On Thu, Dec 03, 2009 at 02:14:23PM +0100, Daniel Mack wrote:
> On Thu, Dec 03, 2009 at 01:06:27PM +0000, Mark Brown wrote:
> > This is historical, they can all be converted to regulator_get_exclusive()
> > so the move to the core (while good) isn't required for this reason.
> Is it? What if you share one regulator for two slots? While this isn't a
> problem I have met in real life, this should still be considered.
I agree, this is a configuration which I have also seen, but there was a
strong insistence that the power off had to function as expected. An
approach which allows shared regulators is generally always preferable
since it copes with a wider range of system designs.
> The problem I _did_ see, however, was a warning when the regulator was
> marked as always_on in its constraints. What happens then is that
> regulator_is_enabled() will always return 1, causing the pxamci code to
...
> Making those drivers claim their regulators exclusively _does_ solve the
> first problem, but not the latter.
Yeah, there's currently an assumption that the constraints will be
suitable for the driver there. A driver that can handle sharing should
always cope here, it's one reason to prefer them.
> > > case MMC_POWER_OFF:
> > > - if(host->vcc &&
> > > - regulator_is_enabled(host->vcc))
> > > - regulator_disable(host->vcc);
> > > + if(mmc->vcc && mmc->vcc_enabled) {
> > > + regulator_disable(mmc->vcc);
> > > + mmc->vcc_enabled = 0;
> > > + }
> > Can the MMC core actually tolerate the MMC power not getting killed when
> > expected? My understanding from previous discussion was that it wasn't
> > able to do so. If it is then conversion to using regulator_get_exclusive()
> > isn't desirable, of course.
> I would expect the power to be killed when the last user stops using it.
> Which should result in the same effect if you only have one host, one
> regulator, and one user.
Yes, it's always fine in that case (modulo always_on and/or regulators
without power control). This goes back to the thing about using
regulator_get_exclusive(), the message given was that the MMC drivers
really needed to be able to guarantee that the power would be removed
when that was requested.
Like I say, if there isn't a *strict* requirement but it's only
desirable (possibly strongly desirable) then your approach is obviously
preferable.
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