phy: phy-mtk-tphy: add a new reference clock

Usually the digital and analog phys use the same reference clock,
but some platforms have two separate reference clocks for each of
them, so add another optional clock to support them.
In order to keep the clock names consistent with PHY IP's, change
the da_ref for analog phy and ref clock for digital phy.

Signed-off-by: Chunfeng Yun <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

drivers/phy/mediatek/phy-mtk-tphy.c

···
 		struct u2phy_banks u2_banks;
 		struct u3phy_banks u3_banks;
 	};
-	struct clk *ref_clk;	/* reference clock of anolog phy */
+	struct clk *ref_clk;	/* reference clock of (digital) phy */
+	struct clk *da_ref_clk;	/* reference clock of analog phy */
 	u32 index;
 	u8 type;
 	int eye_src;
···
 		return ret;
 	}
 
+	ret = clk_prepare_enable(instance->da_ref_clk);
+	if (ret) {
+		dev_err(tphy->dev, "failed to enable da_ref\n");
+		clk_disable_unprepare(instance->ref_clk);
+		return ret;
+	}
+
 	switch (instance->type) {
 	case PHY_TYPE_USB2:
 		u2_phy_instance_init(tphy, instance);
···
 		u2_phy_instance_exit(tphy, instance);
 
 	clk_disable_unprepare(instance->ref_clk);
+	clk_disable_unprepare(instance->da_ref_clk);
 	return 0;
 }
 
···
 		if (IS_ERR(instance->ref_clk)) {
 			dev_err(dev, "failed to get ref_clk(id-%d)\n", port);
 			retval = PTR_ERR(instance->ref_clk);
+			goto put_child;
+		}
+
+		instance->da_ref_clk =
+			devm_clk_get_optional(&phy->dev, "da_ref");
+		if (IS_ERR(instance->da_ref_clk)) {
+			dev_err(dev, "failed to get da_ref_clk(id-%d)\n", port);
+			retval = PTR_ERR(instance->da_ref_clk);
 			goto put_child;
 		}
 	}