linux-kernel - Re: [PATCH v3 03/12] clk: mediatek: add configurable pcwibits and fmin to mtk_pll

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Message-ID: <1549009333.22634.2.camel@mtksdaap41>
Date:   Fri, 1 Feb 2019 16:22:13 +0800
From:   Weiyi Lu <weiyi.lu@...iatek.com>
To:     Stephen Boyd <sboyd@...nel.org>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Rob Herring <robh@...nel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        James Liao <jamesjj.liao@...iatek.com>,
        Fan Chen <fan.chen@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
        <srv_heupstream@...iatek.com>, <stable@...r.kernel.org>,
        Owen Chen <owen.chen@...iatek.com>
Subject: Re: [PATCH v3 03/12] clk: mediatek: add configurable pcwibits and
 fmin to mtk_pll_data


On Fri, 2018-12-14 at 14:02 -0800, Stephen Boyd wrote:
> Quoting Weiyi Lu (2018-12-09 23:32:31)
> > diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> > index f0ff5f535c7e..81400601f107 100644
> > --- a/drivers/clk/mediatek/clk-pll.c
> > +++ b/drivers/clk/mediatek/clk-pll.c
> > @@ -69,11 +71,13 @@ static unsigned long __mtk_pll_recalc_rate(struct mtk_clk_pll *pll, u32 fin,
> >  {
> >         int pcwbits = pll->data->pcwbits;
> >         int pcwfbits;
> > +       int ibits;
> >         u64 vco;
> >         u8 c = 0;
> >  
> >         /* The fractional part of the PLL divider. */
> > -       pcwfbits = pcwbits > INTEGER_BITS ? pcwbits - INTEGER_BITS : 0;
> > +       ibits = pll->data->pcwibits ? pll->data->pcwibits : INTEGER_BITS;
> > +       pcwfbits = pcwbits > ibits ? pcwbits - ibits : 0;
> 
> This is practically unreadable. It should be changed to an if statement.
> 

OK, will be fixed in next version.

> >  
> >         vco = (u64)fin * pcw;
> >  
> > @@ -167,9 +171,10 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
> >  static void mtk_pll_calc_values(struct mtk_clk_pll *pll, u32 *pcw, u32 *postdiv,
> >                 u32 freq, u32 fin)
> >  {
> > -       unsigned long fmin = 1000 * MHZ;
> > +       unsigned long fmin = pll->data->fmin ? pll->data->fmin : (1000 * MHZ);
> >         const struct mtk_pll_div_table *div_table = pll->data->div_table;
> >         u64 _pcw;
> > +       int ibits;
> >         u32 val;
> >  
> >         if (freq > pll->data->fmax)
> > @@ -193,7 +198,8 @@ static void mtk_pll_calc_values(struct mtk_clk_pll *pll, u32 *pcw, u32 *postdiv,
> >         }
> >  
> >         /* _pcw = freq * postdiv / fin * 2^pcwfbits */
> > -       _pcw = ((u64)freq << val) << (pll->data->pcwbits - INTEGER_BITS);
> > +       ibits = pll->data->pcwibits ? pll->data->pcwibits : INTEGER_BITS;
> > +       _pcw = ((u64)freq << val) << (pll->data->pcwbits - ibits);
> 
> Similar comment. Readability is low here.

I thought these two lines here are clean enough. Just simple conditional
assignment and shift operation. I'd like to not to change it.

>