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    SubjectRe: [PATCH v3 9/9] ARM: add initial support for Marvell Berlin SoCs
    On 11/08/2013 01:58 AM, Jisheng Zhang wrote:
    > On Thu, 7 Nov 2013 13:22:35 -0800
    > Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> wrote:
    >> On 11/07/2013 05:20 PM, Arnd Bergmann wrote:
    >>> On Thursday 07 November 2013, Sebastian Hesselbarth wrote:
    >>>> Actually, IIRC smp_twd does not compile without SMP set, so the above
    >>>> should at least be 'HAVE_ARM_TWD if SMP'. If you shrink MULTI_V7 down
    >>>> to non-SMP cores, you can disable it and it will fail to compile.
    >>>
    >>> If there are UP-systems for which TWD is the best clocksource, we should
    >>> probably fix the code to allow that configuration. IIRC there were already
    >>> patches recently in this area, maybe it's already solved.
    >
    > The problems is twd is not mandatory in CA9 UP system, so it may not exist.
    > However, I got answers from soc people, the BG2CD does configured and enabled
    > TWD. so we are lucky and can add HAVE_TWD for BG2CD.

    Jisheng,

    thanks for backing this up. As I said, I tried it with barebox and TWD
    is sufficient for a timer there.

    Currently, Linux requires SMP for TWD - but as you confirmed, there are
    non-SMP systems with TWD. The build errors below are just from a check
    for SMP systems, so if we remove that, TWD should be ready for non-SMP.

    I'll see, if I can prepare a patch next week and put it on list.

    Sebastian

    >> I just tried barebox bootloader to use TWD as timer on berlin2cd and it
    >> perfectly works, i.e. with time related commands I can see the timer
    >> register decreasing. So the timer is available on this UP SoC.
    >
    > Yep. It is available.
    >
    >>
    >> As said before, compiling linux without CONFIG_SMP but with
    >> CONFIG_HAVE_ARM_TWD gives:
    >>
    >> warning: (SOC_OMAP5 && ARCH_ROCKCHIP && ARCH_SHMOBILE_MULTI &&
    >> MACH_BERLIN_BG2 && MACH_BERLIN_BG2CD) selects HAVE_ARM_TWD which has
    >> unmet direct dependencies (SMP)
    >>
    >> and
    >>
    >> arch/arm/kernel/smp_twd.c: In function 'twd_local_timer_of_register':
    >> arch/arm/kernel/smp_twd.c:391: error: 'setup_max_cpus' undeclared (first
    >> use in this function)
    >> arch/arm/kernel/smp_twd.c:391: error: (Each undeclared identifier is
    >> reported only once
    >> arch/arm/kernel/smp_twd.c:391: error: for each function it appears in.)
    >> make[1]: *** [arch/arm/kernel/smp_twd.o] Error 1
    >>
    >> I haven't looked deeper into this, but I guess it will not be hard
    >> to make ARM_TWD independent of SMP.



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