Re: [PATCH v3 01/13] spi: dt-bindings: allow spi-max-frequency to specify a frequency pair

[Miquel Raynal <miquel.raynal@bootlin.com>]

On 05/06/2026 at 08:17:18 +01, Conor Dooley <conor.dooley@microchip.com> wrote:

> On Fri, Jun 05, 2026 at 08:32:56AM +0200, Miquel Raynal wrote:
>> On 04/06/2026 at 09:36:49 +01, Conor Dooley <conor@kernel.org> wrote:
>> 
>> > On Thu, Jun 04, 2026 at 09:14:16AM +0200, Miquel Raynal wrote:
>> >> Hi Conor,
>> >> 
>> >> >> >> > Right, and this I guess is what scuppers letting the controller driver
>> >> >> >> > sort the configuration out itself and leaving the property as-is.
>> >> >> >> > It could be that the speed in spi-max-frequency is lower than the "base
>> >> >> >> > speed" of the controller but because of board routing or device
>> >> >> >> > capability that the tuned mode is still required, right?
>> >> >> >> 
>> >> >> >> I do not actually expect any tuned mode/frequency to be mandatory.
>> >> >> >
>> >> >> > I think you misunderstood my use of "required", I meant that the new
>> >> >> > property/information was needed in the scenario I described, not that it
>> >> >> > should be a required property in a binding.
>> >> >> 
>> >> >> Yes I misunderstood the term indeed. However I still fail to catch what
>> >> >> you meant here, I'm sorry. Would you mind rephrasing?
>> >> >
>> >> > I was talking about a scenario where you want to use the tuned mode to
>> >> > achieve the maximum rate because of the device and/or board configuration,
>> >> > but the rate is below the point where the controller would need tuning.
>> >> > Say the controller needs tuning above 8 Hz but the conditions require
>> >> > tuning to achieve more than 5 Hz. In this example, if the device can do
>> >> > 6 Hz, spi-max-frequency (in the current form) would be set to 6 Hz, and
>> >> > the controller would not enable the tuned mode, leading to problems
>> >> > because the inflection point determined from the controller compatible
>> >> > of 8 Hz would not have been reached.
>> >> 
>> >> I don't think this is a real situation. If the "conditions", as you say
>> >> (ie. PCB routing, mostly) require tuning above 5, then spi-max-frequency
>> >> should be 5.
>> >
>> > Then tuning mode would never be used.
>> 
>> Well, this is exactly what we propose in this series, a way to indicate
>> two maximum frequencies, one that just works (like before) and a higher
>> frequency that is only reachable after an extra tuning procedure.
>> 
>> > Remember, this is a theoretical world
>> > where spi-max-frequency would contain the tuned frequency and the
>> > controller was using compatible-specific speed thresholds to determine
>> > if tuning was required.
>> 
>> That is not what we are proposing. I don't think indicating the "after
>> tuning" frequency in a property that has long been used for an always
>> reachable frequency is wise. Hence either the use of an array (the
>> second entry could contain a higher frequency) or a secondary
>> spi-max-frequency-whatever property.
>
> I am/was trying to come up with a scenario that would justify the patch
> man, stop trying to interpret it as what I want done.

Ah :-) Sorry the intention was unclear to me. So what is your preferred
take in the end?