linux-kernel - [PATCH] usb: dwc2: fix resume failure if dr

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Message-ID: <20260129021534.10411-1-jszhang@kernel.org>
Date: Thu, 29 Jan 2026 10:15:34 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Minas Harutyunyan <hminas@...opsys.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] usb: dwc2: fix resume failure if dr_mode is host

commit 13b1f8e25bfd1 ("usb: dwc2: Force mode optimizations") removed the
dwc2_force_mode(hsotg, true) in dwc2_force_dr_mode() if dr_mode is host.

But this brings a bug: the controller fails to resume back as host,
further debugging shows that the controller is resumed as peripheral.
The reason is dwc2_force_dr_mode() missed the host mode forcing, and
when resuming from s2ram, GINTSTS is 0 by default, dwc2_is_device_mode
in dwc2_resume() misreads this as the controller is in peripheral mode.

Fix the resume failure by adding back the dwc2_force_mode(hsotg, true).

Then an obvious question is: why this bug hasn't been observed and fixed
for about six years? There are two resons: most dwc2 platforms set the
dr_mode as otg; Some platforms don't have suspend & resume support yet.

Fixes: 13b1f8e25bfd1 ("usb: dwc2: Force mode optimizations")
Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
---
 drivers/usb/dwc2/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c
index c3d24312db0f..f375c5185bfe 100644
--- a/drivers/usb/dwc2/core.c
+++ b/drivers/usb/dwc2/core.c
@@ -578,6 +578,7 @@ void dwc2_force_dr_mode(struct dwc2_hsotg *hsotg)
 {
 	switch (hsotg->dr_mode) {
 	case USB_DR_MODE_HOST:
+		dwc2_force_mode(hsotg, true);
 		/*
 		 * NOTE: This is required for some rockchip soc based
 		 * platforms on their host-only dwc2.
-- 
2.51.0