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

From: Guenter Roeck
Date: Wed Aug 07 2013 - 03:50:07 EST

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

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.


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