linux-kernel - Re: [PATCH v2 03/14] mfd: pm8008: deassert reset on probe

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Date: Thu, 30 May 2024 10:51:27 +0200
From: Johan Hovold <johan@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Johan Hovold <johan+linaro@...nel.org>, Lee Jones <lee@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Das Srinagesh <quic_gurus@...cinc.com>,
	Satya Priya Kakitapalli <quic_skakitap@...cinc.com>,
	Stephen Boyd <swboyd@...omium.org>,
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH v2 03/14] mfd: pm8008: deassert reset on probe

On Thu, May 30, 2024 at 11:34:55AM +0300, Andy Shevchenko wrote:
> On Thu, May 30, 2024 at 11:08 AM Johan Hovold <johan@...nel.org> wrote:
> > On Wed, May 29, 2024 at 10:45:40PM +0300, Andy Shevchenko wrote:
> > > On Wed, May 29, 2024 at 7:30 PM Johan Hovold <johan+linaro@...nel.org> wrote:
> > > >
> > > > Request and deassert any (optional) reset gpio during probe in case it
> > > > has been left asserted by the boot firmware.
> > > >
> > > > Note the reset line is not asserted to avoid reverting to the default
> > > > I2C address in case the firmware has configured an alternate address.
> 
> ...
> 
> > > > +       /*
> > > > +        * The PMIC does not appear to require a post-reset delay, but wait
> > > > +        * for a millisecond for now anyway.
> > > > +        */
> > >
> > > > +       usleep_range(1000, 2000);
> > >
> > > fsleep() ?
> >
> > No, I'd only use fsleep() when the argument is variable.
> 
> Okay, this is basically the same issue as with use of dev_err_probe()
> with known errors. fsleep() hides the choice between let's say
> msleep() / usleep_range() / udelay() from the caller. This, in
> particular, might allow shifting constraints if the timer core is
> changed or becomes more granular. It's independent to the variable or
> constant parameter(s). Whatever, I'm not going to insist.

I prefer that developers are aware of what they are doing and understand
the difference between, say, usleep_range() and udelay(), instead of
hiding things away in obscure helper functions.

Johan