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Date:   Mon, 18 Jan 2010 10:08:32 -0800
From:   David Daney <ddaney@caviumnetworks.com>
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To:     wuzhangjin@gmail.com
CC:     Ralf Baechle <ralf@linux-mips.org>,
        Sergei Shtylyov <sshtylyov@ru.mvista.com>,
        David Daney <david.s.daney@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, linux-mips@linux-mips.org
Subject: Re: [PATCH v6] MIPS: Add a high resolution sched_clock() via cnt32_to_63().
References: <1259319110-16107-1-git-send-email-wuzhangjin@gmail.com> <1263801284.11671.50.camel@falcon>
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Wu Zhangjin wrote:
> If the processor support dynamic cpu frequency and the support is
> enabled in kernel, this sched_clock() implementation will be broken(and
> If the frequency of the MIPS CP0 counter is related to the cpu's
> frequency).
> 
> So, some extra resitrictions should be added to it.
> 
> arch/mips/Kconfig
> 
> config CPU_HAS_FIXED_CP0_COUNTER
> 	bool
> 
> config SYS_SUPPORTS_HRES_SCHED_CLOCK
> 	bool
> 	depends on CPU_HAS_FIXED_CP0_COUNTER || !CPU_FREQ
> 
> arch/mips/kernel/csrc-r4k.c
> 
> #ifdef SYS_SUPPORTS_HRES_SCHED_CLOCK
> 
> /* The high resolution version of sched_clock() */
> 
> #endif
> 
> And I'm not sure whether the cavium octeon support dynamic cpu
> frequency,

Not currently...

> if yes, it's high resolution version of sched_clock() also
> should be wrapped with the above macro to ensure it is not broken:
> 
> arch/mips/cavium-octeon/csrc-octeon.c
> 

... So this is not applicable.


> Regards,
> 	Wu Zhangjin
>