From: Guenter Roeck <linux@roeck-us.net>
To: "Farber, Eliav" <farbere@amazon.com>
Cc: jdelvare@suse.com, robh+dt@kernel.org, mark.rutland@arm.com,
linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, talel@amazon.com,
hhhawa@amazon.com, jonnyc@amazon.com, hanochu@amazon.com,
ronenk@amazon.com, itamark@amazon.com, shellykz@amazon.com,
shorer@amazon.com, amitlavi@amazon.com, almogbs@amazon.com,
dwmw@amazon.co.uk, rtanwar@maxlinear.com
Subject: Re: [PATCH v2 12/16] hwmon: (mr75203) modify the temperature equation
Date: Fri, 19 Aug 2022 04:35:48 -0700 [thread overview]
Message-ID: <20220819113548.GB3106213@roeck-us.net> (raw)
In-Reply-To: <2cc79934-2280-79e6-6e63-0e3eb7107e1c@amazon.com>
On Fri, Aug 19, 2022 at 10:44:06AM +0300, Farber, Eliav wrote:
> On 8/18/2022 11:23 PM, Guenter Roeck wrote:
> > On Wed, Aug 17, 2022 at 05:43:17AM +0000, Eliav Farber wrote:
> > > Modify the equation and coefficients to convert the digital output to
> > > temperature according to series 5 of the Moortec Embedded Temperature
> > > Sensor (METS) datasheet:
> > > T = G + H * (n / cal5 - 0.5) + J * F
> > >
> > > The G, H and J coefficients are multiplied by 1000 to get the
> > > temperature
> > > in milli-Celsius.
> > >
> >
> > This is, at the very least, confusing. It doesn't explain the discrepancy
> > to the old code nor the change in constant values. I have no idea if this
> > change would result in erroneous readings on some other system where
> > the existing calculation may be the correct one.
>
> When I tested the driver it was also not clear to me why the equation
> and coefficients in the code don't match the specifications in the data
> sheet.
> I reached out to Maxlinear engineers (@rtanwar) and they also couldn't
> explain the discrepancy.
> After further correspondence I aligned both the equation and coefficients
> in the driver code to the equation and coefficients defined in series 5
> of the Moortec Embedded Temperature Sensor (METS) datasheet which they
> provided.
>
At least some of the discrepancy is because the original code is more
optimized and avoids overflow. Either case, the above needs to be explained
in the commit description.
> > On top of that, it seems overflow-prune in 32 bit systems.
>
> I'll check if it can overflow, and if it can I'll fix in next version.
>
> --
> Regards, Eliav
>
next prev parent reply other threads:[~2022-08-19 11:35 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-17 5:43 [PATCH v2 00/16] Variety of fixes and new features for mr75203 driver Eliav Farber
2022-08-17 5:43 ` [PATCH v2 01/16] hwmon: (mr75203) fix VM sensor allocation when "intel,vm-map" not defined Eliav Farber
2022-08-18 19:40 ` Guenter Roeck
2022-08-18 20:01 ` [PATCH v2 01/16] hwmon: (mr75203) fix VM sensor allocation when "intel, vm-map" " Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 02/16] hwmon: (mr75203) update pvt->v_num to the actual number of used sensors Eliav Farber
2022-08-18 19:44 ` Guenter Roeck
2022-08-17 5:43 ` [PATCH v2 03/16] hwmon: (mr75203) update Moortec PVT controller intel,vm-map property Eliav Farber
2022-08-18 19:47 ` Guenter Roeck
2022-08-18 20:20 ` [PATCH v2 03/16] hwmon: (mr75203) update Moortec PVT controller intel, vm-map property Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 04/16] hwmon: (mr75203) add Moortec PVT controller reset-control-skip property Eliav Farber
2022-08-18 20:01 ` Guenter Roeck
2022-08-22 11:54 ` Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 05/16] hwmon: (mr75203) add option to skip reset controller Eliav Farber
2022-08-17 5:43 ` [PATCH v2 06/16] hwmon: (mr75203) fix multi-channel voltage reading Eliav Farber
2022-08-18 20:03 ` Guenter Roeck
2022-08-22 12:37 ` Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 07/16] hwmon: (mr75203) add VM active channels property for Moortec PVT controller Eliav Farber
2022-08-18 20:07 ` Guenter Roeck
2022-08-17 5:43 ` [PATCH v2 08/16] hwmon: (mr75203) add VM active channel support Eliav Farber
2022-08-17 5:43 ` [PATCH v2 09/16] hwmon: (mr75203) add VM pre-scalar property for Moortec PVT controller Eliav Farber
2022-08-18 20:11 ` Guenter Roeck
2022-08-19 7:13 ` Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 10/16] hwmon: (mr75203) add VM pre-scalar support Eliav Farber
2022-08-17 5:43 ` [PATCH v2 11/16] hwmon: (mr75203) add protection for negative voltage value Eliav Farber
2022-08-18 20:13 ` Guenter Roeck
2022-08-17 5:43 ` [PATCH v2 12/16] hwmon: (mr75203) modify the temperature equation Eliav Farber
2022-08-18 20:23 ` Guenter Roeck
2022-08-19 7:44 ` Farber, Eliav
2022-08-19 11:35 ` Guenter Roeck [this message]
2022-08-17 5:43 ` [PATCH v2 13/16] hwmon: (mr75203) add thermal coefficient properties for Moortec PVT controller Eliav Farber
2022-08-18 20:25 ` Guenter Roeck
2022-08-22 13:24 ` Farber, Eliav
2022-08-22 16:25 ` Guenter Roeck
2022-08-29 18:46 ` Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 14/16] hwmon: (mr75203) parse thermal coefficients from device-tree Eliav Farber
2022-08-18 20:28 ` Guenter Roeck
2022-08-19 7:57 ` Farber, Eliav
2022-08-19 11:36 ` Guenter Roeck
2022-08-19 11:38 ` Guenter Roeck
2022-08-22 13:41 ` Farber, Eliav
2022-08-22 16:31 ` Guenter Roeck
2022-08-29 18:59 ` Farber, Eliav
2022-08-17 5:43 ` [PATCH v2 15/16] hwmon: (mr75203) fix coding style space errors Eliav Farber
2022-08-17 5:43 ` [PATCH v2 16/16] hwmon: (mr75203) add debugfs to read and write temperature coefficients Eliav Farber
2022-08-18 23:11 ` Guenter Roeck
2022-08-22 13:59 ` Farber, Eliav
2022-08-22 16:28 ` Guenter Roeck
2022-08-29 18:41 ` Farber, Eliav
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