From: shinya.kuribayashi.px@renesas•com (Shinya Kuribayashi)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 2/2] ARM: delay: allow timer-based delay implementation to be selected
Date: Thu, 05 Jul 2012 21:12:14 +0900 [thread overview]
Message-ID: <4FF5849E.6060301@renesas.com> (raw)
In-Reply-To: <20120704153624.GI15104@mudshark.cambridge.arm.com>
Hi Will,
On 7/5/2012 12:36 AM, Will Deacon wrote:
>> If we use 'lpj_fine' for this, we need to skip secondary CPU calibration
>> explicitly in another way, something like this:
>>
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-January/039506.html
>> [PATCH 5/5] ARM: smp: Skip secondary cpu calibration to speed-up boot
>
> How about keeping it simple like this:?
>
>
> diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
> index e1030e1..84bb5da 100644
> --- a/arch/arm/lib/delay.c
> +++ b/arch/arm/lib/delay.c
> @@ -63,4 +63,9 @@ void __init init_current_timer_delay(unsigned long freq)
> arm_delay_ops.const_udelay = __timer_const_udelay;
> arm_delay_ops.udelay = __timer_udelay;
> }
> +
> +unsigned long __cpuinit calibrate_delay_is_known(void)
> +{
> + return lpj_fine ?: 0;
> +}
> #endif
Thanks for the patch, looks lika a missing piece of CPU calibration
optimization for SMP platforms in the face of core frequency scaling.
Ok, I gave your patch a try (including above), and confirmed that:
* It works fine with non-arch_timer counter. I'm using SH/R-Mobile
devices, with a memory mapped I/O, 32-bit free-run up-counter
running at 13MHz.
* Secondary CPU calibration gets skipped as expected.
* Your new timer-based delay works as before (loop-based one). I've
verified 10..1999-microsecond busy-wait with a reasonable accuracy
(and confirmed that 2000+ usec gets rejected as intended).
By the way,
> + return lpj_fine ?: 0;
Is there any difference with just
return lpj_fine;
?
next prev parent reply other threads:[~2012-07-05 12:12 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-29 17:33 [PATCH v2 0/2] Use architected timers for delay loop Will Deacon
2012-06-29 17:33 ` [PATCH v2 1/2] ARM: arch timer: implement read_current_timer and get_cycles Will Deacon
2012-07-02 19:14 ` Stephen Boyd
2012-07-05 12:35 ` Shinya Kuribayashi
2012-07-05 12:59 ` Will Deacon
2012-06-29 17:33 ` [PATCH v2 2/2] ARM: delay: allow timer-based delay implementation to be selected Will Deacon
2012-07-02 19:14 ` Stephen Boyd
2012-07-02 21:53 ` Will Deacon
2012-07-03 12:09 ` Shinya Kuribayashi
2012-07-04 15:36 ` Will Deacon
2012-07-05 12:12 ` Shinya Kuribayashi [this message]
2012-07-05 12:56 ` Will Deacon
2012-07-05 16:51 ` Stephen Boyd
2012-07-05 13:06 ` Shinya Kuribayashi
2012-07-05 14:15 ` Will Deacon
2012-07-12 7:33 ` Shinya Kuribayashi
2012-07-12 8:44 ` Will Deacon
2012-07-12 9:35 ` Shinya Kuribayashi
2012-07-12 16:40 ` Stephen Boyd
2012-07-13 2:16 ` Shinya Kuribayashi
2012-07-13 8:57 ` Will Deacon
2012-07-13 10:48 ` Shilimkar, Santosh
2012-07-13 11:13 ` Will Deacon
2012-07-13 12:04 ` Shilimkar, Santosh
2012-07-13 12:08 ` Will Deacon
2012-07-13 12:14 ` Shilimkar, Santosh
2012-07-13 12:23 ` Will Deacon
2012-07-13 12:28 ` Shilimkar, Santosh
2012-07-17 3:10 ` Shinya Kuribayashi
2012-07-17 6:11 ` Shilimkar, Santosh
2012-07-17 7:42 ` Shinya Kuribayashi
2012-07-17 9:05 ` Will Deacon
2012-07-19 12:43 ` Shinya Kuribayashi
2012-07-18 17:52 ` Will Deacon
2012-07-19 15:19 ` Jonathan Austin
2012-07-20 10:17 ` Will Deacon
2012-07-24 9:06 ` Shinya Kuribayashi
2012-07-24 9:15 ` Will Deacon
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