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SubjectRe: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF
Hi Robin,

On 2020-06-03 19:10, Robin Murphy wrote:
> On 2020-06-03 13:26, Sai Prakash Ranjan wrote:
>> Hi Robin,
>>
>> On 2020-06-03 17:51, Robin Murphy wrote:
>>> On 2020-06-03 13:00, Sai Prakash Ranjan wrote:
>>>> Hi Robin, Mathieu
>>>>
>>>> On 2020-06-03 17:07, Robin Murphy wrote:
>>>>> On 2020-06-01 22:28, Mathieu Poirier wrote:
>>>>>> That being said I'm sure that dependencies on an IOMMU isn't a
>>>>>> problem confined
>>>>>> to coresight. I am adding Robin Murphy, who added this commit [1],
>>>>>> to the thread
>>>>>> in the hope that he can provide guidance on the right way to do
>>>>>> this.
>>>>>
>>>>> Right, it's not specific to CoreSight, and it's not even specific
>>>>> to
>>>>> IOMMUs really. In short, blame kexec ;)
>>>>>
>>>>
>>>> Yes it is not specific to coresight, we are targeting this for all
>>>> consumers/clients of SMMU(atleast on SC7180 SoC). We have display
>>>> throwing
>>>> NoC/interconnect errors[1] during reboot after SMMU is disabled.
>>>> This is also not specific to kexec either as you explained here [2]
>>>> about
>>>> a case with display which is exacly what is happening in our system
>>>> [1].
>>>
>>> Sure, but those instances are begging the question of why the SMMU is
>>> disabled at reboot in the first place ;)
>>>
>>
>> That is what happens in SMMU shutdown callback right? It is the
>> reboot/shutdown flow.
>
> Yes, that's where it happens, but my point is *why* it happens at all.
>
> hint: `git log --grep=shutdown drivers/iommu/`
>

Ah my change :)

> If we could assume the system is always about to be powered off or
> reset, we wouldn't need to do anything to the SMMU either ;)
>

Are you hinting at removing SMMU shutdown callback altogether ;)

Thanks,
Sai

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