linux-kernel - Re: [PATCH 2/6] regulator: anatop: only set supply regulator when it actually exists

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Date:   Thu, 13 Apr 2017 15:11:01 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Dong Aisheng <aisheng.dong@....com>, linux-kernel@...r.kernel.org,
        shawnguo@...nel.org, linux-arm-kernel@...ts.infradead.org,
        kernel@...gutronix.de, lgirdwood@...il.com, yibin.gong@....com
Subject: Re: [PATCH 2/6] regulator: anatop: only set supply regulator when it
 actually exists

Hi Mark,

On Tue, Apr 11, 2017 at 09:31:24PM +0100, Mark Brown wrote:
> On Wed, Apr 12, 2017 at 09:58:43AM +0800, Dong Aisheng wrote:
> > Mandatorily set the initdata->supply_regulator while it actually not
> > exist will cause regulator core to resolve supply each time whenever
> > a new regulator registered which is meaningless and waste CPU mips.
> > 
> > We can observe more than one hundred times of iteration of resolving
> > during a MX6Q SDB board booting up.
> > 
> > This patch adds the condition check for vin-supply to avoid the issue.
> 
> This is an obvious abstraction failure - there is nothing magical about
> your driver which means that we need special casing in it to handle
> badly written DTs that don't specify supplies.  Exactly the same
> argument applies to all other regulators so if this is worth fixing it's
> worth fixing in the core so we substitute in a dummy regulator if the
> supply is genuinely missing.  Which is something we in fact have code to
> do already though for some reason I can't see we bypass it, I'll send a
> patch just now...

You're absolutely right!
I did this because there're some where else did the same thing.
e.g. drivers/regulator/fixed.c.

But it's obviously none of any platform specific and is perfectly
to be handled in regulator core.

Regards
Dong Aisheng