> On 08/07/2013 03:50 PM, Guenter Roeck wrote:
> > On 08/07/2013 12:32 AM, Wei Ni wrote:
> >> On 08/07/2013 03:27 PM, Alexander Shiyan wrote:
> >>>> The device lm90 can be controlled by the vdd rail.
> >>>> Adding the power control support to power on/off the vdd rail.
> >>>> And make sure that power is enabled before accessing the device.
> >>>>
> >>>> Signed-off-by: Wei Ni <wni@xxxxxxxxxx>
> >>>> ---
> >>>> drivers/hwmon/lm90.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >>> [...]
> >>>> + if (!data->lm90_reg) {
> >>>> + data->lm90_reg = regulator_get(&client->dev, "vdd");
> >>>> + if (IS_ERR_OR_NULL(data->lm90_reg)) {
> >>>> + if (PTR_ERR(data->lm90_reg) == -ENODEV)
> >>>> + dev_info(&client->dev,
> >>>> + "No regulator found for vdd. Assuming vdd is always powered.");
> >>>> + else
> >>>> + dev_warn(&client->dev,
> >>>> + "Error [%ld] in getting the regulator handle for vdd.\n",
> >>>> + PTR_ERR(data->lm90_reg));
> >>>> + data->lm90_reg = NULL;
> >>>> + mutex_unlock(&data->update_lock);
> >>>> + return -ENODEV;
> >>>> + }
> >>>> + }
> >>>> + if (is_enable) {
> >>>> + ret = regulator_enable(data->lm90_reg);
> >>>> + msleep(POWER_ON_DELAY);
> >>>
> >>> Can this delay be handled directly from regulator?
> >>
> >> I think it should be handled in the device driver.
> >> Because there have different delay time to wait devices stable.
> >>
> >
> > Then why does no other caller of regulator_enable() need this ?
> > I don't think lm90 is so much different to other users of regulator
> > functionality.
>
> May be I'm wrong. I noticed that in lm90 SPEC, the max of "SMBus Clock
> Low Time" is 25ms, so I supposed that it may need about 20ms to stable
> after power on.
>
> Anyway, if I remove this delay, the driver also works fine, so I will
> remove it in my next patch.
I originally had in mind that regulator API contain own delay option.
E.g. reg-fixed-voltage && gpio-regulator contains "startup-delay-us" property.
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