linux-kernel - Re: [PATCH v7 6/6] x86/tsc: use tsc early

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Date:   Fri, 3 Nov 2017 10:54:26 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>,
        <steven.sistare@...cle.com>, <daniel.m.jordan@...cle.com>,
        <linux@...linux.org.uk>, <schwidefsky@...ibm.com>,
        <heiko.carstens@...ibm.com>, <john.stultz@...aro.org>,
        <sboyd@...eaurora.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <mingo@...hat.com>,
        <tglx@...utronix.de>, <hpa@...or.com>
Subject: Re: [PATCH v7 6/6] x86/tsc: use tsc early

Hi Pavel,

At 11/03/2017 01:26 AM, Pavel Tatashin wrote:
> tsc_early_init():
> Determines offset, shift and multiplier for the early clock based on the
> TSC frequency.
>
> tsc_early_fini()
> Implement the finish part of early tsc feature, prints message about the
> offset, which can be useful to find out how much time was spent in post and
> boot manager (if TSC starts from 0 during boot)
>
> sched_clock_early():
> TSC based implementation of early clock.
>
> Call tsc_early_init() to initialize early boot time stamps functionality on
> the supported x86 platforms, and call tsc_early_fini() to finish this
> feature after permanent clock has been initialized.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> ---
>  arch/x86/include/asm/tsc.h |  4 +++
>  arch/x86/kernel/setup.c    | 10 ++++--
>  arch/x86/kernel/time.c     |  1 +
>  arch/x86/kernel/tsc.c      | 81 ++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 94 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
> index f5e6f1c417df..6dc9618b24e3 100644
> --- a/arch/x86/include/asm/tsc.h
> +++ b/arch/x86/include/asm/tsc.h
> @@ -50,11 +50,15 @@ extern bool tsc_store_and_check_tsc_adjust(bool bootcpu);
>  extern void tsc_verify_tsc_adjust(bool resume);
>  extern void check_tsc_sync_source(int cpu);
>  extern void check_tsc_sync_target(void);
> +void tsc_early_init(unsigned int khz);
> +void tsc_early_fini(void);
>  #else
>  static inline bool tsc_store_and_check_tsc_adjust(bool bootcpu) { return false; }
>  static inline void tsc_verify_tsc_adjust(bool resume) { }
>  static inline void check_tsc_sync_source(int cpu) { }
>  static inline void check_tsc_sync_target(void) { }
> +static inline void tsc_early_init(unsigned int khz) { }
> +static inline void tsc_early_fini(void) { }
>  #endif
>
>  extern int notsc_setup(char *);
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 0957dd73d127..3df8be642b80 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -822,7 +822,11 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
>  	return 0;
>  }
>
> -static void __init simple_udelay_calibration(void)
> +/*
> + * Initialize early tsc to show early boot timestamps, and also loops_per_jiffy
> + * for udelay
> + */
> +static void __init early_clock_calibration(void)

Commit:

eb496063c990 ("x86/timers: Move the simple udelay calibration to tsc.h")

moves this function to tsc.h and renames it in tip tree[1].

I guess using this commit, we can simplify this patch.

As this series, except the 2rd patch, is worked for x86, how about let
this series be based on tip.

BTW, I am testing your patches, will give you result later.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git

Thanks,
	dou