[PATCH 11/12] hwmon: spd5118: Add I3C support

[Guenter Roeck]

On 3/18/26 10:27, Akhil R wrote:
> Add a regmap config and a probe function to support for I3C based
> communication to SPD5118 devices.
> 
> On an I3C bus, SPD5118 are enumerated via SETAASA and always require an
> ACPI or device tree entry. The device matching is hence through the OF
> match tables only and do not need an I3C class match table. The device
> identity is verified in the type registers before proceeding to the
> common probe function.
> 
> Signed-off-by: Akhil R <akhilrajeev at nvidia.com>
> ---
>   drivers/hwmon/Kconfig   |  7 +++--
>   drivers/hwmon/spd5118.c | 66 ++++++++++++++++++++++++++++++++++++++++-
>   2 files changed, 70 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 8af80e17d25e..23604c05ad22 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -2300,10 +2300,13 @@ config SENSORS_SPD5118
>   	tristate "SPD5118 Compliant Temperature Sensors"
>   	depends on I2C
>   	select REGMAP_I2C

I also had
	depends on I3C || I3C=n
in my version at

https://patchwork.kernel.org/project/linux-hwmon/patch/20250419161356.2528986-6-linux@roeck-us.net/

which I guess matches the more recent "depends on I3C_OR_I2C".

> +	select REGMAP_I3C if I3C
>   	help
>   	  If you say yes here you get support for SPD5118 (JEDEC JESD300)
> -	  compliant temperature sensors. Such sensors are found on DDR5 memory
> -	  modules.
> +	  compliant temperature sensors using I2C or I3C bus interface.
> +	  Such sensors are found on DDR5 memory modules.
> +
> +	  This driver supports both I2C and I3C interfaces.
>   
>   	  This driver can also be built as a module. If so, the module
>   	  will be called spd5118.
> diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c
> index 5da44571b6a0..d70123e10616 100644
> --- a/drivers/hwmon/spd5118.c
> +++ b/drivers/hwmon/spd5118.c
> @@ -18,6 +18,7 @@
>   #include <linux/bits.h>
>   #include <linux/err.h>
>   #include <linux/i2c.h>
> +#include <linux/i3c/device.h>
>   #include <linux/hwmon.h>
>   #include <linux/module.h>
>   #include <linux/mutex.h>
> @@ -482,6 +483,25 @@ static const struct regmap_config spd5118_regmap16_config = {
>   	.cache_type = REGCACHE_MAPLE,
>   };
>   
> +/*
> + * I3C uses 2-byte register addressing -
> + *   Byte 1: MemReg | BlkAddr[0] | Address[5:0]
> + *   Byte 2: 0000   | BlkAddr[4:1]
> + *
> + * The low byte carries the register/NVM address and the high byte carries the
> + * upper block address bits, so little-endian format is required. No range
> + * config is needed since I3C does not use MR11 page switching.
> + */
> +static const struct regmap_config spd5118_regmap_i3c_config = {
> +	.reg_bits = 16,
> +	.val_bits = 8,
> +	.max_register = 0x7ff,
> +	.reg_format_endian = REGMAP_ENDIAN_LITTLE,

Should this be added to spd5118_regmap16_config instead, or is there reason
to assume that I2C 16-bit addressing differs from I3C addressing ?

> +	.writeable_reg = spd5118_writeable_reg,
> +	.volatile_reg = spd5118_volatile_reg,
> +	.cache_type = REGCACHE_MAPLE,
> +};
> +
>   static int spd5118_suspend(struct device *dev)
>   {
>   	struct spd5118_data *data = dev_get_drvdata(dev);
> @@ -770,7 +790,51 @@ static struct i2c_driver spd5118_i2c_driver = {
>   	.address_list	= IS_ENABLED(CONFIG_SENSORS_SPD5118_DETECT) ? normal_i2c : NULL,
>   };
>   
> -module_i2c_driver(spd5118_i2c_driver);
> +/* I3C */
> +
> +static int spd5118_i3c_probe(struct i3c_device *i3cdev)
> +{
> +	struct device *dev = i3cdev_to_dev(i3cdev);
> +	struct regmap *regmap;
> +	unsigned int regval;
> +	int err;
> +
> +	regmap = devm_regmap_init_i3c(i3cdev, &spd5118_regmap_i3c_config);
> +	if (IS_ERR(regmap))
> +		return dev_err_probe(dev, PTR_ERR(regmap), "regmap init failed\n");
> +
> +	/* Verify this is a SPD5118 device */
> +	err = regmap_read(regmap, SPD5118_REG_TYPE, &regval);
> +	if (err)
> +		return err;
> +
> +	if (regval != 0x51) {
> +		dev_err(dev, "unexpected device type 0x%02x, expected 0x51\n", regval);
> +		return -ENODEV;
> +	}
> +
> +	err = regmap_read(regmap, SPD5118_REG_TYPE + 1, &regval);
> +	if (err)
> +		return err;
> +
> +	if (regval != 0x18) {
> +		dev_err(dev, "unexpected device type 0x%02x, expected 0x18\n", regval);
> +		return -ENODEV;
> +	}
> +

I don't think this should dump error messages. Also, it might be desirable
to use a single regmap operation to read both values.

> +	return spd5118_common_probe(dev, regmap, false);

Why is_16bit=false ?

Thanks,
Guenter

> +}
> +
> +static struct i3c_driver spd5118_i3c_driver = {
> +	.driver = {
> +		.name	= "spd5118_i3c",
> +		.of_match_table = spd5118_of_ids,
> +		.pm = pm_sleep_ptr(&spd5118_pm_ops),
> +	},
> +	.probe		= spd5118_i3c_probe,
> +};
> +
> +module_i3c_i2c_driver(spd5118_i3c_driver, &spd5118_i2c_driver);
>   
>   MODULE_AUTHOR("René Rebe <rene at exactcode.de>");
>   MODULE_AUTHOR("Guenter Roeck <linux at roeck-us.net>");