linux-kernel - Re: [PATCH 1/2] power: reset: at91: add sama5d3 reset function

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Message-ID: <55ACB2C9.5070701@atmel.com>
Date:	Mon, 20 Jul 2015 16:35:21 +0800
From:	Josh Wu <josh.wu@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	<linux-kernel@...r.kernel.org>,
	"Krzysztof Kozlowski" <k.kozlowski.k@...il.com>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Fabian Frederick <fabf@...net.be>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/2] power: reset: at91: add sama5d3 reset function

Hi, Maxime

On 7/20/2015 3:52 PM, Maxime Ripard wrote:
> Hi Josh,
>
> On Mon, Jul 13, 2015 at 11:21:44AM +0800, Josh Wu wrote:
>> On 7/11/2015 12:12 AM, Nicolas Ferre wrote:
>>> Le 10/07/2015 14:31, Maxime Ripard a écrit :
>>>> On Fri, Jul 10, 2015 at 02:09:07PM +0200, Alexandre Belloni wrote:
>>>>> Hi,
>>>>>
>>>>> On 10/07/2015 at 15:56:52 +0800, Josh Wu wrote :
>>>>>> I would agree with Maxime. Currently all latest chip reset function is
>>>>>> compatible with the atmel,sama5d3-rstc.
>>>>>> So check compatible string is enough for now.
>>>>>> But of cause if we have other incompatible reset in future with new chip,
>>>>>> the structure like you said is needed.
>>>>> We managed to avoid using of_machine_is_compatible() in all the at91
>>>>> drivers. I'd like to keep it that way. It was painful enough to remove
>>>>> all those cpu_is_at91xxx calls.
>>>> That's your call...
>>>>
>>>>> Also, using it is trying to match strings and will result in longer boot
>>>>> times.
>>>> Have you looked at the implementation of of_match_device? If that's
>>>> really a concern to you, you should actually avoid it.
>>> I agree: let's keep it simple and use of_match_device().
>> Ok. I will keep it as it is now:  use the (match->data != sama5d3_restart)
>> for the condition.
> I'm not just that's been an option in our discussion so far.
>
> Nicolas said that he was agreeing with me, but at the same time said
> the complete opposite of what I was arguing for, so I'm not really
> sure what's really on his mind, but the two options that were
> discussed were to remove that test, and either:
>
>    - Use of_device_is_compatible to prevent the loop execution

Thank you for explaining, it is clear to me.

I'll take this above option. As the of_device_is_compatible() almost 
same as of_match_node()/of_match_device(). Except that 
of_device_is_compatible() is more efficient (in this case It calls 
__of_device_is_compatible() directly) than of_match_node/of_match_device.

>
>    - define a structure with a flag to say whether you need the ram
>      controller quirk or not, and test that flag.
>
> Maxime
>

Best Regards,
Josh Wu
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