linux-kernel - Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC

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Message-ID: <CAHp75VfPozwBPpuP9HadSc2GVm7tbPpMxg+AtACZa9jzVGGT-Q@mail.gmail.com>
Date:   Thu, 26 Jul 2018 16:44:08 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Keiji Hayashibara <hayashibara.keiji@...ionext.com>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Yamada, Masahiro/山田 真弘 
        <yamada.masahiro@...ionext.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hayashi, Kunihiko/林 邦彦 
        <hayashi.kunihiko@...ionext.com>
Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC

On Thu, Jul 26, 2018 at 12:38 PM, Keiji Hayashibara
<hayashibara.keiji@...ionext.com> wrote:

>> > +       /* check if requested speed is too small */
>> > +       if (ckrat > SSI_MAX_CLK_DIVIDER)
>>
>> > +               return -EINVAL;
>>
>> So, does this critical?
>
> If set the value to SSI_MAX_CLK_DIVIDER, the clock frequency will be set high.
> I don't change it to high frequency, and it is daringly an error.
> On the other hand, when changing to low frequency, I will change it automatically.

No. My point is, if somehow user asks for that condition to be
happened you bail out, while when using clamp_val() you may continue
to work at maximum limit, though issue warning to user, for example.

>> > +
>> > +       if (ckrat < SSI_MIN_CLK_DIVIDER)
>> > +               ckrat = SSI_MIN_CLK_DIVIDER;
>>
>> clamp_val()  / max() ?
>
> I will modify it to use max().

See above.

-- 
With Best Regards,
Andy Shevchenko