Re: [PATCH 2/2] hwmon: (sy7636a) enable regulator only if needed

Guenter Roeck
2025-09-24T21:06:59Z

On 9/24/25 13:40, Andreas Kemnade wrote:
> On Wed, 24 Sep 2025 09:06:15 -0700
> Guenter Roeck <linux@roeck-us.net> wrote:
>
>> On Sat, Sep 20, 2025 at 01:43:11PM +0200, Andreas Kemnade wrote:
>>> Avoid having all the regulators in the SY7636A enabled all the time
>>> to significantly reduce current consumption. In pratical scenarios,
>>> the regulators are only needed when a refresh is done on the epaper
>>> display powered by the SY7636A. This is can save around 10mA which
>>> is much for this kind of devices.
>>> Also fixes the asymmetrical single enable call.
>>>
>>> Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
>>> ---
>>> drivers/hwmon/sy7636a-hwmon.c | 34 ++++++++++++++++++++++++----------
>>> 1 file changed, 24 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/hwmon/sy7636a-hwmon.c b/drivers/hwmon/sy7636a-hwmon.c
>>> index e83d0e50c735..0fda69bea3b4 100644
>>> --- a/drivers/hwmon/sy7636a-hwmon.c
>>> +++ b/drivers/hwmon/sy7636a-hwmon.c
>>> @@ -18,14 +18,26 @@
>>>
>>> #include <linux/mfd/sy7636a.h>
>>>
>>> +struct sy7636a_hwmon_data {
>>> + struct regmap *regmap;
>>> + struct regulator *regulator;
>>> +};
>>> +
>>> +
>>> static int sy7636a_read(struct device *dev, enum hwmon_sensor_types type,
>>> u32 attr, int channel, long *temp)
>>> {
>>> - struct regmap *regmap = dev_get_drvdata(dev);
>>> + struct sy7636a_hwmon_data *drvdata = dev_get_drvdata(dev);
>>> int ret, reg_val;
>>>
>>> - ret = regmap_read(regmap,
>>> + ret = regulator_enable(drvdata->regulator);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + ret = regmap_read(drvdata->regmap,
>>> SY7636A_REG_TERMISTOR_READOUT, &reg_val);
>>
>> Does that really work without delay ? Usually it takes some time for a chip
>> to return useful data after its power supply has been enabled. calls
>>
> Hmm, enabling the onoff bit behind the regulator is just needed to turn
> ADC on here. But there is also the power good wait which should usually be enough.
> Usually... But there is no guarantee. So yes, better wait for one adc aquisition.
>

Would that be the power good timeout (50ms) ? The conversion time on top if that
is not much, but the power good wait is a long time. That strongly suggests that
this should be made optional. Not everyone might like the additional delay for
each temperature reading.

Guenter