net: stmmac: dwxgmac2: Add MAC loopback support

In preparation for the addition of stmmac selftests we implement the MAC
loopback callback in dwxgmac2 core.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h

@@ -29,6 +29,7 @@
 #define XGMAC_CONFIG_GPSL		GENMASK(29, 16)
 #define XGMAC_CONFIG_GPSL_SHIFT		16
 #define XGMAC_CONFIG_S2KP		BIT(11)
+#define XGMAC_CONFIG_LM			BIT(10)
 #define XGMAC_CONFIG_IPC		BIT(9)
 #define XGMAC_CONFIG_JE			BIT(8)
 #define XGMAC_CONFIG_WD			BIT(7)

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c

@@ -321,6 +321,18 @@ static void dwxgmac2_set_filter(struct mac_device_info *hw,
 	writel(value, ioaddr + XGMAC_PACKET_FILTER);
 }
 
+static void dwxgmac2_set_mac_loopback(void __iomem *ioaddr, bool enable)
+{
+	u32 value = readl(ioaddr + XGMAC_RX_CONFIG);
+
+	if (enable)
+		value |= XGMAC_CONFIG_LM;
+	else
+		value &= ~XGMAC_CONFIG_LM;
+
+	writel(value, ioaddr + XGMAC_RX_CONFIG);
+}
+
 const struct stmmac_ops dwxgmac210_ops = {
 	.core_init = dwxgmac2_core_init,
 	.set_mac = dwxgmac2_set_mac,
@@ -350,6 +362,7 @@ const struct stmmac_ops dwxgmac210_ops = {
 	.pcs_get_adv_lp = NULL,
 	.debug = NULL,
 	.set_filter = dwxgmac2_set_filter,
+	.set_mac_loopback = dwxgmac2_set_mac_loopback,
 };
 
 int dwxgmac2_setup(struct stmmac_priv *priv)