linux-kernel - Re: [RFC PATCH v3 2/2] drivers: mfd: vexpress: add Serial Power Controller (SPC) support

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Date:	Thu, 13 Jun 2013 20:21:29 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Olof Johansson <olof@...om.net>
cc:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org,
	Jon Medhurst <tixy@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pawel Moll <pawel.moll@....com>,
	Achin Gupta <achin.gupta@....com>,
	Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [RFC PATCH v3 2/2] drivers: mfd: vexpress: add Serial Power
 Controller (SPC) support

On Thu, 13 Jun 2013, Olof Johansson wrote:

> > +	u32 status = readl_relaxed(info->baseaddr + PWC_STATUS);
> 
> Why readl_relaxed() here? Can't you use a normal readl()?

Unfortunately, on ARM readl_relaxed() _is_ the normal readl() because 
the actual readl() may have side effects.  See commit 79f64dbf68c8.


Nicolas
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