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

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Message-ID: <c984ff015109ed606d2933125d385015@codeaurora.org>
Date:   Tue, 30 Mar 2021 18:18:43 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sandeep Maheswaram <sanm@...eaurora.org>,
        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 2021-03-30 16:46, Greg Kroah-Hartman wrote:
> 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...

You are replying now to the same patch which adds this shutdown callback 
:)
Anyways the qcom dwc3 driver patch which is abandoned which is also 
mentioned
in the commit text is here [1] and the new shutdown callback patch which 
we
are both replying to is in here [2]

[1] 
https://lore.kernel.org/lkml/1605162619-10064-1-git-send-email-sanm@codeaurora.org/

[2] 
https://lore.kernel.org/lkml/1616527652-7937-1-git-send-email-sanm@codeaurora.org/

Thanks,
Sai

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