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

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Message-ID: <2025072512-hertz-dentist-67dc@gregkh>
Date: Fri, 25 Jul 2025 13:59:39 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Prashanth K <prashanth.k@....qualcomm.com>
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 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.