linux-kernel - Re: [PATCH v6 4/4] thermal: k3_j72xx_bandgap: Add the bandgap driver support

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Date:   Tue, 10 May 2022 17:25:24 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "J, KEERTHY" <j-keerthy@...com>, robh+dt@...nel.org,
        rui.zhang@...el.com, amitk@...nel.org, kristo@...nel.org,
        vigneshr@...com, krzysztof.kozlowski@...aro.org
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/4] thermal: k3_j72xx_bandgap: Add the bandgap driver
 support

On 09/05/2022 05:10, J, KEERTHY wrote:
> 
> 
> On 4/27/2022 12:16 PM, Keerthy wrote:
>> Add VTM thermal support. In the Voltage Thermal Management
>> Module(VTM), K3 J72XX supplies a voltage reference and a temperature
>> sensor feature that are gathered in the band gap voltage and
>> temperature sensor (VBGAPTS) module. The band gap provides current and
>> voltage reference for its internal circuits and other analog IP
>> blocks. The analog-to-digital converter (ADC) produces an output value
>> that is proportional to the silicon temperature.
>>
>> Currently reading temperatures only is supported.  There are no
>> active/passive cooling agent supported.
>>
>> J721e SoCs have errata i2128: https://www.ti.com/lit/pdf/sprz455
>>
>> The VTM Temperature Monitors (TEMPSENSORs) are trimmed during production,
>> with the resulting values stored in software-readable registers. Software
>> should use these  register values when translating the Temperature
>> Monitor output codes to temperature values.
>>
>> It has an involved workaround. Software needs to read the error codes for
>> -40C, 30C, 125C from the efuse for each device & derive a new look up 
>> table
>> for adc to temperature conversion. Involved calculating slopes & 
>> constants
>> using 3 different straight line equations with adc refernce codes as the
>> y-axis & error codes in the x-axis.
>>
>> -40C to 30C
>> 30C to 125C
>> 125C to 150C
>>
>> With the above 2 line equations we derive the full look-up table to
>> workaround the errata i2128 for j721e SoC.
> 
> Hi Daniel,
> 
> Any feedback on this series? Let me know.

There are a few but that would be nit picking and I don't want to 
postpone this driver any longer.

How do you want to proceed? Shall I take it through my tree?


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