linux-kernel - Re: PATCH: Allow user to force 'tsc' to be treated as stable.

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Date:	Fri, 6 Feb 2009 15:36:46 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Ben Greear <greearb@...delatech.com>
cc:	linux-kernel <linux-kernel@...r.kernel.org>, rusty@...tcorp.com.au
Subject: Re: PATCH:  Allow user to force 'tsc' to be treated as stable.

On Thu, 5 Feb 2009, Ben Greear wrote:

> Allow user to force TSC as stable clock-source. Works around BIOS issues 
> in the FWA-7304 (Via CN700 chipset) system, and possibly others.

How do you know that the TSC is stable on such system? What was the reason 
for kernel marking it unstable?

> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index ca89e15..0578fcb 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -54,6 +54,7 @@ static LIST_HEAD(clocksource_list);
>  static DEFINE_SPINLOCK(clocksource_lock);
>  static char override_name[32];
>  static int finished_booting;
> +static int force_tsc_stable;
>  
>  /* clocksource_done_booting - Called near the end of core bootup
>   *
> @@ -82,6 +83,14 @@ static unsigned long watchdog_resumed;
>  #define WATCHDOG_INTERVAL (HZ >> 1)
>  #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
>  
> +static int __init parse_force_tsc_stable(char *arg)
> +{
> +	force_tsc_stable = 1;
> +	return 0;
> +}
> +early_param("force_tsc_stable", parse_force_tsc_stable);

Documentation/kernel-parameters.txt would also like to know about this 
option.

-- 
Jiri Kosina
SUSE Labs

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