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

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Date:	Mon, 20 Jul 2015 17:13:13 +0800
From:	Josh Wu <josh.wu@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	<linux-pm@...r.kernel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Krzysztof Kozlowski <k.kozlowski.k@...il.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	<linux-kernel@...r.kernel.org>, Sebastian Reichel <sre@...nel.org>,
	Fabian Frederick <fabf@...net.be>,
	"Wei Yongjun" <yongjun_wei@...ndmicro.com.cn>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 1/2] power: reset: at91: add sama5d3 reset function

On 7/20/2015 4:44 PM, Josh Wu wrote:
> On 7/20/2015 4:35 PM, Josh Wu wrote:
>> 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.
>
> Sorry, after checking the code a little, I'd say use the of_match_node 
> instead of of_device_is_compatible() is better. Since After check the 
> of_device_is_compatible() we also need to call of_match_node() again.

Okay, Please forget above reply. As Maxime said test the pointer is not 
good solution here.
So I'll sent out v2 which use of_device_is_compatible().

Best Regards,
Josh Wu

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