linux-kernel - [PATCH] usb: dwc2: drd: fix clock gating on USB role switch

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Message-Id: <20240903094156.6516-1-tomas.marek@elrest.cz>
Date: Tue,  3 Sep 2024 11:41:56 +0200
From: Tomas Marek <tomas.marek@...est.cz>
To: hminas@...opsys.com,
	gregkh@...uxfoundation.org
Cc: Arthur.Petrosyan@...opsys.com,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	oleg.karfich@...o.com
Subject: [PATCH] usb: dwc2: drd: fix clock gating on USB role switch

The dwc2_handle_usb_suspend_intr() function disables gadget clocks in USB
peripheral mode when no other power-down mode is available (introduced by
commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")).
However, the dwc2_drd_role_sw_set() USB role update handler attempts to
read DWC2 registers if the USB role has changed while the USB is in suspend
mode (when the clocks are gated). This causes the system to hang.

Release gadget clocks before handling the USB role update.

Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")

Signed-off-by: Tomas Marek <tomas.marek@...est.cz>
---
 drivers/usb/dwc2/drd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
index a8605b02115b..ccb33cd1f04b 100644
--- a/drivers/usb/dwc2/drd.c
+++ b/drivers/usb/dwc2/drd.c
@@ -127,6 +127,18 @@ static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
 			role = USB_ROLE_DEVICE;
 	}
 
+#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
+	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
+	if (dwc2_is_device_mode(hsotg)) {
+		if (hsotg->lx_state == DWC2_L2) {
+			if (hsotg->params.power_down ==
+			    DWC2_POWER_DOWN_PARAM_NONE && hsotg->bus_suspended &&
+			    !hsotg->params.no_clock_gating)
+				dwc2_gadget_exit_clock_gating(hsotg, 0);
+		}
+	}
+#endif
+
 	if (role == USB_ROLE_HOST) {
 		already = dwc2_ovr_avalid(hsotg, true);
 	} else if (role == USB_ROLE_DEVICE) {
-- 
2.25.1