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

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Message-ID: <5201FB2A.2010806@roeck-us.net>
Date:	Wed, 07 Aug 2013 00:45:46 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Alexander Shiyan <shc_work@...l.ru>
CC:	Wei Ni <wni@...dia.com>, khali@...ux-fr.org, swarren@...dotorg.org,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	MLongnecker@...dia.com, linux-tegra@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] hwmon: (lm90) Add power control

On 08/07/2013 12:27 AM, 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@...dia.com>
>> ---
>>   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?
>

Good question. Browsing through other regulator_enable calls,
I don't see a similar delay anywhere else, so one should assume
that this is not necessary.

Guenter

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