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Date:   Tue, 30 Mar 2021 13:16:48 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc:     Sandeep Maheswaram <sanm@codeaurora.org>,
        Felipe Balbi <balbi@kernel.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Doug Anderson <dianders@chromium.org>,
        Matthias Kaehlcke <mka@chromium.org>,
        linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, Manu Gautam <mgautam@codeaurora.org>
Subject: Re: [PATCH v1] usb: dwc3: core: Add shutdown callback for dwc3
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On Tue, Mar 30, 2021 at 03:25:58PM +0530, Sai Prakash Ranjan wrote:
> On 2021-03-30 14:37, Greg Kroah-Hartman wrote:
> > On Tue, Mar 30, 2021 at 02:12:04PM +0530, Sandeep Maheswaram wrote:
> > > 
> > > On 3/26/2021 7:07 PM, Greg Kroah-Hartman wrote:
> > > > On Wed, Mar 24, 2021 at 12:57:32AM +0530, Sandeep Maheswaram wrote:
> > > > > This patch adds a shutdown callback to USB DWC core driver to ensure that
> > > > > it is properly shutdown in reboot/shutdown path. This is required
> > > > > where SMMU address translation is enabled like on SC7180
> > > > > SoC and few others. If the hardware is still accessing memory after
> > > > > SMMU translation is disabled as part of SMMU shutdown callback in
> > > > > system reboot or shutdown path, then IOVAs(I/O virtual address)
> > > > > which it was using will go on the bus as the physical addresses which
> > > > > might result in unknown crashes (NoC/interconnect errors).
> > > > >
> > > > > Previously this was added in dwc3 qcom glue driver.
> > > > > https://patchwork.kernel.org/project/linux-arm-msm/list/?series=382449
> > > > > But observed kernel panic as glue driver shutdown getting called after
> > > > > iommu shutdown. As we are adding iommu nodes in dwc core node
> > > > > in device tree adding shutdown callback in core driver seems correct.
> > > > So shouldn't you also remove this from the qcom glue driver at the same
> > > > time?  Please submit both as a patch series.
> > > >
> > > > thanks,
> > > >
> > > > greg k-h
> > > 
> > > Hi Greg,
> > > 
> > > The qcom glue driver patch is not merged yet. I have just mentioned
> > > for it for reference.
> > 
> > You know that we can not add callbacks for no in-kernel user, so what
> > good is this patch for now?
> > 
> 
> What in-kernel user? Since when does shutdown callback need an in-kernel
> user? When you reboot or shutdown a system, it gets called. The reason
> why the shutdown callback is needed is provided in the commit text.

As I can't see the patch here, I have no idea...