netdev - Re: [PATCH 2/2] net: macb: Add support for SiFive FU540-C000

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Message-ID: <20190524134847.GF2979@lunn.ch>
Date:   Fri, 24 May 2019 15:48:47 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Yash Shah <yash.shah@...ive.com>
Cc:     mark.rutland@....com, devicetree@...r.kernel.org,
        aou@...s.berkeley.edu, netdev@...r.kernel.org,
        Palmer Dabbelt <palmer@...ive.com>,
        linux-kernel@...r.kernel.org, nicolas.ferre@...rochip.com,
        Sachin Ghadi <sachin.ghadi@...ive.com>, robh+dt@...nel.org,
        Paul Walmsley <paul.walmsley@...ive.com>, ynezz@...e.cz,
        linux-riscv@...ts.infradead.org, davem@...emloft.net
Subject: Re: [PATCH 2/2] net: macb: Add support for SiFive FU540-C000

On Fri, May 24, 2019 at 10:22:06AM +0530, Yash Shah wrote:
> On Thu, May 23, 2019 at 8:24 PM Andrew Lunn <andrew@...n.ch> wrote:
> >
> > > +static int fu540_macb_tx_set_rate(struct clk_hw *hw, unsigned long rate,
> > > +                               unsigned long parent_rate)
> > > +{
> > > +     rate = fu540_macb_tx_round_rate(hw, rate, &parent_rate);
> > > +     iowrite32(rate != 125000000, mgmt->reg);
> >
> > That looks odd. Writing the result of a comparison to a register?
> 
> The idea was to write "1" to the register if the value of rate is
> anything else than 125000000.

I'm not a language lawyer. Is it guaranteed that an expression like
this returns 1? Any value !0 is true, so maybe it actually returns 42?

> To make it easier to read, I will change this to below:
>     - iowrite32(rate != 125000000, mgmt->reg);
>     + if (rate != 125000000)
>     +     iowrite32(1, mgmt->reg);
>     + else
>     +     iowrite32(0, mgmt->reg);
> 
> Hope that's fine. Thanks for your comment

Yes, that is good.

     Andrew