On 08/07/2013 04:45 PM, Alexander Shiyan wrote:
>> 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.
As I know the "startup-delay-us" is used for the regulator device, not
the consumer devices.
In this patch, msleep(POWER_ON_DELAY) was used to wait the lm90 stable,
but it seems it's unnecessary now :)
Wei.
>
> ---
>
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