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

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Date:   Mon, 22 Jan 2018 12:09:30 +0800
From:   JeffyChen <jeffy.chen@...k-chips.com>
To:     Randy Li <randy.li@...k-chips.com>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, tfiga@...omium.org
CC:     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

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 
the CONFIG_PM could be disabled.

so it might be better to control clocks in iommu driver itself.