linux-kernel - Re: [PATCH 6/6] regulator: anatop: set default voltage selector for pcie

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Date:   Thu, 13 Apr 2017 00:11:35 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Dong Aisheng <aisheng.dong@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Liam Girdwood <lgirdwood@...il.com>, yibin.gong@....com,
        Richard Zhu <hongxing.zhu@....com>
Subject: Re: [PATCH 6/6] regulator: anatop: set default voltage selector for pcie

On Wed, Apr 12, 2017 at 11:49 PM, Mark Brown <broonie@...nel.org> wrote:
> On Thu, Apr 13, 2017 at 03:41:03PM +0800, Dong Aisheng wrote:
>> On Tue, Apr 11, 2017 at 09:40:03PM +0100, Mark Brown wrote:
>
>> > Why is this the only anatop regulator which can have this problem and
>> > how do we know this is a good value?
>
>> Anatop regulator has no separate gate bit.
>> e.g.
>> 00000 Power gated off
>> 00001 Target core voltage = 0.725V
>> ...
>> So it may have no valid default voltage in case it's disabled in
>> bootloader.
>> e.g. regulator_enable() may not work.
>
> That doesn't answer my question.  What I'm asking is why another anatop
> regulator might not end up disabled like this one.
>

Well, that's true and i once thought of it.
Currently it is probably a quick fix and we did not see any others up till now
for all MX6&7 platforms based on NXP internal tree.

If we do see it in the future, then probably a better solution is constructing
a staticly defined default voltage table in anatop driver and do dynamically
check.

>> The default voltage 1.100v this patch sets is defined in reference
>> manual.
>
> For the SoC you're currently looking at...  might another have a
> different value?

No, only MX6SX has it currently.

Regards
Dong Aisheng