[PATCH v2] usb: dwc3: tell xHCI that it lost its state when the core is powered off

[Joonhoe Kim <26rote@gmail.com>]

dwc3_suspend_common() powers the core off for system suspend
(dwc3_core_exit()) in OTG mode (DWC3_GCTL_PRTCAP_OTG), and in host mode
when the controller may not wake the system or needs a full re-init. The
xHCI registers and the state saved with the Controller Save State
command are gone then, but nothing tells xhci-plat: xhci_resume() takes
the "state intact" path, writes the saved registers back and asks the
controller to restore its state (CRS).

xhci-plat has a flag for exactly this, power_lost (commit 668cc6bc1178
("usb: host: xhci-plat: allow upper layers to signal power loss"), used
by cdns3), but dwc3 never sets it.

On a Lenovo Y700 Gen 5 (TB323FU, SM8850; DWC3 + eUSB2 PHY) with a USB
2.0 hub, a USB 3 flash drive and a Billboard device attached, and USB
wakeup disabled, s2idle then broke the host controller on resume: either
the controller wrote to an address that was not mapped

  arm-smmu 15000000.iommu: Unhandled context fault: fsr=0x402,
    iova=0xd85e7c300, fsynr=0x3d0011, cbfrsynra=0x40, cb=13
  xhci-hcd xhci-hcd.2.auto: WARNING: Host System Error
  usb 1-1: hub failed to enable device, error -108

or its command ring would not stop

  xhci-hcd xhci-hcd.2.auto: Abort failed to stop command ring: -110
  xhci-hcd xhci-hcd.2.auto: xHCI host controller not responding, assume dead
  xhci-hcd xhci-hcd.2.auto: HC died; cleaning up
  usb 1-1: PM: **** DPM device timeout ****
  Kernel panic - not syncing: usb 1-1: unrecoverable failure

With wakeup enabled (the core stays powered) the same setup survived
every cycle.

Record that the core was powered off and pass this to xhci-plat as
power_lost from a resume_quirk, so that xhci_resume() resets the
controller and the devices are re-enumerated. Unlike a static
XHCI_RESET_ON_RESUME this only applies to the resumes that follow a
power-off; resumes with the core kept powered (host mode with wakeup
enabled) and runtime resume keep the restore path. Clear the flag once
xhci-plat has read it, so that a later system suspend that fails before
the dwc3 core is suspended does not reset the controller.

Fixes: c4a5153e87fd ("usb: dwc3: core: Power-off core/PHYs on system_suspend in host mode")
Fixes: f09cc79b4b33 ("usb: dwc3: add dual role support using OTG block")
Signed-off-by: Joonhoe Kim <26rote@gmail.com>
---
v2:
- Also set the flag when the core is powered off in OTG mode with the
  host role active (Sashiko [1])
- Clear the flag once xhci-plat has read it (Sashiko [1]), instead of in
  the host branch that keeps the core powered
- Drop the comment above the resume quirk
- Add a Fixes tag for the OTG branch
- Rebased on next-20261111

Testing, 30 s RTC s2idle with wakeup disabled on the setup above:
without this change 1/1 cycles lost the controller; with this version
3/3 cycles reset the controller and re-enumerated all devices.
OTG mode (DWC3_GCTL_PRTCAP_OTG) is not tested; this board switches
roles through usb-role-switch and never uses it.

host.c now includes xhci.h for hcd_to_xhci_priv().

v1: https://lore.kernel.org/all/20260929130252.869-1-26rote@gmail.com/
RESEND: https://lore.kernel.org/all/20261112114053.412-1-26rote@gmail.com/
[1] https://lore.kernel.org/all/sashiko-outbox-211064@kernel.org/

 drivers/usb/dwc3/core.c |  3 +++
 drivers/usb/dwc3/core.h |  3 +++
 drivers/usb/dwc3/host.c | 15 ++++++++++++---
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 372737f47..1ddd860e1 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -2572,6 +2572,7 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
 		if (!PMSG_IS_AUTO(msg) &&
 		    (!device_may_wakeup(dwc->dev) || dwc->needs_full_reinit)) {
 			dwc3_core_exit(dwc);
+			dwc->xhci_power_lost = 1;
 			break;
 		}
 
@@ -2608,6 +2609,8 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
 
 		dwc3_otg_exit(dwc);
 		dwc3_core_exit(dwc);
+		if (dwc->current_otg_role == DWC3_OTG_ROLE_HOST)
+			dwc->xhci_power_lost = 1;
 		break;
 	default:
 		/* do nothing */
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 267c922ca..4bc94bb07 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1185,6 +1185,8 @@ struct dwc3_glue_ops {
  * @suspended: set to track suspend event due to U3/L2.
  * @susphy_state: state of DWC3_GUSB2PHYCFG_SUSPHY + DWC3_GUSB3PIPECTL_SUSPHY
  *		  before PM suspend.
+ * @xhci_power_lost: the core was powered off for system suspend; xHCI
+ *		     must not try to restore its state on resume
  * @imod_interval: set the interrupt moderation interval in 250ns
  *			increments or 0 to disable.
  * @max_cfg_eps: current max number of IN eps used across all USB configs.
@@ -1440,6 +1442,7 @@ struct dwc3 {
 	unsigned		wakeup_configured:1;
 	unsigned		suspended:1;
 	unsigned		susphy_state:1;
+	unsigned		xhci_power_lost:1;
 
 	u16			imod_interval;
 
diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
index c5674161b..0cb6e64d1 100644
--- a/drivers/usb/dwc3/host.c
+++ b/drivers/usb/dwc3/host.c
@@ -14,9 +14,7 @@
 #include <linux/usb/hcd.h>
 #include <linux/bitfield.h>
 
-#include "../host/xhci-port.h"
-#include "../host/xhci-ext-caps.h"
-#include "../host/xhci-caps.h"
+#include "../host/xhci.h"
 #include "../host/xhci-plat.h"
 #include "core.h"
 
@@ -78,7 +76,18 @@ static void dwc3_xhci_plat_start(struct usb_hcd *hcd)
 	dwc3_enable_susphy(dwc, true);
 }
 
+static int dwc3_xhci_resume_quirk(struct usb_hcd *hcd)
+{
+	struct dwc3 *dwc = dev_get_drvdata(hcd->self.controller->parent);
+
+	hcd_to_xhci_priv(hcd)->power_lost = dwc->xhci_power_lost;
+	dwc->xhci_power_lost = 0;
+
+	return 0;
+}
+
 static const struct xhci_plat_priv dwc3_xhci_plat_quirk = {
+	.resume_quirk = dwc3_xhci_resume_quirk,
 	.plat_start = dwc3_xhci_plat_start,
 };
 

base-commit: aaa2f954c21b205a0bcd0961e5b2be4e82e58455
-- 
2.53.0