Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for all other voltages

[Vaibhav Hiremath]

On Monday 14 September 2015 03:00 PM, Ulf Hansson wrote:
> [...]
>
> > > > > Could this be implemented by regulator API? From patch set 3/3, the
> > > > > pxa1928
> > > > > voltage_switch hook is to operate the IO pad registers, this seems not
> > > > > belong
> > > > > to the SDHC IP core.
> > > >
> > > > Not quite sure whether regulator would be right fit for this.
> > >
> > >
> > >   From the patche[3/3], this can be achieved by abstracting the IO PAD as
> > > regulators
> > > then, we may not need to touch the core sdhci.c. But I'm not sure whether
> > > this
> > > is the good solution or not.
> >
> >
> > Exactly...
> >
> > > sdhci Maintainers and experts may have better
> > > suggestions.
> >
> > Thats is the reason I stamped it as a RFC :)
>
> [...]
>
>  From an mmc core perspective it would be preferred if you implement
> this as a regulator (vqmmc).
>
> Especially since we will soon have an API for how to set the I/O
> voltages - and the intelligence within that API is not something we
> would like to implement for each and every host driver.
> https://lkml.org/lkml/2015/8/31/367


I would still consider this as a regulator specific and may not address
the IO configuration within the SoC which are module specific.
The API regulator_set_voltage_triplet() will not have intelligence to
differentiate whether the call is coming from MMC or somewhere else.

Note that, the IO pad voltage configuration which I am referring to is
MMC specific and applicable only when pad is configured in MMC mode. So
technically it is not simply common pad voltage configuration.


And I am still not sure regulator framework would be right fit for
this. Pinctrl would have been right fit, but...since I saw f_sdh30
driver is already doing this, which is easy fit; so adopted the same.

Thanks,
Vaibhav
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