linux-kernel - Re: [PATCH v15 mfd 9/9] mfd: ocelot: add support for the vsc7512 chip via spi

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Message-ID: <CAHp75VeXtuR=CYyPE9VEE0+QoQ3hgVYCoSu4Yb8EycvChi86BQ@mail.gmail.com>
Date:   Wed, 3 Aug 2022 19:10:38 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Colin Foster <colin.foster@...advantage.com>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Terry Bowman <terry.bowman@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Wolfram Sang <wsa@...nel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>, katie.morris@...advantage.com
Subject: Re: [PATCH v15 mfd 9/9] mfd: ocelot: add support for the vsc7512 chip
 via spi

On Wed, Aug 3, 2022 at 5:56 PM Colin Foster
<colin.foster@...advantage.com> wrote:
> On Wed, Aug 03, 2022 at 01:45:04PM +0200, Andy Shevchenko wrote:
> > On Wed, Aug 3, 2022 at 7:48 AM Colin Foster
> > <colin.foster@...advantage.com> wrote:

...

> > > +       regmap_config.max_register = res->end - res->start;
> >
> > Hmm... First of all, resource_size() is for that (with - 1 to the
> > result). But don't you need to use stride in the calculations?
>
> DEFINE_RES_NAMED populates the resource .end with (_start) + (_size) - 1
> so I don't think resource_size is correct to use here.

Have you read what I put in parentheses? Basically it becomes very
well the same as a result, but in a cleaner manner (you calculate
resource size - 1 which will be exactly the last byte offset of the
register file), no?

> reg_stride gets handled at the top of regmap_read(), so I don't think
> that's really needed either.

Okay.

> For reference:
>
> #define VSC7512_DEVCPU_ORG_RES_START    0x71000000
> #define VSC7512_DEVCPU_ORG_RES_SIZE     0x38

Right, for 0x38 you supply 0x37, which is exactly resource_size() - 1.

> # cat range
> 0-34

-- 
With Best Regards,
Andy Shevchenko