linux-kernel - Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

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Message-ID: <20130910101359.GX29403@sirena.org.uk>
Date:	Tue, 10 Sep 2013 11:13:59 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Wei Ni <wni@...dia.com>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	"khali@...ux-fr.org" <khali@...ux-fr.org>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

On Tue, Sep 10, 2013 at 01:39:59PM +0800, Wei Ni wrote:

> I think the device need time to wait stable after power on, but it's
> difficult to get an exact delay value, and this delay may also relate
> with platform design, so how about to add a optional property in the DT
> node, such as "power-on-delay-ms" ?

This is something you should *really* be able to get from the datasheet
for the part - this sort of stuff has to be documented for hardware to
be used robustly.  It seems entirely possible that you are working
around an issue with the regulator driver you are using not correctly
providing its ramp time here.

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