From: broonie@opensource.wolfsonmicro.com (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 1/2] mfd: Add anatop mfd driver
Date: Thu, 1 Mar 2012 11:30:32 +0000 [thread overview]
Message-ID: <20120301113031.GD3124@opensource.wolfsonmicro.com> (raw)
In-Reply-To: <1330593052-15184-1-git-send-email-paul.liu@linaro.org>
On Thu, Mar 01, 2012 at 05:10:51PM +0800, Ying-Chun Liu (PaulLiu) wrote:
> + spin_lock(&adata->reglock);
> + val = readl(adata->ioreg + addr);
> + spin_unlock(&adata->reglock);
Do you really need to take a lock for a single read operation from a
memory mapped register? I'd expect this to be atomic in itself. You
need to lock on read/modify/write cycles to make sure that you don't get
a read/read/modify/modify/write/write and misplace one of the modifies
but that's not an issue for an isolated read.
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WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie@opensource.wolfsonmicro.com>
To: "Ying-Chun Liu (PaulLiu)" <paul.liu@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org,
patches@linaro.org, Samuel Ortiz <sameo@linux.intel.com>,
Shawn Guo <shawn.guo@linaro.org>
Subject: Re: [PATCH v5 1/2] mfd: Add anatop mfd driver
Date: Thu, 1 Mar 2012 11:30:32 +0000 [thread overview]
Message-ID: <20120301113031.GD3124@opensource.wolfsonmicro.com> (raw)
In-Reply-To: <1330593052-15184-1-git-send-email-paul.liu@linaro.org>
[-- Attachment #1: Type: text/plain, Size: 508 bytes --]
On Thu, Mar 01, 2012 at 05:10:51PM +0800, Ying-Chun Liu (PaulLiu) wrote:
> + spin_lock(&adata->reglock);
> + val = readl(adata->ioreg + addr);
> + spin_unlock(&adata->reglock);
Do you really need to take a lock for a single read operation from a
memory mapped register? I'd expect this to be atomic in itself. You
need to lock on read/modify/write cycles to make sure that you don't get
a read/read/modify/modify/write/write and misplace one of the modifies
but that's not an issue for an isolated read.
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next prev parent reply other threads:[~2012-03-01 11:30 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-07 13:53 [PATCH] Regulator: Add Anatop regulator driver Ying-Chun Liu (PaulLiu)
2011-12-07 13:53 ` Ying-Chun Liu (PaulLiu)
2011-12-07 15:54 ` Mark Brown
2011-12-07 16:30 ` Ying-Chun Liu (PaulLiu)
2011-12-21 9:03 ` [PATCHv2] " Ying-Chun Liu (PaulLiu)
2011-12-22 11:33 ` Mark Brown
2011-12-24 12:37 ` Mark Brown
2011-12-27 10:06 ` Ying-Chun Liu (PaulLiu)
2011-12-27 10:40 ` Mark Brown
2011-12-27 10:16 ` [PATCH v3] " Ying-Chun Liu (PaulLiu)
2011-12-27 10:52 ` Mark Brown
2011-12-27 11:38 ` Shawn Guo
2012-02-08 20:51 ` [PATCH v4 1/2] mfd: Add anatop mfd driver Ying-Chun Liu (PaulLiu)
2012-02-08 20:51 ` Ying-Chun Liu (PaulLiu)
2012-02-08 20:51 ` [PATCH v4 2/2] Regulator: Add Anatop regulator driver Ying-Chun Liu (PaulLiu)
2012-02-08 20:51 ` Ying-Chun Liu (PaulLiu)
2012-02-09 11:24 ` Mark Brown
2012-02-09 11:24 ` Mark Brown
2012-02-11 6:36 ` Shawn Guo
2012-02-11 6:36 ` Shawn Guo
2012-02-11 13:17 ` Mark Brown
2012-02-11 13:17 ` Mark Brown
2012-02-11 6:05 ` [PATCH v4 1/2] mfd: Add anatop mfd driver Shawn Guo
2012-02-11 6:05 ` Shawn Guo
2012-02-21 11:17 ` Samuel Ortiz
2012-02-21 11:17 ` Samuel Ortiz
2012-03-01 9:19 ` Ying-Chun Liu (PaulLiu)
2012-03-01 9:19 ` Ying-Chun Liu (PaulLiu)
2012-03-01 9:10 ` [PATCH v5 " Ying-Chun Liu (PaulLiu)
2012-03-01 9:10 ` Ying-Chun Liu (PaulLiu)
2012-03-01 9:10 ` [PATCH v5 2/2] Regulator: Add Anatop regulator driver Ying-Chun Liu (PaulLiu)
2012-03-01 9:10 ` Ying-Chun Liu (PaulLiu)
2012-03-01 11:17 ` Mark Brown
2012-03-01 11:17 ` Mark Brown
2012-03-01 11:30 ` Mark Brown [this message]
2012-03-01 11:30 ` [PATCH v5 1/2] mfd: Add anatop mfd driver Mark Brown
2012-03-02 7:00 ` [PATCH v6 " Ying-Chun Liu (PaulLiu)
2012-03-02 7:00 ` Ying-Chun Liu (PaulLiu)
2012-03-02 7:00 ` [PATCH v6 2/2] Regulator: Add Anatop regulator driver Ying-Chun Liu (PaulLiu)
2012-03-02 7:00 ` Ying-Chun Liu (PaulLiu)
2012-03-04 6:51 ` Shawn Guo
2012-03-04 6:51 ` Shawn Guo
2012-03-04 13:29 ` Mark Brown
2012-03-04 13:29 ` Mark Brown
2012-03-02 7:07 ` [PATCH v6 1/2] mfd: Add anatop mfd driver Venu Byravarasu
2012-03-02 7:07 ` Venu Byravarasu
2012-03-02 7:51 ` Ying-Chun Liu (PaulLiu)
2012-03-02 7:51 ` Ying-Chun Liu (PaulLiu)
2012-03-02 8:02 ` Venu Byravarasu
2012-03-02 8:02 ` Venu Byravarasu
2012-03-02 14:00 ` Peter Korsgaard
2012-03-02 14:00 ` Peter Korsgaard
2012-03-03 17:39 ` [PATCH v7 " Ying-Chun Liu (PaulLiu)
2012-03-03 17:39 ` Ying-Chun Liu (PaulLiu)
2012-03-03 17:58 ` Mark Brown
2012-03-03 17:58 ` Mark Brown
2012-03-04 5:25 ` Shawn Guo
2012-03-04 5:25 ` Shawn Guo
2012-03-04 5:42 ` Shawn Guo
2012-03-04 5:42 ` Shawn Guo
2012-03-04 5:55 ` Shawn Guo
2012-03-04 5:55 ` Shawn Guo
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