linux-kernel - Re: [PATCH] hwmon: ina238: Report energy in microjoules

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Message-ID: <a42af051-c9d2-44bc-a8ca-2dcbe9380863@roeck-us.net>
Date: Tue, 15 Jul 2025 10:37:59 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Jonas Rebmann <jre@...gutronix.de>
Cc: Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
	linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, Wenliang Yan <wenliang202407@....com>,
	kernel@...gutronix.de
Subject: Re: [PATCH] hwmon: ina238: Report energy in microjoules

On Tue, Jul 15, 2025 at 03:02:41PM +0200, Jonas Rebmann wrote:
> The hwmon sysfs interface specifies that energy values should be
> reported in microjoules. This is also what tools such as lmsensors
> expect, reporting wrong values otherwise.
> 
> Adjust the driver to scale the output accordingly and adjust ina238
> driver documentation.
> 
> Fixes: 6daaf15a1173 ("hwmon: (ina238) Add support for SQ52206")
> Signed-off-by: Jonas Rebmann <jre@...gutronix.de>

Applied.

Guenter
> ---
> This is a fix for a bug introduced into ina238.c recently (6daaf15a1173
> ("hwmon: (ina238) Add support for SQ52206")) and merged into
> v6.16-rc1.
> 
> Jean, Guenter, can you include this for 6.16, please?
> ---
>  Documentation/hwmon/ina238.rst | 2 +-
>  drivers/hwmon/ina238.c         | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> 
> ---
> base-commit: 155a3c003e555a7300d156a5252c004c392ec6b0
> change-id: 20250715-hwmon-ina238-microjoules-3d8edaa5ded0
> 
> Best regards,
> 
> diff --git a/Documentation/hwmon/ina238.rst b/Documentation/hwmon/ina238.rst
> index d1b93cf8627f352612f17953c62efc5ef5596fe5..9a24da4786a43f7493b364b005b2ae9992c3b10d 100644
> --- a/Documentation/hwmon/ina238.rst
> +++ b/Documentation/hwmon/ina238.rst
> @@ -65,7 +65,7 @@ Additional sysfs entries for sq52206
>  ------------------------------------
>  
>  ======================= =======================================================
> -energy1_input		Energy measurement (mJ)
> +energy1_input		Energy measurement (uJ)
>  
>  power1_input_highest	Peak Power (uW)
>  ======================= =======================================================
> diff --git a/drivers/hwmon/ina238.c b/drivers/hwmon/ina238.c
> index a4a41742786bd19e1c5dab34c7d71973527161a1..9a5fd16a4ec2a6d5a6cd5e8070d0442e1ef0135a 100644
> --- a/drivers/hwmon/ina238.c
> +++ b/drivers/hwmon/ina238.c
> @@ -97,7 +97,7 @@
>   *  Power (mW) = 0.2 * register value * 20000 / rshunt / 4 * gain
>   *  (Specific for SQ52206)
>   *  Power (mW) = 0.24 * register value * 20000 / rshunt / 4 * gain
> - *  Energy (mJ) = 16 * 0.24 * register value * 20000 / rshunt / 4 * gain
> + *  Energy (uJ) = 16 * 0.24 * register value * 20000 / rshunt / 4 * gain * 1000
>   */
>  #define INA238_CALIBRATION_VALUE	16384
>  #define INA238_FIXED_SHUNT		20000
> @@ -500,9 +500,9 @@ static ssize_t energy1_input_show(struct device *dev,
>  	if (ret)
>  		return ret;
>  
> -	/* result in mJ */
> -	energy = div_u64(regval * INA238_FIXED_SHUNT *	data->gain * 16 *
> -				data->config->power_calculate_factor, 4 * 100 * data->rshunt);
> +	/* result in uJ */
> +	energy = div_u64(regval * INA238_FIXED_SHUNT *	data->gain * 16 * 10 *
> +				data->config->power_calculate_factor, 4 * data->rshunt);
>  
>  	return sysfs_emit(buf, "%llu\n", energy);
>  }