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

[Vaibhav Hiremath]

On Wednesday 02 September 2015 01:56 PM, Jisheng Zhang wrote:
> On Wed, 2 Sep 2015 13:49:53 +0530
> Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx> wrote:
>
> > On Wednesday 02 September 2015 12:34 PM, Jisheng Zhang wrote:
> > > On Wed, 2 Sep 2015 01:02:17 +0530
> > > Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx> wrote:
> > >
> > > > Currently, the sdhci_do_start_signal_voltage_switch() function invokes
> > > > controller specific voltage switch configuration only for 1.8v usecase;
> > > > but it is required for others as well.
> > > >
> > > > For example, in case of PXA1928 SDH controller, we need to set different
> > > > configuration for 3.3, 1.8 and 1.2 volt support (I/O domain power
> > > > control register).
> > > >
> > > > Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx>
> > > > ---
> > > > Note:
> > > > Currently ->voltage_switch() callback is only supported
> > > > in f_sdh30 driver. And I am not sure on the dependency of execution
> > > > sequence for that device. I could have moved ->voltage_switch() call
> > > > at one common place (above/below), but was not quite sure about it.
> > > > So, replicated/duplicated the call for other voltages.
> > > >
> > > >    drivers/mmc/host/sdhci.c | 8 ++++++++
> > > >    1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > > > index 3dd295f..b59b76d 100644
> > > > --- a/drivers/mmc/host/sdhci.c
> > > > +++ b/drivers/mmc/host/sdhci.c
> > > > @@ -1753,6 +1753,10 @@ static int sdhci_do_start_signal_voltage_switch(struct sdhci_host *host,
> > > >    		/* Wait for 5ms */
> > > >    		usleep_range(5000, 5500);
> > > >
> > > > +		/* Some controller need to do more when switching */
> > > > +		if (host->ops->voltage_switch)
> > > > +			host->ops->voltage_switch(host, MMC_SIGNAL_VOLTAGE_330);
> > >
> > > 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 :)

Thanks,
Vaibhav
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