Re: [PATCH v2 2/5] iio: adc: add Versal SysMon driver

[Salih Erim <salih.erim@amd.com>]

Hi Guenter and Jonathan,

On 5/4/2026 8:26 PM, Guenter Roeck wrote:
> 
> 
> On 5/4/26 10:32, Jonathan Cameron wrote:
>> On Sat, 2 May 2026 12:19:48 +0100
>> Salih Erim <salih.erim@amd.com> wrote:
>>
>>> Add the AMD/Xilinx Versal System Monitor (SysMon) IIO driver.
>>>
>>> The driver is split into a bus-agnostic core module
>>> (versal-sysmon-core) and a memory-mapped I/O platform driver
>>> (versal-sysmon). The core uses the regmap API so that different
>>> bus implementations can share the same IIO logic.
>>>
>>> The core provides:
>>>    - Static temperature channels (current max/min, peak max/min)
>>>    - Supply voltage channels parsed from DT container nodes
>>>    - Temperature satellite channels parsed from DT container nodes
>>>    - read_raw for IIO_CHAN_INFO_RAW and IIO_CHAN_INFO_PROCESSED
>>>    - read_label using the DT label property
>>
>> Various comments inline.  One thing to check.
>> Is this one strictly a hardware monitoring device? Or does it
>> get used for more general ADC purposes?  Did you consider an HWMON driver
>> for it? The above sounds a lot like hwmon. So why IIO for this one?
>>
>> I wasn't awake enough on v1 to raise this!  Sorry about that.
>> +CC Guenter and linux-hwmon for that discussion.
>>
> 
> This very much sounds like a hardware monitoring device to me.

The device is indeed used for hardware monitoring, but the hardware
characteristics push it towards IIO:

- The predecessor (Zynq UltraScale+ AMS, xilinx-ams.c) is already
   in drivers/iio/adc/ upstream. This driver is the direct successor
   for the Versal generation.

- The supply voltage encoding is a modified floating-point format
   with per-register exponent and format bits. This non-linear
   encoding doesn't map well to hwmon's linear in*_input model.

- The device has configurable threshold events with per-channel
   alarm registers, hysteresis bits, and level-sensitive interrupt
   masking/unmasking -- which maps directly to the IIO event
   infrastructure.

- Oversampling is hardware-configurable per channel type with
   per-channel averaging enable registers.

- Up to 160 voltage and 64 temperature channels are dynamically
   configured from DT, which fits IIO's dynamic channel model
   better than hwmon's compile-time attribute groups.

- The follow-up thermal driver uses the IIO consumer API
   (iio_channel_read) to aggregate temperature data across
   multiple satellites into thermal zones. The iio-hwmon bridge
   then exposes the same data to hwmon userspace.

So the architecture is: IIO driver (provider) -> iio-hwmon bridge
(hwmon exposure) + IIO consumer (thermal zones). This gives both
hwmon and thermal framework access through a single IIO provider.
> 
> Guenter
> 

Salih.