net: xilinx: axiethernet: Enable dynamic MDIO MDC

MDIO spec does not require an MDC at all times, only when MDIO
transactions are occurring. This patch allows the xilinx_axienet
driver to disable the MDC when not in use, and re-enable it when
needed. It also simplifies the driver by removing MDC disable
and enable in device reset sequence.
Signed-off-by: Clayton Rayment <clayton.rayment@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/xilinx/xilinx_axienet_main.c

@@ -1049,20 +1049,13 @@ static int axienet_open(struct net_device *ndev)
 
 	dev_dbg(&ndev->dev, "axienet_open()\n");
 
-	/* Disable the MDIO interface till Axi Ethernet Reset is completed.
-	 * When we do an Axi Ethernet reset, it resets the complete core
-	 * including the MDIO. MDIO must be disabled before resetting
-	 * and re-enabled afterwards.
+	/* When we do an Axi Ethernet reset, it resets the complete core
+	 * including the MDIO. MDIO must be disabled before resetting.
 	 * Hold MDIO bus lock to avoid MDIO accesses during the reset.
 	 */
 	mutex_lock(&lp->mii_bus->mdio_lock);
-	axienet_mdio_disable(lp);
 	ret = axienet_device_reset(ndev);
-	if (ret == 0)
-		ret = axienet_mdio_enable(lp);
 	mutex_unlock(&lp->mii_bus->mdio_lock);
-	if (ret < 0)
-		return ret;
 
 	ret = phylink_of_phy_connect(lp->phylink, lp->dev->of_node, 0);
 	if (ret) {
@@ -1156,9 +1149,7 @@ static int axienet_stop(struct net_device *ndev)
 
 	/* Do a reset to ensure DMA is really stopped */
 	mutex_lock(&lp->mii_bus->mdio_lock);
-	axienet_mdio_disable(lp);
 	__axienet_device_reset(lp);
-	axienet_mdio_enable(lp);
 	mutex_unlock(&lp->mii_bus->mdio_lock);
 
 	cancel_work_sync(&lp->dma_err_task);
@@ -1669,16 +1660,12 @@ static void axienet_dma_err_handler(struct work_struct *work)
 
 	axienet_setoptions(ndev, lp->options &
 			   ~(XAE_OPTION_TXEN | XAE_OPTION_RXEN));
-	/* Disable the MDIO interface till Axi Ethernet Reset is completed.
-	 * When we do an Axi Ethernet reset, it resets the complete core
-	 * including the MDIO. MDIO must be disabled before resetting
-	 * and re-enabled afterwards.
+	/* When we do an Axi Ethernet reset, it resets the complete core
+	 * including the MDIO. MDIO must be disabled before resetting.
 	 * Hold MDIO bus lock to avoid MDIO accesses during the reset.
 	 */
 	mutex_lock(&lp->mii_bus->mdio_lock);
-	axienet_mdio_disable(lp);
 	__axienet_device_reset(lp);
-	axienet_mdio_enable(lp);
 	mutex_unlock(&lp->mii_bus->mdio_lock);
 
 	for (i = 0; i < lp->tx_bd_num; i++) {

drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c

@@ -65,9 +65,13 @@ static int axienet_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 	int ret;
 	struct axienet_local *lp = bus->priv;
 
+	axienet_mdio_mdc_enable(lp);
+
 	ret = axienet_mdio_wait_until_ready(lp);
-	if (ret < 0)
+	if (ret < 0) {
+		axienet_mdio_mdc_disable(lp);
 		return ret;
+	}
 
 	axienet_iow(lp, XAE_MDIO_MCR_OFFSET,
 		    (((phy_id << XAE_MDIO_MCR_PHYAD_SHIFT) &
@@ -78,14 +82,17 @@ static int axienet_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 		     XAE_MDIO_MCR_OP_READ_MASK));
 
 	ret = axienet_mdio_wait_until_ready(lp);
-	if (ret < 0)
+	if (ret < 0) {
+		axienet_mdio_mdc_disable(lp);
 		return ret;
+	}
 
 	rc = axienet_ior(lp, XAE_MDIO_MRD_OFFSET) & 0x0000FFFF;
 
 	dev_dbg(lp->dev, "axienet_mdio_read(phy_id=%i, reg=%x) == %x\n",
 		phy_id, reg, rc);
 
+	axienet_mdio_mdc_disable(lp);
 	return rc;
 }
 
@@ -111,9 +118,13 @@ static int axienet_mdio_write(struct mii_bus *bus, int phy_id, int reg,
 	dev_dbg(lp->dev, "axienet_mdio_write(phy_id=%i, reg=%x, val=%x)\n",
 		phy_id, reg, val);
 
+	axienet_mdio_mdc_enable(lp);
+
 	ret = axienet_mdio_wait_until_ready(lp);
-	if (ret < 0)
+	if (ret < 0) {
+		axienet_mdio_mdc_disable(lp);
 		return ret;
+	}
 
 	axienet_iow(lp, XAE_MDIO_MWD_OFFSET, (u32) val);
 	axienet_iow(lp, XAE_MDIO_MCR_OFFSET,
@@ -125,8 +136,11 @@ static int axienet_mdio_write(struct mii_bus *bus, int phy_id, int reg,
 		     XAE_MDIO_MCR_OP_WRITE_MASK));
 
 	ret = axienet_mdio_wait_until_ready(lp);
-	if (ret < 0)
+	if (ret < 0) {
+		axienet_mdio_mdc_disable(lp);
 		return ret;
+	}
+	axienet_mdio_mdc_disable(lp);
 	return 0;
 }
 
@@ -230,8 +244,8 @@ void axienet_mdio_disable(struct axienet_local *lp)
  * Return:	0 on success, -ETIMEDOUT on a timeout, -ENOMEM when
  *		mdiobus_alloc (to allocate memory for mii bus structure) fails.
  *
- * Sets up the MDIO interface by initializing the MDIO clock and enabling the
- * MDIO interface in hardware. Register the MDIO interface.
+ * Sets up the MDIO interface by initializing the MDIO clock.
+ * Register the MDIO interface.
  **/
 int axienet_mdio_setup(struct axienet_local *lp)
 {
@@ -265,6 +279,7 @@ int axienet_mdio_setup(struct axienet_local *lp)
 		lp->mii_bus = NULL;
 		return ret;
 	}
+	axienet_mdio_mdc_disable(lp);
 	return 0;
 }