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Subject: Re: [PATCH v2 16/16] hwmon: (mr75203) add debugfs to read and write
 temperature coefficients
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Date:   Mon, 22 Aug 2022 16:59:43 +0300
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To:     Guenter Roeck <linux@roeck-us.net>
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>,
        "Farber, Eliav" <farbere@amazon.com>
References: <20220817054321.6519-1-farbere@amazon.com>
 <20220817054321.6519-17-farbere@amazon.com>
 <20220818231106.GA3505191@roeck-us.net>
From:   "Farber, Eliav" <farbere@amazon.com>
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On 8/19/2022 2:11 AM, Guenter Roeck wrote:
> On Wed, Aug 17, 2022 at 05:43:21AM +0000, Eliav Farber wrote:
>> This change adds debugfs to read and write TS coefficients - g, h, j and
>> cal5.
>>
>> The coefficients can vary between product and product, so to calibrate
>> them it can be very useful to to be able to modify them on the fly.
>>
>> e.g.
>>
>> cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
>> 4096
>>
>> echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g
>>
>
> What happens if you write 0 into all those attributes, or 0xffffffff ?
The driver equation is:
T = G + H * (n / cal5 - 0.5) + J * F
So I added protection for cal5 not being 0.
Besides that there is no limitation on what these values can be.
I can't really think of any other logical limitation I can apply.

--
Regards, Eliav