linux-kernel - Re: [PATCH v4 08/13] iommu/rockchip: Control clocks needed to access the IOMMU

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Message-ID: <c05d4794-b76d-cfaa-d7ed-c44108117ee2@rock-chips.com>
Date:   Thu, 25 Jan 2018 17:42:17 +0800
From:   Randy Li <randy.li@...k-chips.com>
To:     JeffyChen <jeffy.chen@...k-chips.com>, tfiga@...omium.org
Cc:     Robin Murphy <robin.murphy@....com>, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, xxm@...k-chips.com,
        Joerg Roedel <joro@...tes.org>, jcliang@...omium.org,
        linux-rockchip@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Heiko Stuebner <heiko@...ech.de>
Subject: Re: [PATCH v4 08/13] iommu/rockchip: Control clocks needed to access
 the IOMMU


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.
> 
> 
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip
> 

-- 
Randy Li

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