From: robherring2@gmail.com (Rob Herring)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/3] ARM sched_clock selection enhancements
Date: Tue, 12 Mar 2013 07:43:58 -0500 [thread overview]
Message-ID: <513F230E.1030307@gmail.com> (raw)
In-Reply-To: <20130312092358.GP4977@n2100.arm.linux.org.uk>
On 03/12/2013 04:23 AM, Russell King - ARM Linux wrote:
> On Mon, Mar 11, 2013 at 09:26:34PM -0500, Rob Herring wrote:
>> In preparation to move more timer initialization to use CLKSRC_OF and
>> out of the platforms, a way to select the timer used for sched_clock is
>> needed. This series makes the ARM sched_clock support code prefer 64-bit
>> counters or higher frequency counters. This is sufficient at least on
>> ARM Ltd boards to use the 24MHz counter rather than sp804 and to always
>> use the 64-bit architected timer when present. This mechanism can be
>> extended to DT properties if needed for any non-discoverable h/w feature.
>
> No - this stuff is designed specifically to cope with the dilemas of
> less-than-64-bit sched_clock sources. If you have 64-bit sources, then
> that should be dealt with differently - this code will break with 64-bit
> sources due to the multiplication and shift losing the high order bits.
It is dealt with differently. In the 64-bit case, there is only a
multiply and all the code to deal with wrapping of 32-bit counters is
skipped. It is exactly the same conversion as arm64.
Rob
next prev parent reply other threads:[~2013-03-12 12:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 2:26 [PATCH 0/3] ARM sched_clock selection enhancements Rob Herring
2013-03-12 2:26 ` [PATCH 1/3] ARM: sched_clock: allow changing to higher frequency counter Rob Herring
2013-03-12 2:26 ` [PATCH 2/3] ARM: sched_clock: support 64-bit counters Rob Herring
2013-03-21 14:02 ` Christopher Covington
2013-03-21 22:15 ` Rob Herring
2013-03-22 12:03 ` Christopher Covington
2013-03-22 12:58 ` Rob Herring
2013-03-22 15:20 ` Russell King - ARM Linux
2013-03-22 11:09 ` Russell King - ARM Linux
2013-03-12 2:26 ` [PATCH 3/3] ARM: arch_timer: use the 64-bit sched_clock setup Rob Herring
2013-03-12 9:23 ` [PATCH 0/3] ARM sched_clock selection enhancements Russell King - ARM Linux
2013-03-12 12:43 ` Rob Herring [this message]
2013-03-20 23:03 ` Rob Herring
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