ravb: Add reset support

Reset support is present on R-Car. Let's support it, if it is
available.
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/ravb.h

@@ -1057,6 +1057,7 @@ struct ravb_private {
 	unsigned int num_tx_desc;	/* TX descriptors per packet */
 
 	const struct ravb_hw_info *info;
+	struct reset_control *rstc;
 };
 
 static inline u32 ravb_read(struct net_device *ndev, enum ravb_reg reg)

drivers/net/ethernet/renesas/ravb_main.c

@@ -29,6 +29,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/sys_soc.h>
+#include <linux/reset.h>
 
 #include <asm/div64.h>
 
@@ -2140,6 +2141,7 @@ static int ravb_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	const struct ravb_hw_info *info;
+	struct reset_control *rstc;
 	struct ravb_private *priv;
 	struct net_device *ndev;
 	int error, irq, q;
@@ -2152,6 +2154,11 @@ static int ravb_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(rstc))
+		return dev_err_probe(&pdev->dev, PTR_ERR(rstc),
+				     "failed to get cpg reset\n");
+
 	ndev = alloc_etherdev_mqs(sizeof(struct ravb_private),
 				  NUM_TX_QUEUE, NUM_RX_QUEUE);
 	if (!ndev)
@@ -2162,6 +2169,7 @@ static int ravb_probe(struct platform_device *pdev)
 	ndev->features = info->net_features;
 	ndev->hw_features = info->net_hw_features;
 
+	reset_control_deassert(rstc);
 	pm_runtime_enable(&pdev->dev);
 	pm_runtime_get_sync(&pdev->dev);
 
@@ -2179,6 +2187,7 @@ static int ravb_probe(struct platform_device *pdev)
 
 	priv = netdev_priv(ndev);
 	priv->info = info;
+	priv->rstc = rstc;
 	priv->ndev = ndev;
 	priv->pdev = pdev;
 	priv->num_tx_ring[RAVB_BE] = BE_TX_RING_SIZE;
@@ -2349,6 +2358,7 @@ static int ravb_probe(struct platform_device *pdev)
 
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+	reset_control_assert(rstc);
 	return error;
 }
 
@@ -2374,6 +2384,7 @@ static int ravb_remove(struct platform_device *pdev)
 	netif_napi_del(&priv->napi[RAVB_BE]);
 	ravb_mdio_release(priv);
 	pm_runtime_disable(&pdev->dev);
+	reset_control_assert(priv->rstc);
 	free_netdev(ndev);
 	platform_set_drvdata(pdev, NULL);