linux-kernel - Re: [PATCH v9 5/5] iommu/arm-smmu: Add support for qcom,smmu-v2 variant

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Date:   Wed, 28 Mar 2018 14:11:07 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
CC:     <joro@...tes.org>, <robin.murphy@....com>,
        <iommu@...ts.linux-foundation.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <mark.rutland@....com>,
        <linux-arm-msm@...r.kernel.org>, Will Deacon <will.deacon@....com>,
        Gaojianbo <gaojianbo@...ilicon.com>
Subject: Re: [PATCH v9 5/5] iommu/arm-smmu: Add support for qcom,smmu-v2
 variant

Hi Vivek,

On 2018/3/28 12:37, Vivek Gautam wrote:
> Hi Yisheng
> 
> 
> On 3/28/2018 6:54 AM, Yisheng Xie wrote:
>> Hi Vivek,
>>
>> On 2018/3/13 16:55, Vivek Gautam wrote:
>>> +- power-domains:  Specifiers for power domains required to be powered on for
>>> +                  the SMMU to operate, as per generic power domain bindings.
>>> +
>> In this patchset, power-domains is not used right? And you just do the clock gating,
>> but not power gating, right?
> 
> We are handling the power-domains too. Please see the example in this binding doc.

I see, but I do not find the point in code of these patchset, do you mean PMIC(e.g mmcc)
will gate the power domain of SMMU(e.g. MDSS_GDSC of mmcc) when PMIC suspend?

> 
>>
>> Another question is if smmu do power gating, it will reset some of its registers, so
>> it need save at suspend and restore at resume, right?
> 
> Qualcomm implementation of the arm-smmu has the retenetion enabled. So the smmu doesn't
> loose state when power is pulled out of it.
> And now we are just selectively enabling the runtime pm. So only the platforms that can really
> support runtime pm can enable it.

Get it, thanks for your explain.

Thanks
Yisheng
> 
> Thanks
> Vivek
>>
>> Thanks
>> Yisheng
>>
> 
> 
>