linux-kernel - Re: [PATCH] usb: dwc3: qcom: Add shutdown handler

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Message-ID: <6159dcff-f6cf-416f-9573-d8753ed58a6c@oss.qualcomm.com>
Date: Mon, 28 Jul 2025 10:51:59 +0530
From: Prashanth K <prashanth.k@....qualcomm.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
        Krishna Kurapati <krishna.kurapati@....qualcomm.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: qcom: Add shutdown handler



On 7/25/2025 5:29 PM, Greg Kroah-Hartman wrote:
> On Fri, Jul 25, 2025 at 03:28:12PM +0530, Prashanth K wrote:
>>
>>
>> On 7/25/2025 2:18 PM, Greg Kroah-Hartman wrote:
>>> On Fri, Jul 25, 2025 at 11:51:58AM +0530, Prashanth K wrote:
>>>> Currently during system reboot, SMMU disables its translations
>>>> while devices like USB may still be actively using DMA buffers.
>>>> This can lead to NOC errors and system crashes due to invalid
>>>> memory access.
>>>>
>>>> Address this by adding a shutdown callback to dwc3-qcom, which
>>>> ensures proper teardown of UDC stack and prevents DWC3 controller
>>>> from accessing memory after SMMU translation is disabled. Reuse
>>>> the existing remove callback for this purpose.
>>>>
>>>> Signed-off-by: Prashanth K <prashanth.k@....qualcomm.com>
>>>> ---
>>>>  drivers/usb/dwc3/dwc3-qcom.c | 8 ++++++--
>>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> What commit id does this fix?  Or is this just a new feature?
>>>
>>> thanks,
>>>
>>> greg k-h
>>
>> I didn't Fixes tag because a small dilemma. This patch is rebased on top
>> of the flattening series, specifically commit 1881a32fe14d ("usb: dwc3:
>> qcom: Transition to flattened model").
>> However, I don't think that this commit caused this issue.
>>
>> Let me know if you want the Fixes tag.
> 
> If you don't need/want this backported to any stable tree, then leave it
> as-is.  Your choice.
> 

Lets not take it to stable now, because it will cause conflicts.
If we encounter any issue in future, we can manually resolve the
conflict and backport to stable.

Regards,
Prashanth K