linux-kernel - RE: [lm-sensors] [PATCH V1] fix adc to voltage calculation in da9052 power driver

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Message-ID: <24DF37198A1E704D9811D8F72B87EB51847AC44F@NB-EX-MBX02.diasemi.com>
Date:	Thu, 19 Dec 2013 18:15:57 +0000
From:	"Opensource [Anthony Olech]" <anthony.olech.opensource@...semi.com>
To:	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <khali@...ux-fr.org>
CC:	"Opensource [Anthony Olech]" <anthony.olech.opensource@...semi.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	Anton Vorontsov <anton@...msg.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"David Dajun Chen" <david.chen@...semi.com>
Subject: RE: [lm-sensors] [PATCH V1] fix adc to voltage calculation in
 da9052 power driver

> -----Original Message-----
> From: Guenter Roeck [mailto:groeck7@...il.com] On Behalf Of Guenter
> Roeck
> Sent: 19 December 2013 18:11
> To: Jean Delvare
> Cc: Opensource [Anthony Olech]; lm-sensors@...sensors.org; Anton
> Vorontsov; David Woodhouse; linux-kernel@...r.kernel.org; David Dajun
> Chen
> Subject: Re: [lm-sensors] [PATCH V1] fix adc to voltage calculation in da9052
> power driver
> On Thu, Dec 19, 2013 at 03:54:54PM +0100, Jean Delvare wrote:
> > Hi Anthony,
> >
> [ ... ]
> > BTW, you (and we) probably shouldn't waste too much energy on this.
> > ADCs are only accurate to some degree anyway. If you take the
> > components connected to the input into consideration, the accuracy
> > gets even worse. For example, if the input voltage must be scaled down
> > to fit in the ADC's range, you need at least one resistor, which in
> > best cases will have a 1% accurate value (known as tolerance.) That's
> > ten times the LSB of your 10-bit ADC, at which point / 1023 or / 1024
> > really makes no practical difference. Sub-percent tolerant resistors
> > are expensive and rare in consumer electronics in my experience.
> True, but on the other side (and after looking into the datasheet) the driver
> already calculated the voltage on adc4..6 correctly, so unless you disagree I
> would like to apply the hwmon patch to -next for consistency.
> Thanks,
> Guenter

OK, thanks,
Tony Olech
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