linux-kernel - Re: [Patch v3 0/5] Introduce keystone reset driver

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Date:	Tue, 20 May 2014 09:49:17 -0400
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Arnd Bergmann <arnd@...db.de>,
	Ivan Khoronzhuk <ivan.khoronzhuk@...com>
CC:	<dbaryshkov@...il.com>, <dwmw2@...radead.org>,
	<ijc+devicetree@...lion.org.uk>, <robh+dt@...nel.org>,
	<pawel.moll@....com>, <mark.rutland@....com>,
	<galak@...eaurora.org>, <grant.likely@...aro.org>,
	<rdunlap@...radead.org>, <linux@....linux.org.uk>,
	<grygorii.strashko@...com>, <olof@...om.net>, <w-kwok2@...com>,
	<sboyd@...eaurora.org>, <devicetree@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Patch v3 0/5] Introduce keystone reset driver

On Tuesday 20 May 2014 09:44 AM, Arnd Bergmann wrote:
> On Tuesday 20 May 2014 16:16:08 Ivan Khoronzhuk wrote:
>> Thank for the reply
>>
>> The reset driver uses two ranges:
>> - RSTYPE, RSTCTRL,RSTCFG, RSISO  (Reset Main PLL Controller)
>> - RESETMUX8-10 registers
>>
>> The content of these register ranges are completely used by the reset 
>> driver.
>> Currently no one on the SoC can access them instead of the reset driver.
>> Also we don't use syscon/regmap at all - so adding this will be some 
>> overhead.
>>
>> As I posted previously:
>> "...configuring Reset multiplexer & PLL. And it tunes not only watchdog 
>> usage..."
>>
>> Yes, it tunes not only watchdog usage and uses part of registers from 
>> PLL controller,
>> but all it works with are connected with reset functionality. These 
>> ranges are used only
>> by reset driver and their purpose is reset functionality.
>>
>> Maybe in the future some soft can use ranges in question for own tasks, 
>> but it should be
>> done via reset driver. So as I see there is no reasons to use regmap for 
>> reset driver.
> 
> You should not look at these registers in isolation, they are part of
> some register area that has other functions as well and that you should
> at least represent correctly in DT.
>
> When I see something like
> 
> +                       reg = <0x23100e4 0x10>,
> +                             <0x2620328 0x10>;
> 
> I am certain that there are other things between 0x2310000 and 0x23100e3, and
> probably after 0x23100f4 as well. There must be some data sheet that
> gives this register range a proper name, so put that into DT rather than
> making up some arbitrary stuff that happens to match how today's kernel
> driver needs it.
> 
Even though there are no other users, I think you have a valid point about
DT representing the hardware layout in the correct form.

Regards,
Santosh

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