linux-kernel - Re: [PATCH v2 5/7] mfd: Add RTL8231 core device

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Message-ID: <33eb043f2ef9d81bbe26876a1c73859f56a8abd9.camel@svanheule.net>
Date:   Mon, 24 May 2021 09:50:02 +0200
From:   Sander Vanheule <sander@...nheule.net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 5/7] mfd: Add RTL8231 core device

Hi Andy,

I forgot to address one of your questions, so here's a short follow up.

On Tue, 2021-05-18 at 00:18 +0300, Andy Shevchenko wrote:
> On Mon, May 17, 2021 at 10:28 PM Sander Vanheule <sander@...nheule.net> wrote:
> > +       err = regmap_read(map, RTL8231_REG_FUNC1, &v);
> 
> > +       ready_code = FIELD_GET(RTL8231_FUNC1_READY_CODE_MASK, v);
> 
> If we got an error why we need a read_core, what for?

The chip has a static 5-bit field in register 0x01, called READY_CODE according
to the datasheet. If a device is present, and a read from register 0x01
succeeds, I still check that this field has the correct value. For the RTL8231,
it should return 0x37. If this isn't the case, I assume this isn't an RTL8231,
so the driver probe stops and returns an error value.

Best,
Sander