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: Tue, 03 Jul 2012 21:09:31 +0900 [thread overview]
Message-ID: <4FF2E0FB.4040008@renesas.com> (raw)
In-Reply-To: <1340991231-17682-3-git-send-email-will.deacon@arm.com>
Hello,
On 6/30/2012 2:33 AM, Will Deacon wrote:
> implemented in terms of read_current_timer. This further allows us to
> skip the loop calibration and have a consistent delay function in the
> face of core frequency scaling.
[...]
> diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
> new file mode 100644
> index 0000000..e1030e1
> --- /dev/null
> +++ b/arch/arm/lib/delay.c
> @@ -0,0 +1,66 @@
[...]
> +void __init init_current_timer_delay(unsigned long freq)
> +{
> + pr_info("Switching to timer-based delay loop\n");
> + lpj_fine = freq / HZ;
Looking at init/calibrate.c, 'lpj_fine' can save the first loop
calibration, but does not save the second and subsequent calls to
calibrate_delay().
Magnus first noticed this, and changed to use 'preset_lpj' instead.
See the commit 173bf69a7a (ARM / mach-shmobile: Use preset_lpj with
calibrate_delay(), 2012-05-10).
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
I've been using Stephen's read_current_timer implemented + lpj_fine +
Santosh's skip secondary calibration combo for over a year, because I
wanted to save 'preset_lpj' for the original purpose, FWIW.
Shinya
> + arm_delay_ops.delay = __timer_delay;
> + arm_delay_ops.const_udelay = __timer_const_udelay;
> + arm_delay_ops.udelay = __timer_udelay;
> +}
> +#endif
next prev parent reply other threads:[~2012-07-03 12:09 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 [this message]
2012-07-04 15:36 ` Will Deacon
2012-07-05 12:12 ` Shinya Kuribayashi
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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