linux-kernel - [PATCH v2] usb: dwc2: drd: fix clock gating on USB role switch

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Message-Id: <20240906055025.25057-1-tomas.marek@elrest.cz>
Date: Fri,  6 Sep 2024 07:50:25 +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,
	stable@...r.kernel.org
Subject: [PATCH v2] 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 the gadget clocks before handling the USB role update.

Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")
Cc: stable@...r.kernel.org
Signed-off-by: Tomas Marek <tomas.marek@...est.cz>
---
Changes in v2:
 - CC stable@...r.kernel.org
 - merge ifdef and nested if statements into one if statement
---
 drivers/usb/dwc2/drd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
index a8605b02115b..1ad8fa3f862a 100644
--- a/drivers/usb/dwc2/drd.c
+++ b/drivers/usb/dwc2/drd.c
@@ -127,6 +127,15 @@ 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)) &&
+	     dwc2_is_device_mode(hsotg) &&
+	     hsotg->lx_state == DWC2_L2 &&
+	     hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_NONE &&
+	     hsotg->bus_suspended &&
+	     !hsotg->params.no_clock_gating)
+		dwc2_gadget_exit_clock_gating(hsotg, 0);
+
 	if (role == USB_ROLE_HOST) {
 		already = dwc2_ovr_avalid(hsotg, true);
 	} else if (role == USB_ROLE_DEVICE) {
-- 
2.25.1