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Date:   Thu, 6 Jul 2023 17:36:49 +0200
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From:   Mike Looijmans <mike.looijmans@topic.nl>
Subject: Re: [PATCH 2/2] Input: exc3000 - Support power supply regulators
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
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On 05-07-2023 23:49, Dmitry Torokhov wrote:
> Hi Mike,
>
> On Mon, Jul 03, 2023 at 10:45:36AM +0200, Mike Looijmans wrote:
>> Add power supply regulator support to the exc3000 devices.
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
>>
>> ---
>>
>>   drivers/input/touchscreen/exc3000.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchsc=
reen/exc3000.c
>> index 4af4c1e5d0da..3e50af8a4a2d 100644
>> --- a/drivers/input/touchscreen/exc3000.c
>> +++ b/drivers/input/touchscreen/exc3000.c
>> @@ -18,6 +18,7 @@
>>   #include <linux/interrupt.h>
>>   #include <linux/module.h>
>>   #include <linux/of.h>
>> +#include <linux/regulator/consumer.h>
>>   #include <linux/sizes.h>
>>   #include <linux/timer.h>
>>   #include <asm/unaligned.h>
>> @@ -360,6 +361,12 @@ static int exc3000_probe(struct i2c_client *client)
>>   	if (IS_ERR(data->reset))
>>   		return PTR_ERR(data->reset);
>>  =20
>> +	/* For proper reset sequence, enable power while reset asserted */
>> +	error =3D devm_regulator_get_enable_optional(&client->dev, "vdd");
>> +	if (error && error !=3D -ENODEV)
>> +		dev_err_probe(&client->dev, error,
>> +			      "failed to request vdd regulator\n");
>
> If there is a regulator described in the firmware we should not continue
> with initializing the device if we fail to grab/enable it. Think about
> what happens if you get -EPROBE_DEFER here. You should return here.

True, good catch, I forgot the "return" here (which in all honesty was=20
the reason for using dev_err_probe in the first place...).

> Also, why are you using the _optional() variant? VDD is not an optional
> for the controller. regulator_get_optional() is needed when you need to
> alter the behavior of the device/driver depending on the presence of an
> optional supply, whereas here it should work fine with a sub supply that
> will be created if you simply call devm_regulator_get_enable() and there
> is not regulator mentioned in DT/ACPI for the board.

Indeed, "optional" isn't correct here (I probably had the clock variant=20
in mind), a dummy regulator is fine.

BTW, I also have a patch in store that tries to "recover" the device=20
(using its reset when possible) if it isn't responding or if it causes=20
I2C errors. Took several weeks uptime for this to occur spontaneously on=20
our hardware, so I'll wait for this series so I can put that patch on=20
top of this one.

--=20
Mike Looijmans
System Expert

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