linux-kernel - Re: [PATCH 03/13] mfd: pm8008: deassert reset on probe

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Date: Tue, 7 May 2024 17:15:36 +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 <quic_c_skakit@...cinc.com>,
	Stephen Boyd <swboyd@...omium.org>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH 03/13] mfd: pm8008: deassert reset on probe

On Mon, May 06, 2024 at 09:57:07PM +0300, Andy Shevchenko wrote:
> Mon, May 06, 2024 at 05:08:20PM +0200, Johan Hovold kirjoitti:
> > 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.
> 
> ...
> 
> > +	reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> > +	if (IS_ERR(reset))
> > +		return PTR_ERR(reset);
> 
> Shouldn't you wait a bit to make chip settle down?

Yeah, probably. I actually asserted reset here for a while (e.g. to
reset the address), but didn't have to use a post-reset delay then.

I'll see if I can find someone with access to a datasheet or maybe add
some small delay here anyway.

Johan