Re: [PATCH 2/3] platform: arm64: qcom-hamoa-ec: Add thermistor sensors

[Ilpo Järvinen]

On Mon, 28 Sep 2026, Anvesh Jain P wrote:

> The Qualcomm embedded controller has exclusive access to multiple onboard
> thermistors programmatically discoverable through the
> EC_THERMAL_CAPABILITIES command. The temperature values are reported in
> degree Celsius through the EC_THERMISTOR_TEMP_CMD.
> 
> Register these thermistors with the thermal framework by adding support to
> the EC_THERMISTOR_TEMP_CMD and convert it to millidegree units as required
> by the thermal framework.
> 
> Signed-off-by: Anvesh Jain P <anvesh.p@xxxxxxxxxxxxxxxx>
> ---
>  drivers/platform/arm64/qcom-hamoa-ec.c | 74 ++++++++++++++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
> 
> diff --git a/drivers/platform/arm64/qcom-hamoa-ec.c b/drivers/platform/arm64/qcom-hamoa-ec.c
> index 4d2ad042a7f8..acf3d7f53026 100644
> --- a/drivers/platform/arm64/qcom-hamoa-ec.c
> +++ b/drivers/platform/arm64/qcom-hamoa-ec.c
> @@ -16,16 +16,19 @@
>  #include <linux/pm.h>
>  #include <linux/slab.h>
>  #include <linux/thermal.h>
> +#include <linux/unaligned.h>
>  
>  #define EC_SCI_EVT_READ_CMD	0x05
>  #define EC_FW_VERSION_CMD	0x0e
>  #define EC_MODERN_STANDBY_CMD	0x23
> +#define EC_THERMISTOR_TEMP_CMD	0x29	/* + thermistor_id (0-6) selects thermistor 1-7 */
>  #define EC_FAN_DBG_CONTROL_CMD	0x30
>  #define EC_SCI_EVT_CONTROL_CMD	0x35
>  #define EC_THERMAL_CAP_CMD	0x42
>  
>  #define EC_FW_VERSION_RESP_LEN	4
>  #define EC_THERMAL_CAP_RESP_LEN	3
> +#define EC_THERMISTOR_TEMP_RESP_LEN	3
>  #define EC_FAN_DEBUG_CMD_LEN	6
>  #define EC_FAN_SPEED_DATA_SIZE	4
>  
> @@ -39,6 +42,7 @@
>  #define EC_MAX_FAN_CNT		2
>  #define EC_FAN_NAME_SIZE	20
>  #define EC_FAN_MAX_PWM		255
> +#define EC_MAX_THERMISTOR_CNT	7
>  
>  enum qcom_ec_sci_events {
>  	EC_FAN1_STATUS_CHANGE_EVT = 0x30,
> @@ -64,6 +68,7 @@ struct qcom_ec_thermal_cap {
>  #define EC_THERMAL_FAN_CNT(x)		(FIELD_GET(GENMASK(1, 0), (x)))
>  #define EC_THERMAL_FAN_TYPE(x)		(FIELD_GET(GENMASK(4, 2), (x)))
>  #define EC_THERMAL_THERMISTOR_MASK(x)	(FIELD_GET(GENMASK(7, 0), (x)))
> +#define EC_THERMISTOR_PRESENT(mask, id)	((mask) & BIT(id))
>  	u8 fan_cnt;
>  	u8 fan_type;
>  	u8 thermistor_mask;
> @@ -81,6 +86,12 @@ struct qcom_ec {
>  	struct qcom_ec_thermal_cap thermal_cap;
>  	struct qcom_ec_version version;
>  	struct i2c_client *client;
> +	struct qcom_ec_thermal_zone *ec_tz;
> +};
> +
> +struct qcom_ec_thermal_zone {
> +	struct qcom_ec *ec;
> +	u8 thermistor_id;
>  };
>  
>  static int qcom_ec_read(struct qcom_ec *ec, u8 cmd, u8 resp_len, u8 *resp)
> @@ -183,6 +194,43 @@ static int qcom_ec_thermal_capabilities(struct device *dev)
>  	return 0;
>  }
>  
> +/*
> + * EC Thermistor Temperature (cmd 0x29 + thermistor_id, id 0-6 selects
> + * thermistor 1-7):
> + *
> + * Read Response:
> + * ----------------------------------------------------------------------
> + * | Offset	| Name		| Description				|
> + * ----------------------------------------------------------------------
> + * | 0x00	| Byte count	| Number of bytes in response (=2)	|
> + * ----------------------------------------------------------------------
> + * | 0x01 (LSB)| Temperature	| Signed 16-bit, unit of 0.1 degC,	|
> + * | 0x02 (MSB)|		| range -40..+125 degC			|
> + * ----------------------------------------------------------------------
> + */
> +static int qcom_ec_thermistor_get_temp(struct thermal_zone_device *tz, int *temp)
> +{
> +	struct qcom_ec_thermal_zone *ec_tz = thermal_zone_device_priv(tz);
> +	struct qcom_ec *ec = ec_tz->ec;
> +	u8 resp[EC_THERMISTOR_TEMP_RESP_LEN];
> +	s16 raw;
> +	int ret;
> +
> +	ret = qcom_ec_read(ec, EC_THERMISTOR_TEMP_CMD + ec_tz->thermistor_id,
> +			   EC_THERMISTOR_TEMP_RESP_LEN, resp);
> +	if (ret < 0)
> +		return ret;
> +
> +	raw = (s16)get_unaligned_le16(&resp[1]);
> +	*temp = raw * 100;

MILLIDEGREE_PER_DECIDEGREE?

Make sure you have the include for it if changing to it.

> +
> +	return 0;
> +}
> +
> +static const struct thermal_zone_device_ops qcom_ec_thermistor_ops = {
> +	.get_temp = qcom_ec_thermistor_get_temp,
> +};
> +
>  static irqreturn_t qcom_ec_irq(int irq, void *data)
>  {
>  	struct qcom_ec *ec = data;
> @@ -376,6 +424,32 @@ static int qcom_ec_probe(struct i2c_client *client)
>  	if (ret < 0)
>  		return dev_err_probe(dev, ret, "Failed to read thermal capabilities\n");
>  
> +	if (ec->thermal_cap.thermistor_mask) {
> +		ec->ec_tz = devm_kcalloc(dev, EC_MAX_THERMISTOR_CNT, sizeof(*ec->ec_tz),
> +					 GFP_KERNEL);
> +		if (!ec->ec_tz)
> +			return -ENOMEM;
> +
> +		for (i = 0; i < EC_MAX_THERMISTOR_CNT; i++) {
> +			struct qcom_ec_thermal_zone *ec_tz = &ec->ec_tz[i];
> +			struct thermal_zone_device *tzd;
> +
> +			if (!EC_THERMISTOR_PRESENT(ec->thermal_cap.thermistor_mask, i))
> +				continue;
> +
> +			ec_tz->ec = ec;
> +			ec_tz->thermistor_id = i;
> +
> +			tzd = devm_thermal_of_zone_register(dev, i, ec_tz, &qcom_ec_thermistor_ops);
> +			if (IS_ERR(tzd)) {
> +				ret = PTR_ERR(tzd);
> +				if (ret != -ENODEV)

I'd prefer ret == -ENODEV check + continue.

> +					dev_warn(dev, "Failed to register thermistor%u zone: %d\n",
> +						 i, ret);
> +			}
> +		}
> +	}
> +
>  	if (ec->thermal_cap.fan_cnt == 0) {
>  		dev_warn(dev, FW_BUG "Failed to get fan count, firmware update required\n");
>  		return 0;
> 
> 

-- 
 i.