phy: cadence: salvo: add bist fix

Very limited parts may fail to work on full speed mode (both host and
device modes) for USB3 port due to higher threshold in full speed receiver
of USB2.0 PHY.

One example failure symptom is, the enumeration is failed when connecting
full speed USB mouse to USB3 port, especially under high temperature.

The workaround is to configure threshold voltage value of single ended
receiver by setting USB2.0 PHY register AFE_RX_REG5[2:0] to 3'b101.

Signed-off-by: Peter Chen <[email protected]>
Signed-off-by: Frank Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: Peter Chen

drivers/phy/cadence/phy-cadence-salvo.c

@@ -91,6 +91,7 @@
 
 /* USB2 PHY register definition */
 #define UTMI_REG15				0xaf
+#define UTMI_AFE_RX_REG5			0x12
 
 /* TB_ADDR_TX_RCVDETSC_CTRL */
 #define RXDET_IN_P3_32KHZ			BIT(0)
@@ -247,6 +248,7 @@ static int cdns_salvo_phy_init(struct phy *phy)
 	cdns_salvo_write(salvo_phy, USB2_PHY_OFFSET, UTMI_REG15,
 			 value | TXVALID_GATE_THRESHOLD_HS_0US);
 
+	cdns_salvo_write(salvo_phy, USB2_PHY_OFFSET, UTMI_AFE_RX_REG5, 0x5);
 	udelay(10);
 
 	clk_disable_unprepare(salvo_phy->clk);