[PATCH 1/1] phy: qualcomm: m31-eusb2: Add register XCFGI_159_152 for SE0 recovery

[Peter Chen]

From: Elson Serrao <elson.serrao@xxxxxxxxxxxxxxxx>

This patch introduces support for the XCFGI_159_152 register to enable a
hardware-based SE0 recovery mechanism in the M31 PHY when operating in
host mode.

During PHY initialization, spurious pulses from external devices can
interfere with speed negotiation, potentially leading to abnormal
behavior. To mitigate this, the M31 PHY provides a fail-safe mechanism
controlled by bit 159 of the XCFGI register.

When XCFG_SE0_TIMEOUT_EN (bit 159) is set, a hardware counter is
activated to monitor the SE0 state. If SE0 persists for more than 2.5 ms
before entering L0 mode, the PHY interprets this as bus inactivity and
resets the state machine to its default state. After transitioning to
L0, the PHY resumes normal operation in accordance with the eUSB
specification.

Signed-off-by: Elson Serrao <elson.serrao@xxxxxxxxxxxxxxxx>
Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxxxxx>
---
 drivers/phy/qualcomm/phy-qcom-m31-eusb2.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c b/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
index 275df38256de..8d954e772585 100644
--- a/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
+++ b/drivers/phy/qualcomm/phy-qcom-m31-eusb2.c
@@ -56,6 +56,9 @@
 #define USB_PHY_XCFGI_7_0		(0x15c)
 #define PLL_LOCK_TIME			GENMASK(1, 0)
 
+#define USB_PHY_XCFGI_159_152		(0x1a8)
+#define SE0_TIMEOUT_EN			BIT(7)
+
 #define M31_EUSB_PHY_INIT_CFG(o, b, v)	\
 {				\
 	.off = o,		\
@@ -88,6 +91,13 @@ static const struct m31_phy_tbl_entry m31_eusb2_setup_tbl[] = {
 };
 
 static const struct m31_phy_tbl_entry m31_eusb_phy_override_tbl[] = {
+	/*
+	 * Set XCFGI[159] to enable SE0 timeout mechanism in M31.
+	 * This enables a counter which will assume bus inactive if
+	 * SE0 is more than 2.5ms and reset the state machine to default
+	 * state.
+	 */
+	M31_EUSB_PHY_INIT_CFG(USB_PHY_XCFGI_159_152, SE0_TIMEOUT_EN, 1),
 	M31_EUSB_PHY_INIT_CFG(USB_PHY_XCFGI_39_32, HSTX_PE, 0),
 	M31_EUSB_PHY_INIT_CFG(USB_PHY_XCFGI_71_64, HSTX_SWING, 7),
 	M31_EUSB_PHY_INIT_CFG(USB_PHY_XCFGI_31_24, HSTX_SLEW, 0),
-- 
2.43.0