linux-kernel - Re: [PATCH v2 1/2] dt-bindings: hwmon: Add lltc ltc4286 driver bindings

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Message-ID: <708e84f3-01ac-455e-9b66-2f0e2be1a874@roeck-us.net>
Date:   Tue, 31 Oct 2023 07:14:54 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Delphine_CC_Chiu/WYHQ/Wiwynn <Delphine_CC_Chiu@...ynn.com>,
        Conor Dooley <conor@...nel.org>
Cc:     "patrick@...cx.xyz" <patrick@...cx.xyz>,
        Jean Delvare <jdelvare@...e.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: hwmon: Add lltc ltc4286 driver
 bindings

On 10/30/23 23:25, Delphine_CC_Chiu/WYHQ/Wiwynn wrote:
[ ... ]
>>
>> Actually, turns out there is some contradiction in the LTC4286 datasheet.
>> It mentions different coefficients in different places. It is all but impossible to
>> determine if the datasheet is wrong or if the chip uses a variety of coefficients
>> unless one has a real chip available. Sigh :-(.
> We are not the chip vendor, but we could forward your question to vendor.
> Could you point out the exact places (which pages) where are the contradiction in LTC4286 datasheet?
> 

See "PMBUS COMMAND SUMMARY", default values:

"IOUT_OC_WARN_LIMIT" says "21.3 mV/RSENSE"

"PIN_OP_WARN_LIMIT" says "2.8/RSENSE"

This seems to contradict "Table 8. PMBus M, B, and R Parameters". But then,
reading it again (and again), I think it is just an odd and confusing way
of trying to describe the 0x7fff default register values. Sorry for the noise.

Guenter