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

Sai Prakash Ranjan
2021-03-30T09:56:47Z

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.

Confused,
Sai Prakash Ranjan

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