linux-kernel - Re: [PATCH 2/3] iio: pressure: Honeywell mpr pressure sensor

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Message-ID: <20230408122932.61d2bff0@jic23-huawei>
Date:   Sat, 8 Apr 2023 12:29:32 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andreas Klinger <ak@...klinger.de>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Angel Iglesias <ang.iglesiasg@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] iio: pressure: Honeywell mpr pressure sensor

On Thu, 6 Apr 2023 21:43:57 +0200
Andreas Klinger <ak@...klinger.de> wrote:

> Hi Jonathan,
> 
> thanks for the extensive review. Most of it is clear but one questions remain.
> See below.
> 
> Jonathan Cameron <jic23@...nel.org> schrieb am Sa, 01. Apr 18:57:
> > > +static void mpr_reset(struct mpr_data *data)
> > > +{
> > > +	if (data->gpiod_reset) {
> > > +		gpiod_set_value(data->gpiod_reset, 0);
> > > +		udelay(10);
> > > +		gpiod_set_value(data->gpiod_reset, 1);
> > > +	}  
> > 
> > If there isn't a reset signal, I'd like to see an attempt at least to write
> > all configuration registers to a known value (same as the one you'd
> > get after reset).    
> 
> There is no configuration register in the sensor I could write to. But maybe I
> didn't comprehend your point.

Ah. Devices is even simpler than I was anticipating. Which makes me wonder.
What does the reset actually do?

I checked the datasheet and reason to bother with this is about powersupplies
that don't come up fast enough.  Fair enough. If someone hasn't wired
the reset I guess they are happy that the power on reset will work.
(4.0 Power support requirement) 

Jonathan

> 
> Andreas
>