linux-kernel - Re: LM90 driver and ti tmp461 detection

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Message-ID: <20151210180314.GB28022@awelinux>
Date:	Thu, 10 Dec 2015 19:03:14 +0100
From:	Andreas Werner <andreas.werner@....de>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Andreas Werner <andreas.werner@....de>,
	<linux-kernel@...r.kernel.org>, <jdelvare@...e.com>,
	<lm-sensors@...sensors.org>, <wni@...dia.com>
Subject: Re: LM90 driver and ti tmp461 detection

...
> On Thu, Dec 10, 2015 at 09:43:53AM -0800, Guenter Roeck wrote:
> >
> >There is one difference. The temperature ranges differ:
> >
> >TMP451:
> >Standard Mode: 0 to +127
> >Extended Mode: -64 to +191
> >
> >TMP461:
> >Standard Mode: -40 to +127
> >Extended Mode: -64 to +191
> >
> >Therefore the calcualtion is different then the tmp451 one.
> >
> Not really. The tmp451 will return 0 for negative temperatures in standard mode,
> the tmp461 will return negative (signed) values. Temperatures are stored
> as signed values, so the code should be ok as is. Am I missing something ?
> 

It will work to read the local and external temperature yes, but not
for setting the temperatur.
If setting in standard mode, the tmp451 part fix the value to 0-127
but for the tmp461 we have -40 to 127.

I'v currently no chip here in the office to test it, hopefully I will
get one next week.

> >I also aggree with you with the magical ID register. I hate such
> >kind of register with are not documented and may have a value.
> >
> >I have a DT based board yes, but i have also planed to submit my changes
> >and also wanted to implement the autodetection of the chip.
> 
> I don't think auto-detection (other than handling the chip as tmp451)
> will be possible, but I am looking forward to seeing your patch(es).
> 

Yes, i think autodetection makes it very crapy. May be i will find
another solution.

> >
> >I have also planned (or need) to implement the "n-Factor Correction" for the
> >CPU diodes. There is a register to set this value in the tmp451 and tmp461.
> >Would that make sense to add a DT property for the driver to be able
> >to set this value? What do you think?
> >
> Yes, since this is a board (hardware) property. Other chips have similar
> registers. We'll just have to find a good set of property names and descriptions.
> 

Ok, I will find a way to do it :-)

> Thanks,
> Guenter
> 

Regards
Andy
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