linux-kernel - Re: [RFC PATCH 1/2] net: wireless: Add Nordic nRF70 series Wi-Fi driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aAo5leoKBdCUvImP@pengutronix.de>
Date: Thu, 24 Apr 2025 15:16:05 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Artur Rojek <artur@...clusive.pl>
Cc: Johannes Berg <johannes@...solutions.net>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-wireless@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jakub Klama <jakub@...clusive.pl>,
	Wojciech Kloska <wojciech@...clusive.pl>,
	Ulf Axelsson <ulf.axelsson@...dicsemi.no>
Subject: Re: [RFC PATCH 1/2] net: wireless: Add Nordic nRF70 series Wi-Fi
 driver

On Fri, Apr 18, 2025 at 02:46:34PM +0200, Artur Rojek wrote:
> Hi Sascha,
> 
> thanks for the review, reply inline.
> 
 >
> > > +
> > > +     ret = gpiod_direction_output(priv->buck_en, 0);
> > > +     if (ret) {
> > > +             dev_err(dev, "Unable to set buck_en direction\n");
> > > +             return -EIO;
> > > +     }
> >
> > Should this "bucken" GPIO rather be a regulator?
> >
> > Is this really mandatory? It sounds like it could be hardwired to some
> > fixed voltage.
> 
> Take this with a grain of salt, as I am not a hardware designer.
> Nordic's Product Specification document [1] stipulates that BUCKEN line
> controls the PWR IP core. In order to start the IC, a power up sequence
> is required: first the various power supply lines, then BUCKEN, then
> IOVDD signal. Similar with a power down sequence.
> To me, this reads that BUCKEN cannot be simply wired to some fixed
> voltage and needs some sort of state control. Additionally, it is
> the (only?) way for the software to reset the IC and put it into a known
> state during probe, or after a hang.
> At least for the second case, the driver needs some sort of power
> control, whether it's directly the BUCKEN line, or some other circuit
> that in turn flicks the BUCKEN. I could rename it to 'vpwr-supply' if
> that makes things more transparent. I would risk saying that it makes
> it mandatory.
> 
> PS. The annoying part about the regulator API is that it reference
> counts its usage, and as such regulator_disable() cannot be called
> without a prior call to regulator_enable(). So to power-cycle the IC via
> the BUCKEN line, I will need to do the following sequence:
> regulator_enable() -> regulator_disable() -> regulator_enable()
> But I can live with that ;)

Ok, With this explanation I think it's best to use it as GPIO like you
did. It just sounded like the regulator API would fit here, hence the
question.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |