linux-kernel - Re: [RFC PATCH] spi: add driver for the SiFive SPI controller

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Message-ID: <20181113223822.GN2089@sirena.org.uk>
Date:   Tue, 13 Nov 2018 14:38:22 -0800
From:   Mark Brown <broonie@...nel.org>
To:     Emil Renner Berthing <kernel@...il.dk>
Cc:     linux-spi@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...ive.com>, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] spi: add driver for the SiFive SPI controller

On Tue, Nov 13, 2018 at 08:48:43PM +0100, Emil Renner Berthing wrote:
> On Tue, 13 Nov 2018 at 19:35, Mark Brown <broonie@...nel.org> wrote:
> > On Mon, Nov 12, 2018 at 03:27:36PM +0100, Emil Renner Berthing wrote:

> > > I know the discussions about the sifive devicetree compatible
> > > strings haven't come to a conclusion, so I'm sending this as
> > > an RFC to get some feedback on the rest of the code.

> > I've not seen any of these discussions or earlier versions of this
> > driver so I've no idea what's going on here :(

> No, sorry. This has been discussed on linux-riscv for other drivers
> like the uart. See my last answer.

> > > +Optional properties:
> > > +- sifive,fifo-depth          : Depth of hardware queues; defaults to 8
> > > +- sifive,max-bits-per-word   : Maximum bits per word; defaults to 8

> > If the hardware isn't fixed yet making these enumerable from the
> > hardware would be good...

> Agreed, but unfortunately this is already in the FU540-C000 chip on
> the HiFive Unleashed board sold by SiFive.

Pick an unused register you can read safely and define that value to the
default :)

> > > +/* for consistency we need this symbol */
> > > +#ifdef REG_FMT
> > > +#undef REG_FMT
> > > +#endif

> > We do?  For consistency with what?

> Below all the register offsets are defined as
> REG_<register name>. This is is a pattern I
> copied from other drivers, but here we have a
> register called "fmt" - hence REG_FMT.
> If you have a better pattern that doesn't clash
> with REG_FMT please let me know.

You shouldn't be using such generic names for your internal identifiers,
add a prefix to everything.

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