net: stmmac: add select_pcs() platform method

Allow platform drivers to provide their logic to select an appropriate
PCS.

Tested-by: Romain Gantois <romain.gantois@bootlin.com>
Reviewed-by: Romain Gantois <romain.gantois@bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1sHhoM-00Fesu-8E@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -949,6 +949,13 @@ static struct phylink_pcs *stmmac_mac_select_pcs(struct phylink_config *config,
 						 phy_interface_t interface)
 {
 	struct stmmac_priv *priv = netdev_priv(to_net_dev(config->dev));
+	struct phylink_pcs *pcs;
+
+	if (priv->plat->select_pcs) {
+		pcs = priv->plat->select_pcs(priv, interface);
+		if (!IS_ERR(pcs))
+			return pcs;
+	}
 
 	if (priv->hw->xpcs)
 		return &priv->hw->xpcs->pcs;

include/linux/stmmac.h

@@ -13,7 +13,7 @@
 #define __STMMAC_PLATFORM_DATA
 
 #include <linux/platform_device.h>
-#include <linux/phy.h>
+#include <linux/phylink.h>
 
 #define MTL_MAX_RX_QUEUES	8
 #define MTL_MAX_TX_QUEUES	8
@@ -271,6 +271,8 @@ struct plat_stmmacenet_data {
 	void (*dump_debug_regs)(void *priv);
 	int (*pcs_init)(struct stmmac_priv *priv);
 	void (*pcs_exit)(struct stmmac_priv *priv);
+	struct phylink_pcs *(*select_pcs)(struct stmmac_priv *priv,
+					  phy_interface_t interface);
 	void *bsp_priv;
 	struct clk *stmmac_clk;
 	struct clk *pclk;