From: robherring2@gmail.com (Rob Herring)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/3] ARM sched_clock selection enhancements
Date: Wed, 20 Mar 2013 18:03:29 -0500 [thread overview]
Message-ID: <514A4041.9090406@gmail.com> (raw)
In-Reply-To: <513F230E.1030307@gmail.com>
Russell,
On 03/12/2013 07:43 AM, Rob Herring wrote:
> 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.
Do you have any further comments?
Rob
prev parent reply other threads:[~2013-03-20 23:03 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
2013-03-20 23:03 ` Rob Herring [this message]
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