From: gregory.clement@free-electrons•com (Gregory CLEMENT)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3 1/3] ARM: Introduce atomic MMIO modify
Date: Thu, 05 Sep 2013 11:20:19 +0200 [thread overview]
Message-ID: <52284CD3.7020804@free-electrons.com> (raw)
In-Reply-To: <20130905090841.GA9696@mudshark.cambridge.arm.com>
On 05/09/2013 11:08, Will Deacon wrote:
> On Thu, Sep 05, 2013 at 09:59:40AM +0100, Gregory CLEMENT wrote:
>> Hi all,
>
> Hi Gregory,
>
>> On 30/08/2013 12:03, Catalin Marinas wrote:
>>> On Fri, Aug 30, 2013 at 10:20:33AM +0100, Will Deacon wrote:
>>>> Perhaps we should just bit the bullet and define relaxed accessors for all
>>>> architectures? It's not difficult to default them to the non-relaxed
>>>> variants if the architecture doesn't provide an optimised implementation.
>>>
>>> Yes, an asm-generic default relaxed would be good (that's what I
>>> suggested earlier in this thread and it was discussed in the past). But
>>> no-one volunteered ;).
>>>
>>
>> I would like to make the things move on about this subject. Should it
>> be possible to merge this version of the patch set? Currently the
>> only users of this new API are drivers for ARM SoCs.
>
> In the short term then, I'd keep this restricted to ARM. Without relaxed
> accessors available across all architectures, I don't think we can make this
> usefully generic (a readX/writeX version would be horribly slow on ARM).
OK
>
>> In the meantime, I am willing to introduce an asm-generic default
>> relaxed variant of read and write, but as Catalin had already pointed
>> in the past
>> http://thread.gmane.org/gmane.linux.ports.arm.kernel/117626
>> it may take time to get an agreement from all the other architectures.
>
> I actually wrote those patches yesterday but, in doing so, I realised that
Great!
> the kernel doesn't have well-defined semantics for relaxed I/O accessors
> (i.e. different architectures use them to mean different things). That makes
> portability is an issue, even if the functions are defined everywhere.
It confirms that Catalin pointed in this old thread.
>
>> That's why I propose that this patch set do not depend on the
>> introduction of a asm-generic default relaxed variant of read and
>> write. Later when it will be accepted then this new API will be moved
>> in the asm-generic part.
>
> Indeed, we can't make this generic until we've resolved the issues I mention
> above. I'll start a new thread around that once I've put my thoughts
> together, but that needn't block this patch imo.
I will definitely have a look on this thread!
>
> That said, I'd still suggest resending a final version of this patch, since
> there were some minor issues with this iteration.
Yes sure, I suspect that Ezequiel already fixed all the issues and is ready
to send a new iteration.
>
> Cheers,
>
> Will
>
--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
next prev parent reply other threads:[~2013-09-05 9:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-23 10:24 [PATCH v3 0/3] Introduce atomic MMIO register modify Ezequiel Garcia
2013-08-23 10:24 ` [PATCH v3 1/3] ARM: Introduce atomic MMIO modify Ezequiel Garcia
2013-08-23 10:38 ` Baruch Siach
2013-08-23 11:07 ` Ezequiel Garcia
2013-08-23 11:32 ` Ezequiel Garcia
2013-08-23 11:48 ` Catalin Marinas
2013-08-30 9:08 ` Will Deacon
2013-08-30 9:15 ` Catalin Marinas
2013-08-30 9:20 ` Will Deacon
2013-08-30 10:03 ` Catalin Marinas
2013-08-30 20:08 ` Jason Gunthorpe
2013-08-30 22:18 ` Russell King - ARM Linux
2013-09-05 8:59 ` Gregory CLEMENT
2013-09-05 9:08 ` Will Deacon
2013-09-05 9:20 ` Gregory CLEMENT [this message]
2013-09-06 16:48 ` Jason Gunthorpe
2013-08-23 11:28 ` Ezequiel Garcia
2013-08-23 10:24 ` [PATCH v3 2/3] clocksource: orion: Use atomic access for shared registers Ezequiel Garcia
2013-08-23 10:38 ` Baruch Siach
2013-08-23 10:49 ` Ezequiel Garcia
2013-08-23 10:24 ` [PATCH v3 3/3] watchdog: " Ezequiel Garcia
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