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    SubjectRe: [PATCH 17/26] ARM: pxa: pxa95x is incompatible with earlier pxa
    On Sun, Oct 9, 2011 at 2:21 PM, Haojian Zhuang <haojian.zhuang@gmail.com> wrote:
    > On Sat, Oct 8, 2011 at 9:24 PM, Arnd Bergmann <arnd@arndb.de> wrote:
    >> On Saturday 08 October 2011 11:32:14 Haojian Zhuang wrote:
    >>>
    >>> Eric,
    >>>
    >>> At first, a new macro (ARCH_PXA_V7) is defined in
    >>> arch/arm/mach-pxa/Kconfig in this patch.
    >>> I prefer to move this macro to arch/arm/Kconfig.
    >>
    >> If we move it to arch/arm/Kconfig, I would prefer making it a global option,
    >> not a pxa specific one. If we introduce a top-level CONFIG_CPU_V6PLUS
    >> option, we can make a number of decisions inside of Kconfig depend on that,
    >> especially as we move to allow building multiple v6/v7 platforms together,
    >> or multiple v5 platforms for that matter. I believe we don't need to
    >> worry about v5+v7 at this point and can instead assume that won't ever
    >> happen.
    >>
    > Nobody is using PJ4 as v6 architecture now. CPUv6 is used in old stepping
    > of Dove and MMP2. CPU_PJ4 only enables CPU_v7 in the mainline code.
    >
    > If we used ARCH_PXA_V7 in arch/arm/Kconfig, we would have two ARCH for
    > pxa. One is ARCH_PXA, and the other is ARCH_PXA_V7. Those v5 machine
    > should be based on ARCH_PXA. And the saarb, tavorevb3 should be based
    > on ARCH_PXA_V7. So we can avoid to define PXA_V7_MACH_AUTO. I think
    > the logic of Kconfig could be easier.

    Haojian,

    PXA_V7_MACH_AUTO is to by default auto enable tavorevb3 when
    ARCH_PXA_V7 is selected.

    >
    >>> Secondly, pxa95x is both used in saarb and tavorevb3.
    >>
    >> The patch makes that very explicit, doesn't it?
    >>
    > +config PXA_V7_MACH_AUTO
    > +       def_bool y
    > +       depends on ARCH_PXA_V7
    > +       depends on !MACH_SAARB
    > +       select MACH_TAVOREVB3
    > +
    >
    > Please check this. In your patch, SAARB and TAVOREVB3 is a mutex.

    They are actually not mutually exclusive - it's a trick we use to select
    MACH_TAVOREVB3 by default but this option also disappears once SAARB
    is selected.

    Arnd,

    The 'depends on ARCH_PXA_V7' could actually be removed here, as the
    option is already encapsulated in if ARCH_PXA_V7 ... endif. And this
    trick won't work very well when there are more than 2 boards.

    >
    >>> Thirdly, PXA_V7_MACH_AUTO is unnecessary. We just need to select those
    >>> machines in defconfig or define a new DT machine type to select all
    >>> machines.
    >>
    >> Enabling them in defconfig will not help here, it still allows creating
    >> an invalid configuration by disabling both saarb and tavorevb3.
    >> I agree that it would be best to have a single DT machine type that can
    >> handle both saarb and tavorevb3 as well as any future pxa95x based machines,
    >> but nobody has implemented that yet. In the meantime, I think we should
    >> have the PXA_V7_MACH_AUTO or an equivalent mechanism to enforce that at
    >> least one of the two board files gets built into any kernel. This is mostly
    >> important to help the 'make randconfig' builds succeed, not for actual
    >> users getting it wrong accidentally.
    >>
    >>        Arnd
    >>
    >
    > Exactly we need to define a single DT machine type in both arch-pxa
    > and arch-mmp.
    > I'll register it first.

    Please go ahead.
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