linux-kernel - Re: [PATCH v1] usb: dwc3: core: Add shutdown callback for dwc3

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Date:   Tue, 30 Mar 2021 11:07:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sandeep Maheswaram <sanm@...eaurora.org>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Manu Gautam <mgautam@...eaurora.org>
Subject: Re: [PATCH v1] usb: dwc3: core: Add shutdown callback for dwc3

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?

confused,

greg k-h