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    SubjectRe: [PATCH v11 17/27] iommu/exynos: remove calls to Runtime PM API functions
    On Wed, 19 Mar 2014 19:51:21 +0100, Tomasz Figa wrote:
    > On 19.03.2014 19:37, Grant Grundler wrote:
    > > On Wed, Mar 19, 2014 at 10:30 AM, Tomasz Figa <t.figa@samsung.com> wrote:
    > > ...
    > >> As I said, AFAIK the trend is to get rid of ordering by initcalls and make
    > >> sure that drivers can handle missing dependencies properly, even for
    > >> "services" such as DMA, GPIO, clocks and so on, which after all are provided
    > >> by normal drivers like other.
    > >
    > > Ok - I'm not following the general kernel dev trends. initcall()
    > > levels are easy to understand and implement. So I would not be in a
    > > hurry to replace them.
    > >
    >
    > Well, initcall level is still a way to satisfy most of dependencies,
    > i.e. all client devices with higher initcall levels will probe
    > successfully. However the other case needs to be handled as well - in
    > this case the IOMMU binding code needs to defer probe of client driver
    > if respective IOMMU is not yet available.

    I now understand what is deferred probing you mentioned.
    However, I worry that many existing drivers are not ready
    for deferred probing.

    But still I wonder if System MMU driver need to be probed in the same
    initcall level.

    > >>> ps. I've written IOMMU support for four different IOMMUs on three
    > >>> operating systems (See drivers/parisc for two linux examples). But I
    > >>> still feel like I at best have 80% understanding of how this one is
    > >>> organized/works. Abstract descriptions and convoluted code have been
    > >>> handicapping me (and lack of time to dig further).
    > >>
    > >>
    > >> Well, this is one of my concerns with this driver. It isn't easy to read
    > >> (and so review, maintain, extend and debug found issues).
    > >
    > > My postscript comment was more to explain why I'm not confident in my
    > > opinion - not a reason to reject the patch series. I still consider
    > > the whole series as a step forward. But I'm not the expert here.
    >
    > I fully agree with you. Other than the issues mentioned in review, the
    > patches are definitely a step forward. I'd even say that all the patches
    > that have nothing to do with device tree could be merged in their
    > current form and the code refined later. It doesn't mean that patches
    > shouldn't be reviewed now and issues spotted reported, even if they
    > could be fixed later - this is for the IOMMU subsystem maintainer to decide.
    >
    > As for patches related to DT support, more care needs to be taken, as
    > bindings should be designed with stability in mind, so the refining
    > process should happen at review stage.
    >
    > > Right now, with ~30 patches posted by the exynos iommu (official?)
    > > maintainer, no one else who has a clue will attempt to fix or clean up
    > > those kinds of problems. i.e. it's useful to enable others to fix
    > > what are essentially unspecified "design pattern" issues.
    >
    > Agreed.

    Let me wait for the way of binding System MMU and its master developed by Marek.

    Regards,

    KyongHo


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