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Subject: Re: [PATCH v6 5/5]  mfd: max77541: Add ADI MAX77541/MAX77540 PMIC
 Support
From:   Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Mark Brown <broonie@kernel.org>,
        "Sahin, Okan" <Okan.Sahin@analog.com>, Lee Jones <lee@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
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        Cosmin Tanislav <demonsingur@gmail.com>,
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        "Bolboaca, Ramona" <Ramona.Bolboaca@analog.com>,
        ChiYuan Huang <cy_huang@richtek.com>,
        "Tilki, Ibrahim" <Ibrahim.Tilki@analog.com>,
        William Breathitt Gray <william.gray@linaro.org>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>
Date:   Tue, 28 Mar 2023 16:51:18 +0200
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On Tue, 2023-03-28 at 17:35 +0300, Andy Shevchenko wrote:
> On Tue, Mar 28, 2023 at 04:18:30PM +0200, Nuno S=C3=A1 wrote:
> > On Tue, 2023-03-28 at 14:46 +0100, Mark Brown wrote:
> > > On Tue, Mar 28, 2023 at 03:26:44PM +0200, Nuno S=C3=A1 wrote:
> > >=20
> > > > IIRC, regmap_read() is not really reentrant and it is used in
> > > > the
> > > > IIO
> > > > driver on the sysfs interface. So, yeah, I think you need the
> > > > regmap
> > > > lock and better just leave the config as is. Yes, the lock is
> > > > opt-
> > > > out
> > > > so let's not disable it :)
> > >=20
> > > All the regmap operations are fully thread safe.
> >=20
> > Even if 'config->disable_locking' is set? I think that is what's
> > being
> > discussed in here...
>=20
> In case the driver has its own lock to serialize IO how on earth the
> regmap
> lock is needed. That's what I asked the author of the driver. He told
> the code

Well, if the driver has it's own locking, then sure we do not need
regmap's lock...

> doesn't require the regmap lock, and I tend to believe the author.
> So, why to
> keep it?
>=20

However, if you look at the adc driver, I can see plain regmap_read()
calls without any "outside" locking.

- Nuno S=C3=A1