linux-kernel - Re: [PATCH/RFC v9 08/19] leds: Add driver for AAT1290 current regulator

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Message-ID: <20141211155222.GU15559@valkosipuli.retiisi.org.uk>
Date:	Thu, 11 Dec 2014 17:52:22 +0200
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:	linux-leds@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	b.zolnierkie@...sung.com, pavel@....cz, cooloney@...il.com,
	rpurdie@...ys.net, s.nawrocki@...sung.com, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org
Subject: Re: [PATCH/RFC v9 08/19] leds: Add driver for AAT1290 current
 regulator

Hi Jacek,

On Thu, Dec 11, 2014 at 04:34:45PM +0100, Jacek Anaszewski wrote:
> >>+
> >>+	/* write address */
> >>+	for (i = 0; i < addr; ++i) {
> >>+		udelay(AAT1290_EN_SET_TICK_TIME_US);
> >>+		gpio_set_value(led->en_set_gpio, 0);
> >>+		udelay(AAT1290_EN_SET_TICK_TIME_US);
> >>+		gpio_set_value(led->en_set_gpio, 1);
> >>+	}
> >
> >This is a very interesting approach to bus implementation. It's a bit like
> >pulse dial on POTS. :-)
> >
> >>+
> >>+	udelay(AAT1290_LATCH_TIME_US);
> >
> >How precise does this need to be? Could you use usleep_range() instead?
> 
> This is minimal required time, so usleep_range could be used here,
> which would however make the delay of setting the torch brightness
> even more unstable.

True as well. Half a ms isn't that long but then again torch typically isn't
time critical either. I'd use usleep_range(), up to you.

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk
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