linux-kernel - Re: [PATCH 1/4] rtc: sa1100: enable/disable rtc when probe/remove the device

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Message-ID: <CAN1soZwppuRm9ETq1dwhy7Y+_aoJ9Kt5O1rypqD9T6f4caGV6g@mail.gmail.com>
Date:	Mon, 3 Dec 2012 13:35:38 +0800
From:	Haojian Zhuang <haojian.zhuang@...il.com>
To:	Chao Xie <xiechao.mail@...il.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Chao Xie <chao.xie@...vell.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/4] rtc: sa1100: enable/disable rtc when probe/remove the device

On Mon, Dec 3, 2012 at 10:53 AM, Chao Xie <xiechao.mail@...il.com> wrote:
> On Mon, Dec 3, 2012 at 9:39 AM, Chao Xie <xiechao.mail@...il.com> wrote:
>> On Fri, Nov 30, 2012 at 3:04 PM, Haojian Zhuang
>> <haojian.zhuang@...il.com> wrote:
>>> On Thu, Nov 29, 2012 at 6:25 PM, Russell King - ARM Linux
>>> <linux@....linux.org.uk> wrote:
>>>> On Wed, Nov 28, 2012 at 09:21:07PM -0500, Chao Xie wrote:
>>>>> The original sa1100_rtc_open/sa1100_rtc_release will be called
>>>>> when the /dev/rtc0 is opened or closed.
>>>>> In fact, these two functions will enable/disable the clock, and
>>>>> register/unregister the irqs.
>>>>> User application will use /dev/rtc0 to read the rtc time or set
>>>>> the alarm. The rtc should still run indepent of open/close the
>>>>> rtc device.
>>>>> So only enable clock and register the irqs when probe the device,
>>>>> and disable clock and unregister the irqs when remove the device.
>>>>
>>>> NAK.  I don't think you properly understand what's going on here if you
>>>> think moving the entire open and release functions into the probe and
>>>> remove functions is the right thing to do.
>>>
>>> Since PXA27x & PXA3xx supports dual rtc device at the same time,
>>> user could choose use either of rtc at run time. Then clk & irq are setup
>>> in open().
>>>
>>> Chao,
>>> So you shouldn't remove them into probe().
>>
>> How can user to choose one RTC?
>> The user API, for example "date" will open the device, get the time
>> and then close the device.
>> WHen set a alarm, it is the same routine. open->set->close.
>> The open routine will enable clock and register irq, close will
>> disable the clock and unregister irq. It means that if only open is
>> invoked, rtc begins to work, and after close is invoked rtc stops
>> working. It means that the user can not get correct time and can not
>> get right alarm.
>
> hi
> I want to correct what i said. For the irq register/unregister i think
> can be done at open/release. But for clock enable/disable, i do not
> think so. If clock is disabled, as i think RTC will not work. User API
> still use open->get_time->close for "date" command. It means that RTC
> will not return correct date to user.

I didn't get your point. Do you mean that RTC can't work without your patch?
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