Re: [PATCH -v6 02/13] tracing: add mips_timecounter_read() for MIPS

[Wu Zhangjin <wuzhangjin@gmail.com>]

Hi Ralf, 

Could you please give some feedback on this patch?

Really looking forward to your feedback and then resend this patchset
out ;)

Thanks & Regards,
	Wu Zhangjin

On Mon, 2009-10-26 at 23:13 +0800, Wu Zhangjin wrote:
> This patch add a new function: mips_timecounter_read() to get high
> precision timestamp without extra lock.
> 
> It is based on the clock counter register and the
> timecounter/cyclecounter abstraction layer of kernel.
> 
> Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
> ---
>  arch/mips/include/asm/time.h |   19 +++++++++++++++++++
>  arch/mips/kernel/csrc-r4k.c  |   41 +++++++++++++++++++++++++++++++++++++++++
>  arch/mips/kernel/time.c      |    2 ++
>  3 files changed, 62 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/mips/include/asm/time.h b/arch/mips/include/asm/time.h
> index df6a430..b8af7fa 100644
> --- a/arch/mips/include/asm/time.h
> +++ b/arch/mips/include/asm/time.h
> @@ -73,8 +73,18 @@ static inline int mips_clockevent_init(void)
>   */
>  #ifdef CONFIG_CSRC_R4K_LIB
>  extern int init_r4k_clocksource(void);
> +extern int init_r4k_timecounter(void);
> +extern u64 r4k_timecounter_read(void);
>  #endif
>  
> +static inline u64 mips_timecounter_read(void)
> +{
> +#ifdef CONFIG_CSRC_R4K
> +	return r4k_timecounter_read();
> +#else
> +	return sched_clock();
> +#endif
> +}
>  static inline int init_mips_clocksource(void)
>  {
>  #ifdef CONFIG_CSRC_R4K
> @@ -84,6 +94,15 @@ static inline int init_mips_clocksource(void)
>  #endif
>  }
>  
> +static inline int init_mips_timecounter(void)
> +{
> +#ifdef CONFIG_CSRC_R4K
> +	return init_r4k_timecounter();
> +#else
> +	return 0;
> +#endif
> +}
> +
>  extern void clocksource_set_clock(struct clocksource *cs, unsigned int clock);
>  extern void clockevent_set_clock(struct clock_event_device *cd,
>  		unsigned int clock);
> diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
> index e95a3cd..4e7705f 100644
> --- a/arch/mips/kernel/csrc-r4k.c
> +++ b/arch/mips/kernel/csrc-r4k.c
> @@ -7,6 +7,7 @@
>   */
>  #include <linux/clocksource.h>
>  #include <linux/init.h>
> +#include <linux/sched.h>
>  
>  #include <asm/time.h>
>  
> @@ -36,3 +37,43 @@ int __init init_r4k_clocksource(void)
>  
>  	return 0;
>  }
> +
> +static struct timecounter r4k_tc = {
> +	.cc = NULL,
> +};
> +
> +static cycle_t r4k_cc_read(const struct cyclecounter *cc)
> +{
> +	return read_c0_count();
> +}
> +
> +static struct cyclecounter r4k_cc = {
> +	.read = r4k_cc_read,
> +	.mask = CLOCKSOURCE_MASK(32),
> +	.shift = 32,
> +};
> +
> +int __init init_r4k_timecounter(void)
> +{
> +	if (!cpu_has_counter || !mips_hpt_frequency)
> +		return -ENXIO;
> +
> +	r4k_cc.mult = div_sc((unsigned long)mips_hpt_frequency, NSEC_PER_SEC,
> +			32);
> +
> +	timecounter_init(&r4k_tc, &r4k_cc, sched_clock());
> +
> +	return 0;
> +}
> +
> +u64 r4k_timecounter_read(void)
> +{
> +	u64 clock;
> +
> +	if (r4k_tc.cc != NULL)
> +		clock = timecounter_read(&r4k_tc);
> +	else
> +		clock = sched_clock();
> +
> +	return clock;
> +}
> diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
> index 1f467d5..e38cca1 100644
> --- a/arch/mips/kernel/time.c
> +++ b/arch/mips/kernel/time.c
> @@ -156,4 +156,6 @@ void __init time_init(void)
>  
>  	if (!mips_clockevent_init() || !cpu_has_mfc0_count_bug())
>  		init_mips_clocksource();
> +	if (!cpu_has_mfc0_count_bug())
> +		init_mips_timecounter();
>  }