Re: [PATCH 17/26] ARM: pxa: pxa95x is incompatible with earlier pxa

[Haojian Zhuang]

On Sun, Oct 9, 2011 at 2:36 PM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:
> On Sun, Oct 9, 2011 at 2:21 PM, Haojian Zhuang <haojian.zhuang@xxxxxxxxx> wrote:
>> On Sat, Oct 8, 2011 at 9:24 PM, Arnd Bergmann <arnd@xxxxxxxx> 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.
>ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA7iMTlInbItkRaH3yJidg18Bg1SyIYZhbgu4jKpRkG4vavWebU6FwjovIuXoJqWzQimP4dvF4LWVq1xW84jtds8hRIc0a9nI1o2DUyqFzYvHHbqjXq+AJCqmUCaf9mlGn5/Ocd4LDbZKff3rHApCZrP4J/5beIiBDX25sFyRPNFjakJp5FbqwT17L91900rj7O60UeTe/vI9Gaf/oIvxMYriDmF02vsQgNqVNUzFllB8VTVb5HprZFZFX0ulBWhgTfMNqrhcZAxKwAW8tAY2zqa7NZZQhw0Ea8IkZrwA4qAwjQHwY56mNL7JRFLKlLVt3dEfkgx/HHWS8v1D80VGXUw== zhouhong@zhouhong-desktop
> 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.
>
OK. Could I know why saarb should be deselected while tavorevb3 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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