linux-kernel - Re: [PATCH 1/9] iommu/of: Drop early initialisation hooks

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Date:   Fri, 12 Jan 2018 09:22:06 +0800
From:   JeffyChen <jeffy.chen@...k-chips.com>
To:     Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org
CC:     jcliang@...omium.org, tfiga@...omium.org,
        linux-samsung-soc@...r.kernel.org, Kukjin Kim <kgene@...nel.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        iommu@...ts.linux-foundation.org,
        Frank Rowand <frowand.list@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/9] iommu/of: Drop early initialisation hooks

Hi Robin,

Thnaks for your reply.

On 01/11/2018 08:24 PM, Robin Murphy wrote:
> Hi Jeffy,
>
> On 11/01/18 11:14, JeffyChen wrote:
>> Hi Marek,
>>
>> Thanks for your reply.
>>
>> On 01/11/2018 05:40 PM, Marek Szyprowski wrote:
>>> Hi Jeffy,
>>>
>>> On 2018-01-11 09:22, Jeffy Chen wrote:
>>>> With the probe-deferral mechanism, early initialisation hooks are no
>>>> longer needed.
>>>>
>>>> Suggested-by: Robin Murphy <robin.murphy@....com>
>
> In fact, shortly after I said that I had a "how hard can it be?" moment
> and took a crack at it myself - sorry, I should probably have cc'd you
> on that series[1].

hmmm, i'll drop this patch in the next version.

and maybe rebase my patch[9] (iommu/rockchip: Use OF_IOMMU to attach 
devices automatically) on that series
>
>>>> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
>>>> ---
>>>>
>>>>   drivers/iommu/arm-smmu-v3.c  |  2 +-
>>>>   drivers/iommu/arm-smmu.c     | 12 ++++++------
>>>>   drivers/iommu/exynos-iommu.c |  2 +-
>>>
>>> For Exynos IOMMU:
>>> Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>>
>>> IPMMU and MSM IOMMU are no longer multi-platform safe after this patch.
>>> It breaks them in the same way as my commit 928055a01b3f ("iommu/exynos:
>>> Remove custom platform device registration code") broke Exynos IOMMU.
>>>
>>> You need a similar fix for them:
>>> https://www.spinics.net/lists/arm-kernel/msg627648.html
>>
>> hmmm, right, i did saw this fix in the rockchip iommu driver too.
>>
>> and there're also some other iommu drivers put bus_set_iommu in their
>> probe() to avoid that.
>>
>> maybe we can do it in the iommu framework?
>>
>> for example:
>> 1/ add a bus type member to struct iommu_device
>> 2/ and a iommu_device_set_bus()
>> 3/ do the bus_set_iommu stuff in iommu_device_register()
>> 4/ undo bus_set_iommu in iommu_device_unregister()
>
> Ultimately we'd like to get rid of the bus relationship altogether, so I
> don't think it's really worth adding more infrastructure around it.
> Having of-iommu-based drivers set bus ops at probe time, and others
> conditionally from an initcall, is pretty clean and simple, so I'd
> rather stick with that approach for now.
ok, make sense:)
>
> Robin.
>
> [1]
> https://lists.linuxfoundation.org/pipermail/iommu/2018-January/025395.html
>
>
>