phy: mediatek: tphy: add support force phy mode switch

this is used to be compatible with old SoCs, such as mt8195, which shares
t-phy between usb3 and pcie controller, usually, it's default mode is pcie
rc mode, and could use force mode to switch into usb3 mode, because pericfg
layer doesn't provide mode switch, also no efuse or jumper can be used;
Currently, only support switch from default pcie mode to usb3;
Note: don't use this way on new SoCs, use pericfg layer's mode switch
instead (by perperty "mediatek,syscon-type").

Signed-off-by: Chunfeng Yun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

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

···
 #define P3D_RG_CDR_BIR_LTD1		GENMASK(28, 24)
 #define P3D_RG_CDR_BIR_LTD0		GENMASK(12, 8)
 
+#define U3P_U3_PHYD_TOP1		0x100
+#define P3D_RG_PHY_MODE			GENMASK(2, 1)
+#define P3D_RG_FORCE_PHY_MODE		BIT(0)
+
 #define U3P_U3_PHYD_RXDET1		0x128
 #define P3D_RG_RXDET_STB2_SET		GENMASK(17, 9)
 
···
 	int discth;
 	int pre_emphasis;
 	bool bc12_en;
+	bool type_force_mode;
 };
 
 struct mtk_tphy {
···
 	void __iomem *phya = u3_banks->phya;
 	void __iomem *phyd = u3_banks->phyd;
 
+	if (instance->type_force_mode) {
+		/* force phy as usb mode, default is pcie rc mode */
+		mtk_phy_update_field(phyd + U3P_U3_PHYD_TOP1, P3D_RG_PHY_MODE, 1);
+		mtk_phy_set_bits(phyd + U3P_U3_PHYD_TOP1, P3D_RG_FORCE_PHY_MODE);
+		/* power down phy by ip and pipe reset */
+		mtk_phy_set_bits(u3_banks->chip + U3P_U3_CHIP_GPIO_CTLD,
+				 P3C_FORCE_IP_SW_RST | P3C_MCU_BUS_CK_GATE_EN);
+		mtk_phy_set_bits(u3_banks->chip + U3P_U3_CHIP_GPIO_CTLE,
+				 P3C_RG_SWRST_U3_PHYD | P3C_RG_SWRST_U3_PHYD_FORCE_EN);
+		udelay(10);
+		/* power on phy again */
+		mtk_phy_clear_bits(u3_banks->chip + U3P_U3_CHIP_GPIO_CTLD,
+				   P3C_FORCE_IP_SW_RST | P3C_MCU_BUS_CK_GATE_EN);
+		mtk_phy_clear_bits(u3_banks->chip + U3P_U3_CHIP_GPIO_CTLE,
+				   P3C_RG_SWRST_U3_PHYD | P3C_RG_SWRST_U3_PHYD_FORCE_EN);
+	}
+
 	/* gating PCIe Analog XTAL clock */
 	mtk_phy_set_bits(u3_banks->spllc + U3P_SPLLC_XTALCTL3,
 			 XC3_RG_U3_XTAL_RX_PWD | XC3_RG_U3_FRC_XTAL_RX_PWD);
···
 				struct mtk_phy_instance *instance)
 {
 	struct device *dev = &instance->phy->dev;
+
+	if (instance->type == PHY_TYPE_USB3)
+		instance->type_force_mode = device_property_read_bool(dev, "mediatek,force-mode");
 
 	if (instance->type != PHY_TYPE_USB2)
 		return;