net: stmmac: Add support for optional reset control

The DWMAC has a reset assert line, which is used on some SoCs. Add an
optional reset control to stmmac driver core.

To support reset control deferred probing, this patch changes the driver
probe function to return the actual error, instead of just -EINVAL.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 0d2c4cb0996b..0c5c1208900e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -51,6 +51,7 @@
 #include <linux/net_tstamp.h>
 #include "stmmac_ptp.h"
 #include "stmmac.h"
+#include <linux/reset.h>
 
 #define STMMAC_ALIGN(x)	L1_CACHE_ALIGN(x)
 #define JUMBO_LEN	9000
@@ -2728,10 +2729,24 @@ struct stmmac_priv *stmmac_dvr_probe(struct device *device,
 	if (IS_ERR(priv->stmmac_clk)) {
 		dev_warn(priv->device, "%s: warning: cannot get CSR clock\n",
 			 __func__);
+		ret = PTR_ERR(priv->stmmac_clk);
 		goto error_clk_get;
 	}
 	clk_prepare_enable(priv->stmmac_clk);
 
+	priv->stmmac_rst = devm_reset_control_get(priv->device,
+						  STMMAC_RESOURCE_NAME);
+	if (IS_ERR(priv->stmmac_rst)) {
+		if (PTR_ERR(priv->stmmac_rst) == -EPROBE_DEFER) {
+			ret = -EPROBE_DEFER;
+			goto error_hw_init;
+		}
+		dev_info(priv->device, "no reset control found\n");
+		priv->stmmac_rst = NULL;
+	}
+	if (priv->stmmac_rst)
+		reset_control_deassert(priv->stmmac_rst);
+
 	/* Init MAC and get the capabilities */
 	ret = stmmac_hw_init(priv);
 	if (ret)
@@ -2808,7 +2823,7 @@ error_hw_init:
 error_clk_get:
 	free_netdev(ndev);
 
-	return NULL;
+	return ERR_PTR(ret);
 }
 
 /**
@@ -2832,6 +2847,8 @@ int stmmac_dvr_remove(struct net_device *ndev)
 		stmmac_mdio_unregister(ndev);
 	netif_carrier_off(ndev);
 	unregister_netdev(ndev);
+	if (priv->stmmac_rst)
+		reset_control_assert(priv->stmmac_rst);
 	clk_disable_unprepare(priv->stmmac_clk);
 	free_netdev(ndev);