linux-kernel - Re: [PATCH 2/2] leds: lm3692x: Allow to set ovp and brigthness mode

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Message-ID: <20191224112616.GA23468@bogon.m.sigxcpu.org>
Date:   Tue, 24 Dec 2019 12:26:16 +0100
From:   Guido Günther <agx@...xcpu.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] leds: lm3692x: Allow to set ovp and brigthness mode

Hi,
On Sat, Dec 21, 2019 at 08:18:44PM +0100, Pavel Machek wrote:
> Hi!
> 
> > Overvoltage protection and brightness mode are currently hardcoded
> > as disabled in the driver. Make these configurable via DT.
> 
> What exactly is overvoltage protection good for? Should we default to
> 29V if we have no other information?

The OVP protects the IC from overvoltage conditions on the output side.
While looking at the manual again I noticed that i misremembered the
'00' value which means 17V - not unprotected. Also the chip defaults
to 29V OVP so i've adjusted that too.

Cheers,
 -- Guido

> 
> > Signed-off-by: Guido Günther <agx@...xcpu.org>
> 
> > +	ret = device_property_read_u32(&led->client->dev,
> > +				       "ti,overvoltage-volts", &ovp);
> > +	if (!ret) {
> > +		switch (ovp) {
> > +		case 0:
> > +			break;
> > +		case 22:
> > +			led->boost_ctrl |= LM3692X_OVP_21V;
> > +			break;
> 
> Should be case 21.
> 								Pavel
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html