linux-kernel - Re: [PATCH 14/15] drivers: thermal: tsens: Create function to return sign-extended temperature

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Date:   Tue, 20 Aug 2019 02:21:28 +0530
From:   Amit Kucheria <amit.kucheria@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 14/15] drivers: thermal: tsens: Create function to return
 sign-extended temperature

On Sat, Aug 17, 2019 at 9:46 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Amit Kucheria (2019-07-25 15:18:49)
> > diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c
> > index 7ab2e740a1da..13a875b99094 100644
> > --- a/drivers/thermal/qcom/tsens-common.c
> > +++ b/drivers/thermal/qcom/tsens-common.c
> > @@ -84,13 +84,35 @@ static inline int code_to_degc(u32 adc_code, const struct tsens_sensor *s)
> >         return degc;
> >  }
> >
> > +/**
> > + * tsens_hw_to_mC - Return properly sign extended temperature in mCelsius,
>
> Can you make this proper kernel-doc? Describe the arguments and have a
> "Return:" section.

Will fix.

> > + * whether in ADC code or deciCelsius depending on IP version.
> > + * This function handles the different widths of the signed integer across IPs.
> > + */
> > +static int tsens_hw_to_mC(char *str, struct tsens_sensor *s, int field, int temp)
> > +{
> > +       struct tsens_priv *priv = s->priv;
> > +       u32 mask;
> > +
> > +       if (priv->feat->adc) {
> > +               /* Convert temperature from ADC code to milliCelsius */
> > +               return code_to_degc(temp, s) * 1000;
> > +       } else {
>
> Please deindent and drop the else because there's a return above.

Will fix.


> > +               mask = GENMASK(priv->fields[field].msb,
> > +                              priv->fields[field].lsb) >> priv->fields[field].lsb;
>
> Why is the mask generated, shifted right, sent into fls(), and then
> passed to sign_extend32? Shoudln't it be something like
>
>         sign_extend32(temp, priv->fields[field].msg - priv->fiels[field].lsb - 1)

Yes, that should work and greatly simply the function. Will fix.

> > +               dev_dbg(priv->dev, "%s: mask: %d\n", str, fls(mask));
> > +               /* Convert temperature from deciCelsius to milliCelsius */
> > +               return sign_extend32(temp, fls(mask) - 1) * 100;
> > +       }
> > +}
> > +
> > @@ -112,15 +134,7 @@ int get_temp_tsens_valid(struct tsens_sensor *s, int *temp)
> >         if (ret)
> >                 return ret;
> >
> > -       if (priv->feat->adc) {
> > -               /* Convert temperature from ADC code to milliCelsius */
> > -               *temp = code_to_degc(last_temp, s) * 1000;
> > -       } else {
> > -               mask = GENMASK(priv->fields[LAST_TEMP_0].msb,
> > -                              priv->fields[LAST_TEMP_0].lsb);
> > -               /* Convert temperature from deciCelsius to milliCelsius */
> > -               *temp = sign_extend32(last_temp, fls(mask) - 1) * 100;
>
> Oh the code is copied. Seems really complicated still.
>
> > -       }
> > +       *temp = tsens_hw_to_mC("get_temp", s, LAST_TEMP_0, last_temp);