linux-kernel - [PATCH] usb: dwc3: Properly handle processing of pending events

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Message-Id: <20230801192658.19275-1-quic_eserrao@quicinc.com>
Date:   Tue,  1 Aug 2023 12:26:58 -0700
From:   Elson Roy Serrao <quic_eserrao@...cinc.com>
To:     Thinh.Nguyen@...opsys.com, gregkh@...uxfoundation.org,
        felipe.balbi@...ux.intel.com, rogerq@...nel.org,
        surong.pang@...soc.com
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        quic_wcheng@...cinc.com, quic_jackp@...cinc.com,
        Elson Roy Serrao <quic_eserrao@...cinc.com>,
        stable@...r.kernel.org
Subject: [PATCH] usb: dwc3: Properly handle processing of pending events

If dwc3 is runtime suspended we defer processing the event buffer
until resume, by setting the pending_events flag. Set this flag before
triggering resume to avoid race with the runtime resume callback.

While handling the pending events, in addition to checking the event
buffer we also need to process it. Handle this by explicitly calling
dwc3_thread_interrupt(). Also balance the runtime pm get() operation
that triggered this processing.

Cc: stable@...r.kernel.org
Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
---
Change separated from below series as an independent fix based on the
earlier discussion
https://lore.kernel.org/all/be57511d-2005-a1f5-d5a5-809e71029aec@quicinc.com/

 drivers/usb/dwc3/gadget.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 5fd067151fbf..858fe4c299b7 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -4455,9 +4455,14 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
 	u32 count;
 
 	if (pm_runtime_suspended(dwc->dev)) {
+		dwc->pending_events = true;
+		/*
+		 * Trigger runtime resume. The get() function will be balanced
+		 * after processing the pending events in dwc3_process_pending
+		 * events().
+		 */
 		pm_runtime_get(dwc->dev);
 		disable_irq_nosync(dwc->irq_gadget);
-		dwc->pending_events = true;
 		return IRQ_HANDLED;
 	}
 
@@ -4718,6 +4723,8 @@ void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
 {
 	if (dwc->pending_events) {
 		dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
+		dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
+		pm_runtime_put(dwc->dev);
 		dwc->pending_events = false;
 		enable_irq(dwc->irq_gadget);
 	}
-- 
2.17.1