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From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 06/11] ARM: vexpress: use clocksource_of_init for sp804
Date: Fri, 15 Mar 2013 12:34:08 +0000
Message-ID: <20130315123408.GJ4977@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <5140AA01.1010007@gmail.com>

On Wed, Mar 13, 2013 at 11:32:01AM -0500, Rob Herring wrote:
> If you have 2 sp804's, why do you care which one is used by the OS? If
> they are identical, then it doesn't matter. If they are not, then
> describe how they are not identical.
> 
> The realview and versatile boards currently do this, but there is no
> good reason that I see and I intend to change this.

It is highly likely that the timer choice on these boards was made by
independent people, who came up with different random choices.  Nothing
more than that - I believe it to be entirely arbitary.  I do think
discussion is getting too bogged down on this point.

So, we could make the decision about which timer to use for the clock
event based on whether an interrupt is specified, the known clock rate
and size of the timer register.

Same can be done for the clock source, but preferring a timer without
an interrupt in preference to one with an interrupt.

We do have this nice rating system for clocksources and clockevents -
and it could be more flexible if it didn't separate clocksources from
clockevents - allowing just a single "timer" and marking it as being
suitable as a clocksource or a clockevent, or indeed both.

However, for SP804 selection, there are cases where it matters, such as
on Versatile Express where you have to select the right set of SP804 to
have a working system (because ARM didn't fully document the SP804 setup
there) and we have no way to switch some of those timers from their
32kHz clock source.  But then we could just omit the clock source for
the "bad" SP804s which would prevent them being used.

  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-13  5:05 [PATCH v3 00/11] add hisilicon SoC support Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 01/11] clocksource: move sp timer driver Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 02/11] clocksource: select USE_OF by default Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 03/11] clocksource: sp804: add device tree support Haojian Zhuang
2013-03-13 11:05   ` Pawel Moll
2013-03-13 11:37     ` Haojian Zhuang
2013-03-13 11:41       ` Pawel Moll
2013-03-13 14:17     ` Rob Herring
2013-03-13 14:42       ` Pawel Moll
2013-03-13 14:51         ` Rob Herring
2013-03-13 14:55           ` Pawel Moll
2013-03-13 15:11             ` Haojian Zhuang
2013-03-13 15:23               ` Pawel Moll
2013-03-13 15:25                 ` Haojian Zhuang
2013-03-13 15:29                   ` Pawel Moll
2013-03-13 15:39                     ` Rob Herring
2013-03-13 15:41                       ` Pawel Moll
2013-03-13 15:44                         ` Haojian Zhuang
2013-03-13 15:42                     ` Haojian Zhuang
2013-03-13 15:49                       ` Pawel Moll
2013-03-13 16:35                         ` Arnd Bergmann
2013-03-13 16:41                           ` Pawel Moll
2013-03-15 12:20       ` Russell King - ARM Linux
2013-03-13  5:05 ` [PATCH v3 04/11] ARM: integrator: use clocksource_of_init for sp804 Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 05/11] ARM: highbank: " Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 06/11] ARM: vexpress: " Haojian Zhuang
2013-03-13 11:10   ` Pawel Moll
2013-03-13 11:42     ` Haojian Zhuang
2013-03-13 11:46       ` Pawel Moll
2013-03-13 12:21         ` Haojian Zhuang
2013-03-13 14:48           ` Pawel Moll
2013-03-13 15:01             ` Haojian Zhuang
2013-03-13 15:19               ` Pawel Moll
2013-03-13 15:59                 ` Haojian Zhuang
2013-03-13 16:28                   ` Pawel Moll
2013-03-13 16:32                   ` Rob Herring
2013-03-15 12:34                     ` Russell King - ARM Linux [this message]
2013-03-15 12:58                       ` Pawel Moll
2013-03-15 18:10                         ` Russell King - ARM Linux
2013-03-13  5:05 ` [PATCH v3 07/11] ARM: debug: support debug ll on hisilicon soc Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 08/11] clk: hi3xxx: add clock support Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 09/11] ARM: hi3xxx: add board support with device tree Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 10/11] ARM: hi3xxx: enable hi4511 " Haojian Zhuang
2013-03-13  5:05 ` [PATCH v3 11/11] ARM: config: append arch hi3xxx into multi defconfig Haojian Zhuang

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