linux-kernel - Re: [PATCH v3 5/5] hisilicon/dts: Add hi655x pmic dts node

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Date:	Mon, 21 Dec 2015 14:20:16 +0800
From:	chenfeng <puck.chen@...ilicon.com>
To:	Mark Brown <broonie@...nel.org>
CC:	<lee.jones@...aro.org>, <linux-kernel@...r.kernel.org>,
	<lgirdwood@...il.com>, <robh+dt@...nel.org>, <pawel.moll@....com>,
	<mark.rutland@....com>, <ijc+devicetree@...lion.org.uk>,
	<galak@...eaurora.org>, <xuwei5@...ilicon.com>,
	<puck.chen@...yun.com>, <yudongbin@...ilicon.com>,
	<saberlily.xia@...ilicon.com>, <suzhuangluan@...ilicon.com>,
	<kong.kongxinwei@...ilicon.com>, <xuyiping@...ilicon.com>,
	<z.liuxinliang@...ilicon.com>, <weidong2@...ilicon.com>,
	<w.f@...wei.com>, <qijiwen@...ilicon.com>,
	<peter.panshilin@...ilicon.com>, <dan.zhao@...ilicon.com>,
	<linuxarm@...wei.com>
Subject: Re: [PATCH v3 5/5] hisilicon/dts: Add hi655x pmic dts node



On 2015/12/21 11:01, chenfeng wrote:
> Mark,
> 
> On 2015/12/19 1:58, Mark Brown wrote:
>> On Thu, Dec 17, 2015 at 11:27:27AM +0800, chenfeng wrote:
>>
>>>  +- regulator-vset-regs: Voltage set register offset.
>>>  +- regulator-vset-mask: voltage set control mask.
>>>  +- regulator-n-vol: The num of support voltages.
>>>  +- regulator-vset-table: The table of support voltages.
>>
>>>> Why is this in the binding?  This is a binding for a specific device,
>>>> there is no point in putting all these data tables in the DT - it just
>>>> bloats the DT and makes it harder for us to enhance our support for this
>>>> device in the future.
>>
>>> You mentioned in previous version,I I have some questions for it.
>>
>>> This regulator-vset-regs etc are vendor specific describe. The hi655x PMIC
>>
>> There's nothing vendor specific about the way this is written...
>>
>>> is a series of chips. They all have this value, but the offset may be different.
>>> And we can generate the dts file from excel which is defined by SOC.
>>
>>> I think the dts is designed to distinguish different platform. If we hard code this
>>> in files, it may be also different to use as common in next chip version.
>>
>> If your tooling can generate DT files it can generate C code just as
>> well and it seems unlikely you're going to be able to build new boards
>> without being able to do firmware updates here.  Especially for the
>> sorts of systems that use DT the set of scenarios where you're able to
>> update the DT but not the kernel seems like it will be extremely
>> limited.  I don't really buy the argument that there's any practical
>> difference in the ability to update the kernel and DT and to the extent
>> there is one it seems better to keep the ABI we have to support smaller
>> by having the DT be minimal.
>>
>> This also allows us to map things more efficiently than we can with just
>> a table of voltages.  For example a good selection of the regulators in
>> your example DT appear to be linear ranges and so should be mapped as
>> such so we can do direct calcuations rather than having to iterate
>> through a table to map voltages into selectors.  That gets especially
>> serious for higher resolution regulators like most DCDCs (and modern
>> LDOs for that matter).
>>
> Thanks,
> I see, I will change the table of voltages into driver.
> like this,
> static const unsigned int voltages[] = {
> 	1500000, 1800000, 2400000, 2500000,
> 	2600000, 2700000, 2850000, 3000000,
> };
> 
> And there will be two open-code function for is-enable and disable in the regulator driver.
> Since we need use the status and disable register on PM chip. Only enable reg in the regulator desc.
> 
> Do you agree with this?
> 
While doing this in driver code, I found that it seems all the vendor chip have
the voltage table. So I am wondering can we add this into the regulator framework.

We can add in the function of_get_regulation_constraints to get the vset table.

I am not sure this is right or not.
> 
> 

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