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Message-ID: <20260109005110.oe7phmecseyomie5@synopsys.com>
Date: Fri, 9 Jan 2026 00:51:12 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Sven Peter <sven@...nel.org>
CC: Janne Grunau <j@...nau.net>, Neal Gompa <neal@...pa.dev>,
Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"asahi@...ts.linux.dev" <asahi@...ts.linux.dev>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
James Calligeros <jcalligeros99@...il.com>,
"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: apple: Set USB2 PHY mode before dwc3 init
On Thu, Jan 08, 2026, Sven Peter wrote:
> Now that the upstream code has been getting broader test coverage by our
> users we occasionally see issues with USB2 devices plugged in during boot.
> Before Linux is running, the USB2 PHY has usually been running in device
> mode and it turns out that sometimes host->device or device->host
> transitions don't work.
> The root cause: If the role inside the USB2 PHY is re-configured when it
> has already been powered on or when dwc2 has already enabled the ULPI
> interface the new configuration sometimes doesn't take affect until dwc3
> is reset again. Fix this rare issue by configuring the role much earlier.
> Note that the USB3 PHY does not suffer from this issue and actually
> requires dwc3 to be up before the correct role can be configured there.
>
> Reported-by: James Calligeros <jcalligeros99@...il.com>
> Reported-by: Janne Grunau <j@...nau.net>
> Fixes: 0ec946d32ef7 ("usb: dwc3: Add Apple Silicon DWC3 glue layer driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Sven Peter <sven@...nel.org>
> ---
> drivers/usb/dwc3/dwc3-apple.c | 48 +++++++++++++++++++++++++++++--------------
> 1 file changed, 33 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/usb/dwc3/dwc3-apple.c b/drivers/usb/dwc3/dwc3-apple.c
> index cc47cad232e397ac4498b09165dfdb5bd215ded7..c2ae8eb21d514e5e493d2927bc12908c308dfe19 100644
> --- a/drivers/usb/dwc3/dwc3-apple.c
> +++ b/drivers/usb/dwc3/dwc3-apple.c
> @@ -218,25 +218,31 @@ static int dwc3_apple_core_init(struct dwc3_apple *appledwc)
> return ret;
> }
>
> -static void dwc3_apple_phy_set_mode(struct dwc3_apple *appledwc, enum phy_mode mode)
> -{
> - lockdep_assert_held(&appledwc->lock);
> -
> - /*
> - * This platform requires SUSPHY to be enabled here already in order to properly configure
> - * the PHY and switch dwc3's PIPE interface to USB3 PHY.
> - */
> - dwc3_enable_susphy(&appledwc->dwc, true);
> - phy_set_mode(appledwc->dwc.usb2_generic_phy[0], mode);
> - phy_set_mode(appledwc->dwc.usb3_generic_phy[0], mode);
> -}
> -
> static int dwc3_apple_init(struct dwc3_apple *appledwc, enum dwc3_apple_state state)
> {
> int ret, ret_reset;
>
> lockdep_assert_held(&appledwc->lock);
>
> + /*
> + * The USB2 PHY on this platform must be configured for host or device mode while it is
> + * still powered off and before dwc3 tries to access it. Otherwise, the new configuration
> + * will sometimes only take affect after the *next* time dwc3 is brought up which causes
> + * the connected device to just not work.
> + * The USB3 PHY must be configured later after dwc3 has already been initialized.
> + */
> + switch (state) {
> + case DWC3_APPLE_HOST:
> + phy_set_mode(appledwc->dwc.usb2_generic_phy[0], PHY_MODE_USB_HOST);
> + break;
> + case DWC3_APPLE_DEVICE:
> + phy_set_mode(appledwc->dwc.usb2_generic_phy[0], PHY_MODE_USB_DEVICE);
> + break;
> + default:
> + /* Unreachable unless there's a bug in this driver */
> + return -EINVAL;
> + }
> +
> ret = reset_control_deassert(appledwc->reset);
> if (ret) {
> dev_err(appledwc->dev, "Failed to deassert reset, err=%d\n", ret);
> @@ -257,7 +263,13 @@ static int dwc3_apple_init(struct dwc3_apple *appledwc, enum dwc3_apple_state st
> case DWC3_APPLE_HOST:
> appledwc->dwc.dr_mode = USB_DR_MODE_HOST;
> dwc3_apple_set_ptrcap(appledwc, DWC3_GCTL_PRTCAP_HOST);
> - dwc3_apple_phy_set_mode(appledwc, PHY_MODE_USB_HOST);
> + /*
> + * This platform requires SUSPHY to be enabled here already in order to properly
> + * configure the PHY and switch dwc3's PIPE interface to USB3 PHY. The USB2 PHY
> + * has already been configured to the correct mode earlier.
> + */
> + dwc3_enable_susphy(&appledwc->dwc, true);
> + phy_set_mode(appledwc->dwc.usb3_generic_phy[0], PHY_MODE_USB_HOST);
> ret = dwc3_host_init(&appledwc->dwc);
> if (ret) {
> dev_err(appledwc->dev, "Failed to initialize host, ret=%d\n", ret);
> @@ -268,7 +280,13 @@ static int dwc3_apple_init(struct dwc3_apple *appledwc, enum dwc3_apple_state st
> case DWC3_APPLE_DEVICE:
> appledwc->dwc.dr_mode = USB_DR_MODE_PERIPHERAL;
> dwc3_apple_set_ptrcap(appledwc, DWC3_GCTL_PRTCAP_DEVICE);
> - dwc3_apple_phy_set_mode(appledwc, PHY_MODE_USB_DEVICE);
> + /*
> + * This platform requires SUSPHY to be enabled here already in order to properly
> + * configure the PHY and switch dwc3's PIPE interface to USB3 PHY. The USB2 PHY
> + * has already been configured to the correct mode earlier.
> + */
> + dwc3_enable_susphy(&appledwc->dwc, true);
> + phy_set_mode(appledwc->dwc.usb3_generic_phy[0], PHY_MODE_USB_DEVICE);
> ret = dwc3_gadget_init(&appledwc->dwc);
> if (ret) {
> dev_err(appledwc->dev, "Failed to initialize gadget, ret=%d\n", ret);
>
> ---
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> change-id: 20260108-dwc3-apple-usb2phy-fix-cf1d26018dd0
>
> Best regards,
> --
> Sven Peter <sven@...nel.org>
>
Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Thanks,
Thinh
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