linux-kernel - Re: [PATCH] usb: dwc3: Remove WARN_ON for device endpoint command timeouts

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Message-ID: <20250807005638.thhsgjn73aaov2af@synopsys.com>
Date: Thu, 7 Aug 2025 00:56:39 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Selvarasu Ganesan <selvarasu.g@...sung.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "m.grzeschik@...gutronix.de" <m.grzeschik@...gutronix.de>,
        "balbi@...com" <balbi@...com>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jh0801.jung@...sung.com" <jh0801.jung@...sung.com>,
        "dh10.jung@...sung.com" <dh10.jung@...sung.com>,
        "akash.m5@...sung.com" <akash.m5@...sung.com>,
        "hongpooh.kim@...sung.com" <hongpooh.kim@...sung.com>,
        "eomji.oh@...sung.com" <eomji.oh@...sung.com>,
        "shijie.cai@...sung.com" <shijie.cai@...sung.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "muhammed.ali@...sung.com" <muhammed.ali@...sung.com>,
        "thiagu.r@...sung.com" <thiagu.r@...sung.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Remove WARN_ON for device endpoint command
 timeouts

On Wed, Aug 06, 2025, Selvarasu Ganesan wrote:
> 
> On 8/6/2025 5:08 AM, Thinh Nguyen wrote:
> > On Mon, Aug 04, 2025, Selvarasu Ganesan wrote:
> >> From: Akash M <akash.m5@...sung.com>
> >>
> >> This commit addresses a rarely observed endpoint command timeout
> >> which causes kernel panic due to warn when 'panic_on_warn' is enabled
> >> and unnecessary call trace prints when 'panic_on_warn' is disabled.
> >> It is seen during fast software-controlled connect/disconnect testcases.
> >> The following is one such endpoint command timeout that we observed:
> >>
> >> 1. Connect
> >>     =======
> >> ->dwc3_thread_interrupt
> >>   ->dwc3_ep0_interrupt
> >>    ->configfs_composite_setup
> >>     ->composite_setup
> >>      ->usb_ep_queue
> >>       ->dwc3_gadget_ep0_queue
> >>        ->__dwc3_gadget_ep0_queue
> >>         ->__dwc3_ep0_do_control_data
> >>          ->dwc3_send_gadget_ep_cmd
> >>
> >> 2. Disconnect
> >>     ==========
> >> ->dwc3_thread_interrupt
> >>   ->dwc3_gadget_disconnect_interrupt
> >>    ->dwc3_ep0_reset_state
> >>     ->dwc3_ep0_end_control_data
> >>      ->dwc3_send_gadget_ep_cmd
> >>
> >> In the issue scenario, in Exynos platforms, we observed that control
> >> transfers for the previous connect have not yet been completed and end
> >> transfer command sent as a part of the disconnect sequence and
> >> processing of USB_ENDPOINT_HALT feature request from the host timeout.
> >> This maybe an expected scenario since the controller is processing EP
> >> commands sent as a part of the previous connect. It maybe better to
> >> remove WARN_ON in all places where device endpoint commands are sent to
> >> avoid unnecessary kernel panic due to warn.
> >>
> >> Fixes: e192cc7b5239 ("usb: dwc3: gadget: move cmd_endtransfer to extra function")
> >> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> >> Fixes: c7fcdeb2627c ("usb: dwc3: ep0: simplify EP0 state machine")
> >> Fixes: f0f2b2a2db85 ("usb: dwc3: ep0: push ep0state into xfernotready processing")
> >> Fixes: 2e3db064855a ("usb: dwc3: ep0: drop XferNotReady(DATA) support")
> >> Cc: stable@...r.kernel.org
> > I don't think this is a fix patch. You're just replacing WARN* with
> > dev_warn* without doing any recovery. Let's remove the Fixes and table
> > tag. Also, can we replace dev_warn* with dev_err* because these are
> > critical errors that may put the controller in a bad state.
> >
> > Thanks,
> > Thinh
> 
> 
> Hi Thinh,
> 
> Thanks for your review comments.
> Yeah we agree. This is not a fix patch. Sure we will update new patchset 
> with replace dev_warn* with dev_err*.
> 
> As for dropping the stable tag,  It would be better these changes to be 
> applied across all stable kernels, so shall we keep stable tag in place?
> 

That's fine with me.

BR,
Thinh