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Sender: Guenter Roeck <groeck7@gmail.com>
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Date: Wed, 24 Jan 2024 22:54:07 -0800
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Subject: Re: [PATCH V3] hwmon: scmi-hwmon: implement change_mode for thermal
 zones
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To: "Peng Fan (OSS)" <peng.fan@oss.nxp.com>, groeck7@gmail.com,
 sudeep.holla@arm.com, cristian.marussi@arm.com, jdelvare@suse.com
Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org,
 Peng Fan <peng.fan@nxp.com>
References: <20240125064422.347002-1-peng.fan@oss.nxp.com>
From: Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20240125064422.347002-1-peng.fan@oss.nxp.com>
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On 1/24/24 22:44, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
> 
> The thermal sensors maybe disabled before kernel boot, so add change_mode
> for thermal zones to support configuring the thermal sensor to enabled
> state. If reading the temperature when the sensor is disabled, there will
> be error reported.
> 
> The cost is an extra config_get all to SCMI firmware to get the status
> of the thermal sensor. No function level impact.
> 
> Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
> 
> V3:
>   Update commit log to show it only applys to thermal
>   Add comments in code
>   Add R-b from Cristian
> 

You didn't address my question regarding the behavior of hwmon
attributes if a sensor is disabled.

>   Guenter, I Cced linux@roeck-us.net when sending V1/V2
>   Let me Cc Guenter Roeck <groeck7@gmail.com> in V3, hope you not mind
> 
This time I received it twice ;-).

> V2:
>   Use SCMI_SENS_CFG_IS_ENABLED & clear BIT[31:9] before update config(Thanks Cristian)
> 
>   drivers/hwmon/scmi-hwmon.c | 39 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
> index 364199b332c0..af2267fea5f0 100644
> --- a/drivers/hwmon/scmi-hwmon.c
> +++ b/drivers/hwmon/scmi-hwmon.c
> @@ -151,7 +151,46 @@ static int scmi_hwmon_thermal_get_temp(struct thermal_zone_device *tz,
>   	return ret;
>   }
>   
> +static int scmi_hwmon_thermal_change_mode(struct thermal_zone_device *tz,
> +					  enum thermal_device_mode new_mode)
> +{
> +	int ret;
> +	u32 config;
> +	enum thermal_device_mode cur_mode = THERMAL_DEVICE_DISABLED;
> +	struct scmi_thermal_sensor *th_sensor = thermal_zone_device_priv(tz);
> +
> +	ret = sensor_ops->config_get(th_sensor->ph, th_sensor->info->id,
> +				     &config);
> +	if (ret)
> +		return ret;
> +
> +	if (SCMI_SENS_CFG_IS_ENABLED(config))
> +		cur_mode = THERMAL_DEVICE_ENABLED;
> +
> +	if (cur_mode == new_mode)
> +		return 0;
> +
> +	/*
> +	 * Per SENSOR_CONFIG_SET sensor_config description:
> +	 * BIT[31:11] should be set to 0 if the sensor update interval does
> +	 * not need to be updated, so clear them.
> +	 * And SENSOR_CONFIG_GET does not return round up/down, so also clear
> +	 * BIT[10:9] round up/down.

What does "clear" mean ? Is it going to round up ? Round down ? And why would it
be necessary to clear those bits if SENSOR_CONFIG_GET does not return the
current setting in the first place ?

Thanks,
Guenter

> +	 */
> +	config &= ~(SCMI_SENS_CFG_UPDATE_SECS_MASK |
> +		    SCMI_SENS_CFG_UPDATE_EXP_MASK |
> +		    SCMI_SENS_CFG_ROUND_MASK);
> +	if (new_mode == THERMAL_DEVICE_ENABLED)
> +		config |= SCMI_SENS_CFG_SENSOR_ENABLED_MASK;
> +	else
> +		config &= ~SCMI_SENS_CFG_SENSOR_ENABLED_MASK;
> +
> +	return sensor_ops->config_set(th_sensor->ph, th_sensor->info->id,
> +				      config);
> +}
> +
>   static const struct thermal_zone_device_ops scmi_hwmon_thermal_ops = {
> +	.change_mode = scmi_hwmon_thermal_change_mode,
>   	.get_temp = scmi_hwmon_thermal_get_temp,
>   };
>