Re: [PATCH v6 2/5] iio: adc: add Versal SysMon driver

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 11 Jun 2026 23:27:35 +0100
Salih Erim <salih.erim@amd.com> wrote:

> Add the core driver and MMIO platform driver for the AMD/Xilinx Versal
> System Monitor (SysMon) block.
> 
> The SysMon block resides in the platform management controller (PMC) and
> provides on-chip voltage and temperature monitoring through a 10-bit,
> 200 kSPS ADC. It can monitor up to 160 voltage channels and 64
> temperature satellites distributed across the SoC, with a consistent
> sample rate of 8 kSPS per channel regardless of how many channels are
> enabled.
> 
> The driver is split into two compilation units:
>   - versal-sysmon-core: Channel parsing, IIO registration, read_raw
>   - versal-sysmon: MMIO platform driver with custom regmap accessors
> 
> Voltage results are stored in a 19-bit modified floating-point format
> and converted to millivolts. Temperature results are stored in Q8.7
> signed fixed-point Celsius format and converted to millicelsius.
> 
> The MMIO regmap backend uses a custom reg_write accessor that
> automatically unlocks the NPI (NoC programming interface) lock
> register before each write, as required by the hardware. The regmap
> is configured with fast_io since the underlying MMIO accessors are
> safe to call from atomic context.
> 
> Co-developed-by: Michal Simek <michal.simek@amd.com>
> Signed-off-by: Michal Simek <michal.simek@amd.com>
> Signed-off-by: Salih Erim <salih.erim@amd.com>

One question on the static temp channels. I may have forgotten
some earlier discussion!

> diff --git a/drivers/iio/adc/versal-sysmon-core.c b/drivers/iio/adc/versal-sysmon-core.c
> new file mode 100644
> index 00000000000..c875d156dbe
> --- /dev/null
> +++ b/drivers/iio/adc/versal-sysmon-core.c
> @@ -0,0 +1,281 @@

> +
> +#define SYSMON_CHAN_TEMP(_chan, _address, _name)		\
> +{								\
> +	.type = IIO_TEMP,					\
> +	.indexed = 1,						\
> +	.address = _address,					\
> +	.channel = _chan,					\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> +	.datasheet_name = _name,				\
> +}
> +
> +/* Static temperature channels (always present) */
> +static const struct iio_chan_spec temp_channels[] = {
> +	SYSMON_CHAN_TEMP(0, SYSMON_TEMP_MAX, "temp"),
> +	SYSMON_CHAN_TEMP(1, SYSMON_TEMP_MIN, "min"),
> +	SYSMON_CHAN_TEMP(2, SYSMON_TEMP_MAX_MAX, "max_max"),
> +	SYSMON_CHAN_TEMP(3, SYSMON_TEMP_MIN_MIN, "min_min"),

Sorry, I missed this in previous reviews, but what are these channels?
The labels are rather unusual.

My guess is they are gathering up values from across a bunch of sensors
but I'm not certain. They are unusual enough we probably need some documentation.