linux-kernel - Re: [PATCH v6 1/6] gpio: davinci: use readl/writel instead of __raw

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Date:	Tue, 26 Nov 2013 13:59:16 +0530
From:	Prabhakar Lad <prabhakar.csengg@...il.com>
To:	Sekhar Nori <nsekhar@...com>
Cc:	Taras Kondratiuk <taras.kondratiuk@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	DLOS <davinci-linux-open-source@...ux.davincidsp.com>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LDOC <linux-doc@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>
Subject: Re: [PATCH v6 1/6] gpio: davinci: use readl/writel instead of __raw_*

Hi Sekhar,

On Mon, Nov 25, 2013 at 4:04 PM, Sekhar Nori <nsekhar@...com> wrote:
> Prabhakar,
>
> On Monday 25 November 2013 09:42 AM, Prabhakar Lad wrote:
>> Hi Taras,
>>
>> On Fri, Nov 22, 2013 at 3:38 PM, Taras Kondratiuk
>> <taras.kondratiuk@...aro.org> wrote:
>>> On 21 November 2013 20:15, Prabhakar Lad <prabhakar.csengg@...il.com> wrote:
>>>> From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
>>>>
>>>> This patch replaces the __raw_readl/writel with
>>>> readl and writel, Altough the code runs on ARMv5
>>>> based SOCs, changing this will help copying the code
>>>> for other uses.
>>>
>>> This replacement has a functional impact: it adds memory barriers.
>>> Please note this in the description.
>>> Also please add a bit of explanation on why do you need to add barriers.
>>>
>> Agreed this adds memory barriers, I'll add a note about it.
>
> Well the barriers certainly make it easier to debug by having both
> device and memory accesses happen in program order. That said, if there
> is no pressing reason to add barriers, you can use
> {readl|writel}_relaxed() instead. That will make the code protable
> across endianess.
>
OK will use {readl|writel}_relaxed() instead.

Regards,
--Prabhakar Lad
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