linux-kernel - Re: [PATCH v3 2/4] thermal: k3: Add support for bandgap sensors

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Date:   Wed, 19 Feb 2020 18:13:56 +0530
From:   Keerthy <j-keerthy@...com>
To:     Randy Dunlap <rdunlap@...radead.org>, <rui.zhang@...el.com>,
        <robh+dt@...nel.org>, <daniel.lezcano@...aro.org>
CC:     <amit.kucheria@...durent.com>, <t-kristo@...com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
        <mark.rutland@....com>
Subject: Re: [PATCH v3 2/4] thermal: k3: Add support for bandgap sensors



On 19/02/20 1:20 pm, Randy Dunlap wrote:
> On 2/18/20 11:43 PM, Keerthy wrote:
>> The bandgap 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 and trend computing is supported
>> as there are no active/passive cooling agent supported.
>>
>> Signed-off-by: Keerthy <j-keerthy@...com>
>> ---
>>   drivers/thermal/Kconfig      |  12 ++
>>   drivers/thermal/Makefile     |   1 +
>>   drivers/thermal/k3_bandgap.c | 342 +++++++++++++++++++++++++++++++++++
>>   3 files changed, 355 insertions(+)
>>   create mode 100644 drivers/thermal/k3_bandgap.c
>>
>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>> index 5a05db5438d6..fa598eddc7ac 100644
>> --- a/drivers/thermal/Kconfig
>> +++ b/drivers/thermal/Kconfig
>> @@ -251,6 +251,18 @@ config IMX_THERMAL
>>   	  cpufreq is used as the cooling device to throttle CPUs when the
>>   	  passive trip is crossed.
>>   
>> +config K3_THERMAL
>> +	bool "Texas Instruments K3 thermal support"
> 
> Hi,
> Why is this bool and not tristate?

Definitely can work as tristate. I will fix it next version.

> 
>> +	depends on THERMAL
>> +	depends on ARCH_K3 || COMPILE_TEST
>> +	help
>> +	  If you say yes here you get thermal support for the Texas Instruments
>> +	  K3 SoC family. The current chip supported is:
>> +	   - AM654
>> +
>> +	  This includes temperature reading functionality and also trend
>> +	  computation.
>> +
>>   config MAX77620_THERMAL
>>   	tristate "Temperature sensor driver for Maxim MAX77620 PMIC"
>>   	depends on MFD_MAX77620
> 
>> diff --git a/drivers/thermal/k3_bandgap.c b/drivers/thermal/k3_bandgap.c
>> new file mode 100644
>> index 000000000000..35d904eb9857
>> --- /dev/null
>> +++ b/drivers/thermal/k3_bandgap.c
>> @@ -0,0 +1,342 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * TI Bandgap temperature sensor driver for K3 SoC Family
>> + *
>> + * Copyright (C) 2020 Texas Instruments Incorporated - http://www.ti.com/
>> + */
> 
>> +static int k3_bgp_read_temp(struct k3_thermal_data *devdata,
>> +			    int *temp)
>> +{
>> +	struct k3_bandgap *bgp;
>> +	unsigned int dtemp, s0, s1, s2;
>> +
>> +	bgp = devdata->bgp;
>> +	/**
> 
> "/**" is used to indicate kernel-doc notation in the Linux kernel source files,
> but this comment is not kernel-doc notation, so please just use "/*".

Okay

> 
>> +	 * Errata is applicable for am654 pg 1.0 silicon. There
>> +	 * is a variation of the order for 8-10 degree centigrade.
>> +	 * Work around that by getting the average of two closest
>> +	 * readings out of three readings everytime we want to
>> +	 * report temperatures.
>> +	 *
>> +	 * Errata workaround.
>> +	 */
> thanks.

Thanks for the review.

- Keerthy
>