Re: [PATCH 11/12] hwmon: spd5118: Add I3C support
From: Alexandre Belloni
Date: Wed Mar 18 2026 - 14:31:40 EST
On 18/03/2026 22:57:24+0530, 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@xxxxxxxxxx>
> ---
> 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
Please use I3C_OR_I2C here
> select REGMAP_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,
> + .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, ®val);
> + 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, ®val);
> + if (err)
> + return err;
> +
> + if (regval != 0x18) {
> + dev_err(dev, "unexpected device type 0x%02x, expected 0x18\n", regval);
> + return -ENODEV;
> + }
> +
> + return spd5118_common_probe(dev, regmap, false);
> +}
> +
> +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@xxxxxxxxxxxx>");
> MODULE_AUTHOR("Guenter Roeck <linux@xxxxxxxxxxxx>");
> --
> 2.50.1
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com