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

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Message-ID: <ab0bc84b-189f-a9be-e838-a38c14fa702a@infradead.org>
Date:   Tue, 18 Feb 2020 23:50:29 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Keerthy <j-keerthy@...com>, 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 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?

> +	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 "/*".

> +	 * 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.
-- 
~Randy