Right now the DRM drivers do not support seamless DP takeover and I'm
I'm not aware of any bootloader implementing this feature either.

In any case this feature would be limited to boards using the USBDP PHY
for a DP or eDP connection instead of the more commonly USB-C connector.
With USB-C's DP AltMode a seamless DP takeover requires handing over the
state of the TCPM state machine from the bootloader to the kernel. This
in turn requires a huge amount of work to keep the state machine
implementations synchronized. It's very unlikely we will see somebody
implementing that in the foreseeable future.

As the current code is obviously buggy and untested, let's simply drop
support for seamless DP takeover. It can be re-implemented cleanly once
somebody adds all missing bits.

Technically the VOP side should be disabled first to avoid data being
send to an unpowered PHY from the running pipeline. As a workaround this
force disables HPD. I'm not sure if this would be good enough, but cannot
test as there is no support in the bootloaders known to me and my test
boards route USBDP to USB-C connectors.

Fixes: 2f70bbddeb45 ("phy: rockchip: add usbdp combo phy driver")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/linux-phy/20260612164107.C7DB21F000E9@smtp.kernel.org/ (local)
Signed-off-by: Sebastian Reichel <redacted>
---
 drivers/phy/rockchip/phy-rockchip-usbdp.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/phy/rockchip/phy-rockchip-usbdp.c b/drivers/phy/rockchip/phy-rockchip-usbdp.c
index 3fc8222fcaec..d73455370113 100644
--- a/drivers/phy/rockchip/phy-rockchip-usbdp.c
+++ b/drivers/phy/rockchip/phy-rockchip-usbdp.c

@@ -926,6 +926,7 @@ static int rk_udphy_parse_lane_mux_data(struct rk_udphy *udphy)
 
 static int rk_udphy_get_initial_status(struct rk_udphy *udphy)
 {
+	const struct rk_udphy_cfg *cfg = udphy->cfgs;
 	int ret;
 	u32 value;
 

@@ -938,10 +939,14 @@ static int rk_udphy_get_initial_status(struct rk_udphy *udphy)
 	rk_udphy_reset_deassert_all(udphy);
 
 	regmap_read(udphy->pma_regmap, CMN_LANE_MUX_AND_EN_OFFSET, &value);
-	if (FIELD_GET(CMN_DP_LANE_MUX_ALL, value) && FIELD_GET(CMN_DP_LANE_EN_ALL, value))
-		udphy->status = UDPHY_MODE_DP;
-	else
-		rk_udphy_disable(udphy);
+	if (FIELD_GET(CMN_DP_LANE_MUX_ALL, value) && FIELD_GET(CMN_DP_LANE_EN_ALL, value)) {
+		dev_info(udphy->dev, "Started with DP PHY pre-enabled; seamless takeover unsupported\n");
+		rk_udphy_grfreg_write(udphy->vogrf, &cfg->vogrfcfg[udphy->id].hpd_trigger, false);
+		/* Wait for VOP side to shut up */
+		msleep(100);
+	}
+
+	rk_udphy_disable(udphy);
 
 	return 0;
 }

-- 
2.53.0