linux-kernel - Re: [PATCHv1] rtc: bcm-iproc: Add support for Broadcom iproc rtc

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Message-ID: <5490A9FC.6030305@broadcom.com>
Date:	Tue, 16 Dec 2014 13:54:04 -0800
From:	Arun Ramamurthy <arun.ramamurthy@...adcom.com>
To:	Ray Jui <rjui@...adcom.com>, Arnd Bergmann <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>
CC:	<mark.rutland@....com>, <a.zummo@...ertech.it>,
	<sbranden@...adcom.com>, <pawel.moll@....com>,
	<devicetree@...r.kernel.org>, <ijc+devicetree@...lion.org.uk>,
	Arun Ramamurthy <arunrama@...adcom.com>,
	<linux-kernel@...r.kernel.org>, <grant.likely@...aro.org>,
	<robh+dt@...nel.org>, <bcm-kernel-feedback-list@...adcom.com>,
	<galak@...eaurora.org>, <rtc-linux@...glegroups.com>
Subject: Re: [PATCHv1] rtc: bcm-iproc: Add support for Broadcom iproc rtc



On 14-12-16 12:27 PM, Ray Jui wrote:
>
>
> On 12/16/2014 12:19 PM, Arnd Bergmann wrote:
>> On Tuesday 16 December 2014 12:05:08 Arun Ramamurthy wrote:
>>> On 14-12-16 11:42 AM, Arnd Bergmann wrote:
>>>> On Tuesday 16 December 2014 11:22:30 arun.ramamurthy@...adcom.com
>>>> wrote:
>>>>> +       rtc: iproc_rtc@...3026000 {
>>>>> +               compatible = "brcm,iproc-rtc";
>>>>> +               reg =   spru_bbl:               <0x03026000 0xC>,
>>>>> +                       crmu_pwr_good_status:   <0x0301C02C 0x14>,
>>>>> +                       crmu_bbl_auth:          <0x03024C74 0x8>;
>>>>> +               interrupts = spru_rtc_periodic: <GIC_SPI 142
>>>>> IRQ_TYPE_LEVEL_HIGH>,
>>>>> +                            spru_alarm:        <GIC_SPI 133
>>>>> IRQ_TYPE_LEVEL_HIGH>;
>>>>
>>>> The reg properties look really random, could it be that the registers
>>>> are really part of some other device that contains multiple functions?
>>>>
>>> This RTC block is on a battery backed logic island and is accessed
>>> indirectly using the spru_bbl registers. The CRMU registers are required
>>> to read the power status and write to some authentication registers.
>>> Without writing to these authentication
>>> registers, we cannot access any of the spru_bbl registers. In conclusion
>>> I don't think the CRMU register accesses can be considered as another
>>> device access. Do you agree Arnd?
>>
>> It sounds like CRMU is some other unit aside from the RTC. Could this
>> be something like a generic system controller? I think it should
>> either have its own driver or use the syscon logic if that is what
>> this is.
>>
> Giving that CRMU has scattered, miscellaneous control logic for multiple
> different peripherals, it probably makes more sense to use the syscon
> logic here.
>
Arnd, thanks for the feedback. If I was to write a separate driver for 
the CRMU, I would have to export certain functions and create an api 
that only this RTC driver would use. I am not sure that is efficient or 
required. What is your opinion?
Would it be better if I use the syson api in my current driver and move 
the CRMU registers to separate syscon device tree entry?

>>>> Also, what do you use the labels for?
>>>>
>>> The labels are purely to improve readability of the device tree entry
>>
>> Please remove them then, they don't help at all.
>>
Sure, I will remove the labels
>>     Arnd
>>
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