Re: [PATCH 1/2] hwmon: (lm90) Add power control

[Guenter Roeck]

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.

Besides that, your delay is unconditional, even for static regulators
which are always on. Other callers of regulator_enable() don't need
all that complexity, which I take as sign that it is not needed here either.

Guenter

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