Re: [PATCH] iommu/arm-smmu: Demote error messages to debug in shutdown callback

Sai Prakash Ranjan
2020-03-27T18:18:45Z

Hi Rob,

On 2020-03-27 21:47, Rob Clark wrote:
> On Fri, Mar 27, 2020 at 8:10 AM Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
>>
>> Hi Robin,
>>
>> Thanks for taking a look at this.
>>
>> On 2020-03-27 19:42, Robin Murphy wrote:
>> > On 2020-03-27 1:28 pm, Sai Prakash Ranjan wrote:
>> >> Currently on reboot/shutdown, the following messages are
>> >> displayed on the console as error messages before the
>> >> system reboots/shutdown.
>> >>
>> >> On SC7180:
>> >>
>> >> arm-smmu 15000000.iommu: removing device with active domains!
>> >> arm-smmu 5040000.iommu: removing device with active domains!
>> >>
>> >> Demote the log level to debug since it does not offer much
>> >> help in identifying/fixing any issue as the system is anyways
>> >> going down and reduce spamming the kernel log.
>> >
>> > I've gone back and forth on this pretty much ever since we added the
>> > shutdown hook - on the other hand, if any devices *are* still running
>> > in those domains at this point, then once we turn off the SMMU and let
>> > those IOVAs go out on the bus as physical addresses, all manner of
>> > weirdness may ensue. Thus there is an argument for *some* indication
>> > that this may happen, although IMO it could be downgraded to at least
>> > dev_warn().
>> >
>>
>> Any pointers to the weirdness here after SMMU is turned off?
>> Because if we look at the call sites, device_shutdown is called
>> from kernel_restart_prepare or kernel_shutdown_prepare which would
>> mean system is going down anyways, so do we really care about these
>> error messages or warnings from SMMU?
>>
>> arm_smmu_device_shutdown
>> platform_drv_shutdown
>> device_shutdown
>> kernel_restart_prepare
>> kernel_restart
>>
>
> I'd guess that drm/msm is not detaching all of it's UNMANAGED domains
> in shutdown. Although *presumably* the device_link stuff would
> prevent the SMMU from shutting down while gpu/display is still active?
> If not I think we have bigger problems.
>

Where is the shutdown callback in drm/msm? I don't see any...

Thanks,
Sai

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