The USB OTG port of the RK3308 exibits a bug when:
- configured as peripheral, and - used in gadget mode, and - the USB cable is connected since before booting
The symptom is: about 6 seconds after configuring gadget mode the device is disconnected and then re-enumerated. This happens only once per boot.
Investigation showed that in this configuration the charger detection code turns off the PHY after 6 seconds. Patch 1 avoids this when a cable is connected (VBUS present).
After patch 1 the connection is stable but communication stops after 6 seconds. this is addressed by patch 2.
The topic had been discussed in [0]. Thanks Alan and Minas for the discussion and Louis for having found the 1st issue, leading to patch 1.
[0] https://lore.kernel.org/lkml/20250414185458.7767aabc@booty/
Luca
Signed-off-by: Luca Ceresoli luca.ceresoli@bootlin.com --- Changes in v2: - Patch 1: Fixed Co-developed-by: and SoB line order - Added missing Cc: stable@vger.kernel.org - Added Théo's Reviewed-by - Improved commit message - Patch 2: trimmed discussion about "there is no disconnection" from commit message to not distract from the actual issue (writes to chg_det.opmode) - Link to v1: https://lore.kernel.org/r/20250722-rk3308-fix-usb-gadget-phy-disconnect-v1-0...
--- Louis Chauvet (1): phy: rockchip: inno-usb2: fix disconnection in gadget mode
Luca Ceresoli (1): phy: rockchip: inno-usb2: fix communication disruption in gadget mode
drivers/phy/rockchip/phy-rockchip-inno-usb2.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- base-commit: cabb748c4b98ef67bbb088be61a2e0c850ebf70d change-id: 20250718-rk3308-fix-usb-gadget-phy-disconnect-d7de71fb28b4
Best regards,
From: Louis Chauvet louis.chauvet@bootlin.com
When the OTG USB port is used to power the SoC, configured as peripheral and used in gadget mode, there is a disconnection about 6 seconds after the gadget is configured and enumerated.
The problem was observed on a Radxa Rock Pi S board, which can only be powered by the only USB-C connector. That connector is the only one usable in gadget mode. This implies the USB cable is connected from before boot and never disconnects while the kernel runs.
The problem happens because of the PHY driver code flow, summarized as:
* UDC start code (triggered via configfs at any time after boot) -> phy_init -> rockchip_usb2phy_init -> schedule_delayed_work(otg_sm_work [A], 6 sec) -> phy_power_on -> rockchip_usb2phy_power_on -> enable clock -> rockchip_usb2phy_reset
* Now the gadget interface is up and running.
* 6 seconds later otg_sm_work starts [A] -> rockchip_usb2phy_otg_sm_work(): if (B_IDLE state && VBUS present && ...): schedule_delayed_work(&rport->chg_work [B], 0);
* immediately the chg_detect_work starts [B] -> rockchip_chg_detect_work(): if chg_state is UNDEFINED: if (!rport->suspended): rockchip_usb2phy_power_off() <--- [X]
At [X], the PHY is powered off, causing a disconnection. This quickly triggers a new connection and following re-enumeration, but any connection that had been established during the 6 seconds is broken.
The code already checks for !rport->suspended (which, somewhat counter-intuitively, means the PHY is powered on), so add a guard for VBUS as well to avoid a disconnection when a cable is connected.
Fixes: 98898f3bc83c ("phy: rockchip-inno-usb2: support otg-port for rk3399") Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/lkml/20250414185458.7767aabc@booty/ Signed-off-by: Louis Chauvet louis.chauvet@bootlin.com Co-developed-by: Luca Ceresoli luca.ceresoli@bootlin.com Signed-off-by: Luca Ceresoli luca.ceresoli@bootlin.com Reviewed-by: Théo Lebrun theo.lebrun@bootlin.com --- drivers/phy/rockchip/phy-rockchip-inno-usb2.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c index b0f23690ec30..0106d7b7ae24 100644 --- a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c +++ b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c @@ -821,14 +821,16 @@ static void rockchip_chg_detect_work(struct work_struct *work) container_of(work, struct rockchip_usb2phy_port, chg_work.work); struct rockchip_usb2phy *rphy = dev_get_drvdata(rport->phy->dev.parent); struct regmap *base = get_reg_base(rphy); - bool is_dcd, tmout, vout; + bool is_dcd, tmout, vout, vbus_attach; unsigned long delay;
+ vbus_attach = property_enabled(rphy->grf, &rport->port_cfg->utmi_bvalid); + dev_dbg(&rport->phy->dev, "chg detection work state = %d\n", rphy->chg_state); switch (rphy->chg_state) { case USB_CHG_STATE_UNDEFINED: - if (!rport->suspended) + if (!rport->suspended && !vbus_attach) rockchip_usb2phy_power_off(rport->phy); /* put the controller in non-driving mode */ property_enable(base, &rphy->phy_cfg->chg_det.opmode, false);
When the OTG USB port is used to power to SoC, configured as peripheral and used in gadget mode, communication stops without notice about 6 seconds after the gadget is configured and enumerated.
The problem was observed on a Radxa Rock Pi S board, which can only be powered by the only USB-C connector. That connector is the only one usable in gadget mode. This implies the USB cable is connected from before boot and never disconnects while the kernel runs.
The related code flow in the PHY driver code can be summarized as:
* the first time chg_detect_work starts (6 seconds after gadget is configured and enumerated) -> rockchip_chg_detect_work(): if chg_state is UNDEFINED: property_enable(base, &rphy->phy_cfg->chg_det.opmode, false); [Y]
* rockchip_chg_detect_work() changes state and re-triggers itself a few times until it reaches the DETECTED state: -> rockchip_chg_detect_work(): if chg_state is DETECTED: property_enable(base, &rphy->phy_cfg->chg_det.opmode, true); [Z]
At [Y] all existing communications stop. E.g. using a CDC serial gadget, the /dev/tty* devices are still present on both host and device, but no data is transferred anymore. The later call with a 'true' argument at [Z] does not restore it.
Due to the lack of documentation, what chg_det.opmode does exactly is not clear, however by code inspection it seems reasonable that is disables something needed to keep the communication working, and testing proves that disabling these lines lets gadget mode keep working. So prevent changes to chg_det.opmode when there is a cable connected (VBUS present).
Fixes: 98898f3bc83c ("phy: rockchip-inno-usb2: support otg-port for rk3399") Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/lkml/20250414185458.7767aabc@booty/ Signed-off-by: Luca Ceresoli luca.ceresoli@bootlin.com Reviewed-by: Théo Lebrun theo.lebrun@bootlin.com --- drivers/phy/rockchip/phy-rockchip-inno-usb2.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c index 0106d7b7ae24..e5efae7b0135 100644 --- a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c +++ b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c @@ -833,7 +833,8 @@ static void rockchip_chg_detect_work(struct work_struct *work) if (!rport->suspended && !vbus_attach) rockchip_usb2phy_power_off(rport->phy); /* put the controller in non-driving mode */ - property_enable(base, &rphy->phy_cfg->chg_det.opmode, false); + if (!vbus_attach) + property_enable(base, &rphy->phy_cfg->chg_det.opmode, false); /* Start DCD processing stage 1 */ rockchip_chg_enable_dcd(rphy, true); rphy->chg_state = USB_CHG_STATE_WAIT_FOR_DCD; @@ -896,7 +897,8 @@ static void rockchip_chg_detect_work(struct work_struct *work) fallthrough; case USB_CHG_STATE_DETECTED: /* put the controller in normal mode */ - property_enable(base, &rphy->phy_cfg->chg_det.opmode, true); + if (!vbus_attach) + property_enable(base, &rphy->phy_cfg->chg_det.opmode, true); rockchip_usb2phy_otg_sm_work(&rport->otg_sm_work.work); dev_dbg(&rport->phy->dev, "charger = %s\n", chg_to_string(rphy->chg_type));
On Thu, 27 Nov 2025 11:26:15 +0100, Luca Ceresoli wrote:
The USB OTG port of the RK3308 exibits a bug when:
- configured as peripheral, and
- used in gadget mode, and
- the USB cable is connected since before booting
The symptom is: about 6 seconds after configuring gadget mode the device is disconnected and then re-enumerated. This happens only once per boot.
[...]
Applied, thanks!
[1/2] phy: rockchip: inno-usb2: fix disconnection in gadget mode commit: 028e8ca7b20fb7324f3e5db34ba8bd366d9d3acc [2/2] phy: rockchip: inno-usb2: fix communication disruption in gadget mode commit: 7d8f725b79e35fa47e42c88716aad8711e1168d8
Best regards,
linux-stable-mirror@lists.linaro.org
-
Luca Ceresoli -
Vinod Koul