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

[Conor Dooley <conor.dooley@microchip.com>]

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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.

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