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From: Ingo Molnar <mingo@elte.hu>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Typo in x86 apic.c with DIVISOR setup
Date: Fri, 10 Oct 2008 11:01:00 +0200	[thread overview]
Message-ID: <20081010090100.GC319@elte.hu> (raw)
In-Reply-To: <aa79d98a0810092239p32153776qd0cda47e54929545@mail.gmail.com>


* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> Ah, it was CONFG who is guilty :) This is true indeed, thanks!

yeah.

> But here is not the same
> 
>        apic_write(APIC_TDCR,
>                (tmp_value & ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE)) |
> -               APIC_TDR_DIV_16);
> +               APIC_TDR_DIV);
> 
> On x86_64 it will be 1 now but we've used 16 for a long time in 
> purpose to slowdown processor's bus CLKs from APIC point of view. So I 
> don't think it's good idea to change it now. If we start using divisor 
> 1 today -- it would work for some time 'till processor bus raised to 
> the some speed when we'll get counter underflow before calibration 
> finished.
> 
> So could you please split the patch into two:
> 1) Plain CONFG typo fix (which is completely Ack'ed)
> 2) APIC divisor patch (which I'm not sure if we've to touch)

okay, since we typoed that CONFG thing (sidenote: we really need a 
.config flag that will start a grep that fails the build if there's a 
non-existent CONFIG option anywhere in the tree), we basically tested 
the divisor of 16 on a wide range of boxes.

So .. how about just standardizing on the divisor of 16 on both 32-bit 
and 64-bit?

	Ingo

  reply	other threads:[~2008-10-10  9:01 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-10  0:22 [PATCH] Typo in x86 apic.c with DIVISOR setup Venki Pallipadi
2008-10-10  4:38 ` Cyrill Gorcunov
2008-10-10  5:10   ` Pallipadi, Venkatesh
2008-10-10  5:39     ` Cyrill Gorcunov
2008-10-10  9:01       ` Ingo Molnar [this message]
2008-10-10 11:14         ` Cyrill Gorcunov
2008-10-10 11:15         ` Maciej W. Rozycki
2008-10-10 11:16         ` Cyrill Gorcunov
2008-10-10 11:24           ` Maciej W. Rozycki
2008-10-10 11:56             ` Ingo Molnar
2008-10-10 12:38               ` Cyrill Gorcunov
2008-10-10 14:45                 ` Ingo Molnar
2008-10-10 12:26             ` Cyrill Gorcunov
2008-10-10 16:01       ` Pallipadi, Venkatesh
2008-10-10 16:29         ` Maciej W. Rozycki

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