Do not re-init OTG host registers on a live controller

dwc3_otg_host_init() carries the comment "should be called before Host controller driver is started". It rewrites OCTL/OCFG, touches GUSB2PHYCFG and re-asserts port power (OCTL.PrtPwrCtl). dwc3_otg_irq() sets otg_restart_host ONLY when current_otg_role is already DWC3_OTG_ROLE_HOST. The threaded handler then calls dwc3_otg_host_init() unconditionally, so that path always ran against a live, running host -- the exact condition the comment forbids. Re-asserting port power under a running xHCI corrupts an in-flight command. Observed on the RV1106 86-panel as the controller failing to answer a Stop Endpoint command, after which xhci-hcd declares it dead and tears the bus down. An r8152 USB NIC stalls a transfer and the controller died 8 times out of 8 between 452s and 587s. Compiling the OTG path out entirely (dr_mode=host) survived 1810s with zero deaths, which localised it here. On this board the event is always spurious: the dwc3 node deliberately carries no extcon, because wiring it pins the role to peripheral on D1-modded panels, and CONIDSTS reads 0 -- so the role cannot legitimately change while host is current. Skip the re-init in that case and log it at debug level. This does not remove the restart capability. dwc3_set_mode() still runs immediately below, and if the role has genuinely changed dwc3_otg_update() performs a proper dwc3_host_exit() before re-initialising. The only behaviour removed is poking a running controller, which was never legitimate. Refs flare-edge#160 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MVGTC78dgCGfRANNKjoPea
2026-09-22 16:54:54 -06:00
parent e12bb2c554
commit 9ff60d60db
1 changed files with 40 additions and 0 deletions
@@ -0,0 +1,40 @@
 diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
 --- a/drivers/usb/dwc3/drd.c
 +++ b/drivers/usb/dwc3/drd.c
@@ -55,7 +55,35 @@
 	spin_lock(&dwc->lock);
 	if (dwc->otg_restart_host) {
 -		dwc3_otg_host_init(dwc);
 +		/*
 +		 * dwc3_otg_host_init() is documented just above its definition as
 +		 * "should be called before Host controller driver is started": it
 +		 * rewrites OCTL/OCFG, touches GUSB2PHYCFG and re-asserts port power
 +		 * (OCTL.PrtPwrCtl). Doing that to a controller that is already
 +		 * running corrupts an in-flight command.
 +		 *
 +		 * But otg_restart_host is set in dwc3_otg_irq() ONLY when
 +		 * current_otg_role is already DWC3_OTG_ROLE_HOST, so this path
 +		 * always ran it against a live host -- the exact condition the
 +		 * comment forbids. Observed on the RV1106 86-panel as the xHCI
 +		 * controller failing to answer a Stop Endpoint command, after which
 +		 * xhci-hcd declares it dead and tears the bus down: an r8152 NIC
 +		 * would stall a transfer and the controller died 8 times out of 8
 +		 * between 452s and 587s. (flare-edge#160)
 +		 *
 +		 * On this board the event is always spurious: the dwc3 node
 +		 * deliberately carries no extcon (wiring it pins the role to
 +		 * peripheral on D1-modded panels) and CONIDSTS reads 0, so the role
 +		 * cannot legitimately change while host is current. Skip the
 +		 * re-init in that case. dwc3_set_mode() below still re-evaluates
 +		 * the role, and if it has genuinely changed dwc3_otg_update() does
 +		 * a proper dwc3_host_exit() before re-initialising.
 +		 */
 +		if (dwc->current_otg_role == DWC3_OTG_ROLE_HOST)
 +			dev_dbg(dwc->dev,
 +				"OTG event while host is live; skipping host re-init\n");
 +		else
 +			dwc3_otg_host_init(dwc);
 		dwc->otg_restart_host = false;
 	}