTY_GET(val) == 0,
 			  500, 10000, 0, sparx5);
-	fdma_free_phys(&sparx5->rx.fdma);
-	fdma_free_phys(&sparx5->tx.fdma);
+
 	return 0;
 }

drivers/net/ethernet/microchip/sparx5/sparx5_main.c

@@ -792,8 +792,11 @@ static int sparx5_start(struct sparx5 *sparx5)
 					       sparx5_fdma_handler,
 					       0,
 					       "sparx5-fdma", sparx5);
-		if (!err)
-			err = sparx5_fdma_start(sparx5);
+		if (!err) {
+			err = sparx5_fdma_init(sparx5);
+			if (!err)
+				sparx5_fdma_start(sparx5);
+		}
 		if (err)
 			sparx5->fdma_irq = -ENXIO;
 	} else {

drivers/net/ethernet/microchip/sparx5/sparx5_main.h

@@ -436,6 +436,8 @@ int sparx5_manual_injection_mode(struct sparx5 *sparx5);
 void sparx5_port_inj_timer_setup(struct sparx5_port *port);
 
 /* sparx5_fdma.c */
+int sparx5_fdma_init(struct sparx5 *sparx5);
+int sparx5_fdma_deinit(struct sparx5 *sparx5);
 int sparx5_fdma_start(struct sparx5 *sparx5);
 int sparx5_fdma_stop(struct sparx5 *sparx5);
 int sparx5_fdma_xmit(struct sparx5 *sparx5, u32 *ifh, struct sk_buff *skb);