net: stmmac: Add MAC loopback callback to HWIF

In preparation for the addition of selftests support for stmmac we add a
new callback to HWIF that can be used to set the controller in loopback
mode.
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>
Cc: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -324,6 +324,8 @@ struct stmmac_ops {
 	int (*flex_pps_config)(void __iomem *ioaddr, int index,
 			       struct stmmac_pps_cfg *cfg, bool enable,
 			       u32 sub_second_inc, u32 systime_flags);
+	/* Loopback for selftests */
+	void (*set_mac_loopback)(void __iomem *ioaddr, bool enable);
 };
 
 #define stmmac_core_init(__priv, __args...) \
@@ -392,6 +394,8 @@ struct stmmac_ops {
 	stmmac_do_callback(__priv, mac, rxp_config, __args)
 #define stmmac_flex_pps_config(__priv, __args...) \
 	stmmac_do_callback(__priv, mac, flex_pps_config, __args)
+#define stmmac_set_mac_loopback(__priv, __args...) \
+	stmmac_do_void_callback(__priv, mac, set_mac_loopback, __args)
 
 /* PTP and HW Timer helpers */
 struct stmmac_hwtimestamp {