From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] ux500: Adding support for u8500 Hsem functionality V2
Date: Tue, 19 Apr 2011 18:10:17 +0200 [thread overview]
Message-ID: <201104191810.18170.arnd@arndb.de> (raw)
In-Reply-To: <4DADB2F1.1080405@linaro.org>
On Tuesday 19 April 2011, Mathieu Poirier wrote:
> > One more thing I just noticed: the hwspinlock_internal.h file defines
> > the hwspinlock->id field as "a global, unique, system-wide, index of
> > the lock", but the u8500 hsem just sets it to an integer starting
> > at zero. If there are multiple devices providing hwspinlocks in the
> > same system, that cannot work.
> >
> I have to admit I'm not sure of what your asking here. Hwspinlocks
> should be administered by only one entity and this is what this driver
> is doing.
>
> Please get back to me with a clarification.
You could have a system with multiple instances of the hardware block
that holds your spinlock. I've seen SMP systems that basically take
multiple SOCs and put them into a common address space.
More importantly, there could be a device on an external bus that also
provides a hwspinlock. The API can deal with this, but your driver will
conflict with any other driver trying to do the same.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org, ohad@wizery.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] ux500: Adding support for u8500 Hsem functionality V2
Date: Tue, 19 Apr 2011 18:10:17 +0200 [thread overview]
Message-ID: <201104191810.18170.arnd@arndb.de> (raw)
In-Reply-To: <4DADB2F1.1080405@linaro.org>
On Tuesday 19 April 2011, Mathieu Poirier wrote:
> > One more thing I just noticed: the hwspinlock_internal.h file defines
> > the hwspinlock->id field as "a global, unique, system-wide, index of
> > the lock", but the u8500 hsem just sets it to an integer starting
> > at zero. If there are multiple devices providing hwspinlocks in the
> > same system, that cannot work.
> >
> I have to admit I'm not sure of what your asking here. Hwspinlocks
> should be administered by only one entity and this is what this driver
> is doing.
>
> Please get back to me with a clarification.
You could have a system with multiple instances of the hardware block
that holds your spinlock. I've seen SMP systems that basically take
multiple SOCs and put them into a common address space.
More importantly, there could be a device on an external bus that also
provides a hwspinlock. The API can deal with this, but your driver will
conflict with any other driver trying to do the same.
Arnd
next prev parent reply other threads:[~2011-04-19 16:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 15:24 [PATCH 1/2] ux500: Adding support for u8500 Hsem functionality V2 mathieu.poirier at linaro.org
2011-04-11 15:24 ` mathieu.poirier
2011-04-12 13:44 ` Ohad Ben-Cohen
2011-04-12 13:44 ` Ohad Ben-Cohen
2011-04-12 16:53 ` Mathieu Poirier
2011-04-12 16:53 ` Mathieu Poirier
2011-04-12 17:46 ` Arnd Bergmann
2011-04-12 17:46 ` Arnd Bergmann
2011-04-12 19:13 ` Mathieu Poirier
2011-04-12 19:13 ` Mathieu Poirier
2011-04-13 8:45 ` Ohad Ben-Cohen
2011-04-13 8:45 ` Ohad Ben-Cohen
2011-04-17 20:39 ` Arnd Bergmann
2011-04-17 20:39 ` Arnd Bergmann
2011-04-19 16:06 ` Mathieu Poirier
2011-04-19 16:06 ` Mathieu Poirier
2011-04-19 16:10 ` Arnd Bergmann [this message]
2011-04-19 16:10 ` Arnd Bergmann
2011-09-05 21:09 ` Ohad Ben-Cohen
2011-09-05 21:09 ` Ohad Ben-Cohen
2011-09-06 7:15 ` Linus Walleij
2011-09-06 7:15 ` Linus Walleij
2011-09-06 7:27 ` Ohad Ben-Cohen
2011-09-06 7:27 ` Ohad Ben-Cohen
2011-04-13 8:16 ` Ohad Ben-Cohen
2011-04-13 8:16 ` Ohad Ben-Cohen
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