linux-kernel - Re: [PATCH v3 5/5] usb: typec: tcpm/tcpci_maxim: deprecate WAR for setting charger mode

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Message-ID: <9f94993e-dd69-4c9e-b467-aad6031c83d4@google.com>
Date: Fri, 9 Jan 2026 18:16:57 -0800
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, André Draszik
 <andre.draszik@...aro.org>, Lee Jones <lee@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Badhri Jagan Sridharan <badhri@...gle.com>,
 Peter Griffin <peter.griffin@...aro.org>,
 Tudor Ambarus <tudor.ambarus@...aro.org>,
 Alim Akhtar <alim.akhtar@...sung.com>, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-samsung-soc@...r.kernel.org, RD Babiera <rdbabiera@...gle.com>,
 Kyle Tso <kyletso@...gle.com>
Subject: Re: [PATCH v3 5/5] usb: typec: tcpm/tcpci_maxim: deprecate WAR for
 setting charger mode

Hi Heikki,

Thanks for the review!

On 1/9/26 5:14 AM, Heikki Krogerus wrote:
> Hi,
>
>> +	if (source) {
>> +		if (!regulator_is_enabled(chip->vbus_reg))
>> +			ret = regulator_enable(chip->vbus_reg);
>> +	} else {
>> +		if (regulator_is_enabled(chip->vbus_reg))
>> +			ret = regulator_disable(chip->vbus_reg);
>> +	}
> It looks like you have to do one more round, so can drop the
> regulator_is_enabled() checks and just always enable/disable it
> unconditionally.
>
>         if (source)
> 		ret = regulator_enable(chip->vbus_reg);
> 	else
> 		ret = regulator_disable(chip->vbus_reg);

The regulator framework uses refcounting on the number of enables. If
the number of times regulator is disabled > enabled, a warning will be
thrown. Also, I don't want to call regulator_enable more than once for
the same refcounting reason (will have to call disable those many number
of times to actually disable).

> I don't think you need the check in any case, but if I've understood
> this correctly, you should not use that check when the regulator does
> not support that check because then the API claims it's always
> enabled. So I guess in that case "if (!regulator_is_enabled())" may
> not work as expected, and you may actually be left with a disabled
> regulator. This may not be a problem on current platforms, but who
> knows what happens in the future.

I don't think this should be an issue in the future as this driver is
specifically meant for max77759_tcpci device and should only be used
with max77759 charger (they both exist only in the same package). And
that the max77759_charger driver does implement the callback. However,
if you think that regulator_is_enabled() is unreliable, I could track
the state within the tcpci driver instead of calling
regulator_is_enabled() and call enable/disable regulator accordingly.

Let me know wdyt and I'll update the next revision accordingly.

BR,

Amit

>
> thanks,
>