Re: [PATCH v5 5/7] iio: adc: ad4030: Add SPI offload support

[Nuno Sá]

On Fri, 2025-10-17 at 08:35 -0300, Marcelo Schmitt wrote:
> On 10/16, David Lechner wrote:
> > On 10/14/25 5:22 PM, Marcelo Schmitt wrote:
> > > AD4030 and similar ADCs can capture data at sample rates up to 2 mega
> > > samples per second (MSPS). Not all SPI controllers are able to achieve
> > > such
> > > high throughputs and even when the controller is fast enough to run
> > > transfers at the required speed, it may be costly to the CPU to handle
> > > transfer data at such high sample rates. Add SPI offload support for
> > > AD4030
> > > and similar ADCs to enable data capture at maximum sample rates.
> > > 
> > > Co-developed-by: Trevor Gamblin <tgamblin@xxxxxxxxxxxx>
> > > Signed-off-by: Trevor Gamblin <tgamblin@xxxxxxxxxxxx>
> > > Co-developed-by: Axel Haslam <ahaslam@xxxxxxxxxxxx>
> > > Signed-off-by: Axel Haslam <ahaslam@xxxxxxxxxxxx>
> > > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
> > > ---
> > > Change log v4 -> v5
> > > - Made Kconfig entry depend on PWM and select other features.
> > > - Reused ad4030_exit_config_mode() in ad4030_offload_buffer_postenable().
> > > - Dropped common-mode voltage support on SPI offload setup.
> > 
> > Curious why you chose this. I guess it will be fine to add it later
> > if anyone ever actually needs it.
> > 
> I had coded that in a way I think would work for the dual channel devices, but
> it didn't really work for single-channel adaq4216. And yes, if anyone asks
> for offload with common-mode data, we shall probably be able to it that later.

I guess that if someone really wants it, the data will still be available in the
sample. But yes, it would be nice to properly support it at some point.

- Nuno Sá