linux-kernel - Re: [RFC] clocksouce implementation for powerpc

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Date:	Fri, 22 Jun 2007 16:10:47 +1000
From:	tony@...eyournoodle.com (Tony Breeds)
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	Daniel Walker <dwalker@...sta.com>, Andrew Morton <akpm@...l.org>,
	john stultz <johnstul@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	LinuxPPC-dev <linuxppc-dev@...abs.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC] clocksouce implementation for powerpc

On Wed, Jun 20, 2007 at 08:53:47PM +0400, Sergei Shtylyov wrote:

Hi Sergei,
	Thanks for taking the time to look over my patch.

>    I guess it's been based on the prior work by John Stultz (and me too :-)?

At some level I guess so.  John did send me a patch a while ago.
 
>    If you mean the init. part, this has been already done by me -- I've 
> implemented read_persistent_clock() and got rid of xtime setting. What's 
> left is to implemet update_persistent_clock() and get rid of 
> timer_check_rtc()...

Actually I think that comment is redundant.  and should be removed
sorry.

>    Perhaps we even need to raise the rating to 300 or 400 -- according to 
> what <linux/clocksource.h> says?

Sure.
 
> >+	.flags        = CLOCK_SOURCE_IS_CONTINUOUS,
> >+	.mask         = CLOCKSOURCE_MASK(64),
> >+	.shift        = 22,
> 
>    PPC64 has issues with the fixed shift value, see:
> 
> http://patchwork.ozlabs.org/linuxppc/patch?id=11125

Thanks!
 
> >+	.mult         = 0,	/* To be filled in */
> >+	.read         = NULL,   /* To be filled in */
> >+	.settimeofday = NULL,   /* To be filled in */
> 
>    I don't quite understand why not just init them right away?  The values 
> are fixed anyways.

Well at least mult needs to be calculated at runtime, and I prefer to
have the structure near the top of the file at which stage the
read/settimeofday functions aren't defined.

Yours Tony

  linux.conf.au        http://linux.conf.au/ || http://lca2008.linux.org.au/
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