linux-kernel - [PATCH 2/7] phy: rockchip: usbdp: Fix LFPS detect threshold control

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Message-Id: <20260203-rockchip-usbdp-cleanup-v1-2-16a6f92ed176@collabora.com>
Date: Tue, 03 Feb 2026 19:41:28 +0100
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: Vinod Koul <vkoul@...nel.org>, 
 Neil Armstrong <neil.armstrong@...aro.org>, 
 Heiko Stuebner <heiko@...ech.de>
Cc: Andy Yan <andy.yan@...k-chips.com>, 
 Yubing Zhang <yubing.zhang@...k-chips.com>, linux-phy@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, kernel@...labora.com, 
 Sebastian Reichel <sebastian.reichel@...labora.com>, 
 William Wu <william.wu@...k-chips.com>
Subject: [PATCH 2/7] phy: rockchip: usbdp: Fix LFPS detect threshold
 control

From: William Wu <william.wu@...k-chips.com>

According to the LFPS Tx Low Power/LFPS Rx Detect Threshold [1],
the device under test(DUT) must not respond if LFPS below the
minimum LFPS Rx Detect Threshold 100mV. Test fail on Rockchip
platforms, because the default LFPS detect threshold is set to
65mV.

The USBDP PHY LFPS detect threshold voltage could be set to
30mV ~ 140mV, and since there could be 10-20% PVT variation,
we set LFPS detect threshold voltage to 110mV.

[1] https://compliance.usb.org/resources/LFPS_Rx_Tx_Low_Power_Compliance_Update_Rev5.pdf

Signed-off-by: William Wu <william.wu@...k-chips.com>
[Taken over from rockchip's kernel tree; the registers are not described
in the TRM]
Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
---
 drivers/phy/rockchip/phy-rockchip-usbdp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/phy/rockchip/phy-rockchip-usbdp.c b/drivers/phy/rockchip/phy-rockchip-usbdp.c
index b494819be284..7e4142aef192 100644
--- a/drivers/phy/rockchip/phy-rockchip-usbdp.c
+++ b/drivers/phy/rockchip/phy-rockchip-usbdp.c
@@ -413,7 +413,8 @@ static const struct reg_sequence rk_udphy_init_sequence[] = {
 	{0x0070, 0x7d}, {0x0074, 0x68},
 	{0x0af4, 0x1a}, {0x1af4, 0x1a},
 	{0x0440, 0x3f}, {0x10d4, 0x08},
-	{0x20d4, 0x08}, {0x0024, 0x6e}
+	{0x20d4, 0x08}, {0x0024, 0x6e},
+	{0x09c0, 0x0a}, {0x19c0, 0x0a}
 };
 
 static inline int rk_udphy_grfreg_write(struct regmap *base,

-- 
2.51.0