linux-kernel - Re: [PATCH V2 05/19] bus: omap_l3_noc: switch over to relaxed variants of readl/writel

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Message-ID: <20140421150919.GE27341@saruman.home>
Date:	Mon, 21 Apr 2014 10:09:19 -0500
From:	Felipe Balbi <balbi@...com>
To:	Nishanth Menon <nm@...com>
CC:	<balbi@...com>, Santosh Shilimkar <santosh.shilimkar@...com>,
	Tony Lindgren <tony@...mide.com>,
	Sricharan R <r.sricharan@...com>, Sekhar Nori <nsekhar@...com>,
	Rajendra Nayak <rnayak@...com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	<devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 05/19] bus: omap_l3_noc: switch over to relaxed
 variants of readl/writel

On Mon, Apr 21, 2014 at 08:16:28AM -0500, Nishanth Menon wrote:
> On 04/17/2014 05:03 PM, Felipe Balbi wrote:
> > On Thu, Apr 17, 2014 at 05:56:15PM -0400, Santosh Shilimkar wrote:
> >> On Thursday 17 April 2014 05:52 PM, Felipe Balbi wrote:
> >>> Hi,
> >>>
> >>> On Thu, Apr 17, 2014 at 03:49:21PM -0500, Nishanth Menon wrote:
> >>>> Currently we use __raw_readl and writel in this driver, however, there
> >>>
> >>> __raw_* and *_relaxed variants are the same, just have a look <asm/io.h>
> >>>
> >> Except the relaxed version can take care of endian conversion if
> >> needed. :-)
> > 
> > right, but according to commit log, this commit is more concerned about
> > the memory barriers which writel()/readl() add, not endianness. Just a
> > matter of fixing up commit log.
> > 
> 
> yep, this patch does replace writel with writel_relaxed there is no
> strong need for barriers in the operations that we perform here.
> 
> I agree that the commit message should probably be a little more
> detailed at this point.
> 
> 
> How about:
> Currently we use __raw_readl and writel in this driver. Considering
> there is no specific need for a memory barrier, replacing writel with
> endian-neutral writel_relaxed and replacing __raw_readls with the
> corresponding endian-neutral readl_relaxed allows us to have a
> standard set of register operations for the driver.
> 
> While at it, simplify address computation using variables for register.

reads a lot better, thanks

Acked-by: Felipe Balbi <balbi@...com>


-- 
balbi

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