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Subject: Re: [PATCH v4 08/13] iommu/rockchip: Control clocks needed to access
 the IOMMU
To:     JeffyChen <jeffy.chen@rock-chips.com>, tfiga@chromium.org
Cc:     Robin Murphy <robin.murphy@arm.com>, linux-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        devicetree@vger.kernel.org, xxm@rock-chips.com,
        Joerg Roedel <joro@8bytes.org>, jcliang@chromium.org,
        linux-rockchip@lists.infradead.org,
        iommu@lists.linux-foundation.org, Rob Herring <robh+dt@kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        Heiko Stuebner <heiko@sntech.de>
References: <20180118115251.5542-1-jeffy.chen@rock-chips.com>
 <20180118115251.5542-9-jeffy.chen@rock-chips.com>
 <c188e6a9-744c-d984-545c-408607f35cc9@arm.com>
 <5A60AE41.2050101@rock-chips.com>
 <1f4b3c0d-1414-0012-a072-f4a11f432c21@rock-chips.com>
 <5A654925.9020203@rock-chips.com> <5A6563FA.8080602@rock-chips.com>
From:   Randy Li <randy.li@rock-chips.com>
Organization: Fuzhou Rockchip
Message-ID: <c05d4794-b76d-cfaa-d7ed-c44108117ee2@rock-chips.com>
Date:   Thu, 25 Jan 2018 17:42:17 +0800
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On 01/22/2018 12:09 PM, JeffyChen wrote:
> Hi Randy,
> 
> On 01/22/2018 10:15 AM, JeffyChen wrote:
>> Hi Randy,
>>
>> On 01/22/2018 09:18 AM, Randy Li wrote:
>>>>
>>> Also the power domain driver could manage the clocks as well, I would
>>> suggest to use pm_runtime_*.
>>
>> actually the clocks required by pm domain may not be the same as what we
>> want to control here, there might be some clocks only be needed when
>> accessing mmu registers.
>>
>> but i'm not very sure about that, will confirm it with Simon Xue.
> 
> confirmed with Simon, there might be some iommus don't have a pd, and 
We use the pd to control the NIU node(not on upstream), without a pd or 
fake pd, none of the platform would work.
> the CONFIG_PM could be disabled.I am hard to believe a modern platform can work without that.
> 
> so it might be better to control clocks in iommu driver itself.I won't insist how the version of the iommu patch on the upstream, I 
just post an idea here.
The version for kernel 4.4 is under internal review, the implementation 
has been modified many times.

I would suggest the managing clocks in pd is a more easy way and don't 
need to spare those thing in two places.
> 
> 
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> 

-- 
Randy Li