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

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Date:   Wed, 2 Aug 2023 00:11:47 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Roy Serrao <quic_eserrao@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "rogerq@...nel.org" <rogerq@...nel.org>,
        "surong.pang@...soc.com" <surong.pang@...soc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Properly handle processing of pending events

On Tue, Aug 01, 2023, Elson Roy Serrao wrote:
> 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://urldefense.com/v3/__https://lore.kernel.org/all/be57511d-2005-a1f5-d5a5-809e71029aec@quicinc.com/__;!!A4F2R9G_pg!YtZ93ALEpDNTCEhf0WEyB5S090pPlKIKVtjqTOAEJdxdWbl8QG6eiRmlvfivUtD5qjKWWLX2C4fb4W8VAg5w9qasLuKB$ 
> 
>  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
> 

This fix is more complete.

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh