Re: [PATCH v5] MIPS: Add a high resolution sched_clock() via cnt32_to_63().

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Wu Zhangjin wrote:

> From: Wu Zhangjin <wuzhangjin@gmail.com>

> (This v5 revision incorporates with the feedbacks from Ingo.)

> This patch adds a cnt32_to_63() and MIPS c0 count based sched_clock(),
> which provides high resolution. and also, one new kernel option
> (HR_SCHED_CLOCK) is added to enable/disable this sched_clock().

> Without it, the Ftrace for MIPS will give useless timestamp information.

> Because cnt32_to_63() needs to be called at least once per half period
> to work properly, Differ from the old version, this v2 revision set up a
> kernel timer to ensure the requirement of some MIPSs which have short c0
> count period.

> Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>

> diff --git a/arch/mips/kernel/csrc-r4k-hres.c b/arch/mips/kernel/csrc-r4k-hres.c
> new file mode 100644
> index 0000000..2fe8be7
> --- /dev/null
> +++ b/arch/mips/kernel/csrc-r4k-hres.c

    I don't think this is really good name for this file (one might think 
that this is another implementation of clocksource instead of some 
sched_clock() code tied to this particular clocksource), and I don't think 
we indeed needed to separate that thing into a file of its own, i.e. I'm 
against Ingo's suggestion in this case.

WBR, Sergei