linux-kernel - Re: [PATCH v3 2/2] thermal: uniphier: add UniPhier thermal driver

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Message-Id: <20170706094205.1DAF.4A936039@socionext.com>
Date:   Thu, 06 Jul 2017 09:42:06 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     rui.zhang@...el.com, Eduardo Valentin <edubezval@...il.com>,
        linux-pm@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH v3 2/2] thermal: uniphier: add UniPhier thermal driver

On Wed, 5 Jul 2017 21:27:57 +0900 <yamada.masahiro@...ionext.com> wrote:

> 2017-07-05 21:20 GMT+09:00 Masahiro Yamada <yamada.masahiro@...ionext.com>:
> > 2017-07-05 20:50 GMT+09:00 Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>:
> >
> >> +
> >> +#define TMOD                           0x0928
> >> +#define TMOD_MASK                      GENMASK(9, 0)
> >> +
> >  [ snip ]
> >> +
> >> +       /*
> >> +        * The bit[8:0] of TMOD register represents 2's complement value
> >> +        * of temperature in Celsius. Since bit8 of TMOD shows a sign bit,
> >> +        * 32bit temperature value is obtained by sign extension.
> >> +        */
> >
> >
> > Apparently, this comment does not match your code:
> >
> >      #define TMOD_MASK                      GENMASK(9, 0)
> >
> >
> > TMOD_MASK is indicating bit[9:0].
> >
> >
> >
> > Digging into the patch history, now I understood what happened.
> >
> >
> >
> > In v1, you described
> > #define TMOD_MASK         0x1ff
> >
> > This was correct.
> >
> >
> > In v2, you converted it into
> > #define TMOD_MASK          GENMASK(9, 0)
> >
> > This was misconversion.  It should be GENMASK(8, 0)
> >
> >
> >
> > Anyway, TMOD_MASK is not used any more.

That's true.
TMOD_MASK in v2/v3 is wrong, and not used no longer.

> >> +       *out_temp = sign_extend32(temp, 8) * 1000;
> >
> >
> > Why magic number here?
> >
> >    /* MSB of the TMOD field is a sign bit */
> >    *out_temp = sign_extend32(temp, TMOD_WIDTH) * 1000;
> 
> No.    sign_extend32(temp, TMOD_WIDTH - 1) or
>        sign_extend32(temp, TMOD_MSB)  or whatever.

I see. I'll replace with the macro.

Best Regards,
Kunihiko Hayashi