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

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Message-ID: <ffafc50e-9adb-9d66-3d1f-4ebc9f91f47d@ti.com>
Date:   Tue, 10 May 2022 22:47:59 +0530
From:   "J, KEERTHY" <j-keerthy@...com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, <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 5/10/2022 8:55 PM, Daniel Lezcano wrote:
> 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?

Hi Daniel,

Patch 1 & 4 i.e Documentation patch and driver patch can be picked by 
you. I believe Vignesh will take the dts patches.

Vignesh,

Can you confirm?

- Keerthy

> 
>