linux-kernel - Re: [PATCH v2 03/11] clk: mediatek: Disable tuner_en before change PLL rate

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Message-ID: <CAGp9LzqfgLa03p-bEOQaT2qtuOEqUL3e04nDS38TbZ2-2Ohauw@mail.gmail.com>
Date:   Tue, 27 Nov 2018 16:58:57 -0800
From:   Sean Wang <sean.wang@...nel.org>
To:     drinkcat@...omium.org
Cc:     weiyi.lu@...iatek.com, Matthias Brugger <matthias.bgg@...il.com>,
        sboyd@...eaurora.org, robh@...nel.org, jamesjj.liao@...iatek.com,
        srv_heupstream@...iatek.com, linux-kernel@...r.kernel.org,
        fan.chen@...iatek.com, linux-mediatek@...ts.infradead.org,
        owen.chen@...iatek.com, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 03/11] clk: mediatek: Disable tuner_en before change
 PLL rate

>
> On Wed, Nov 28, 2018 at 4:37 AM Sean Wang <sean.wang@...nel.org> wrote:
> >
> > Weiyi Lu <weiyi.lu@...iatek.com> 於 2018年11月26日 週一 下午7:45寫道：
> > >
> > > From: Owen Chen <owen.chen@...iatek.com>
> > >
> > > PLLs with tuner_en bit, such as APLL1, need to disable
> > > tuner_en before apply new frequency settings, or the new frequency
> > > settings (pcw) will not be applied.
> > > The tuner_en bit will be disabled during changing PLL rate
> > > and be restored after new settings applied.
> >
> > It looks like a bug fix. If so, you should add a fixes tag and even cc
> > stable tree
> >
> > >
> > > Signed-off-by: Owen Chen <owen.chen@...iatek.com>
> > > ---
> > >  drivers/clk/mediatek/clk-pll.c | 33 +++++++++++++++++++++++++++++++--
> > >  1 file changed, 31 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> > > index 1db161aced31..81400601f107 100644
> > > --- a/drivers/clk/mediatek/clk-pll.c
> > > +++ b/drivers/clk/mediatek/clk-pll.c
> > > @@ -27,7 +27,7 @@
> > >  #define CON0_BASE_EN           BIT(0)
> > >  #define CON0_PWR_ON            BIT(0)
> > >  #define CON0_ISO_EN            BIT(1)
> > > -#define CON0_PCW_CHG           BIT(31)
> > > +#define CON1_PCW_CHG           BIT(31)
> >
> > it seems like an unnecessary change
>
> Below, you have:
> con1 |= CON1_PCW_CHG;
>
> Presumably PCW_CHG is on BIT(31) of CON1(?), so I think this is a good
> change. Maybe this needs to be a separate patch, though?
>

Sure, for me it's not easily understood why the change is necessary
from the description. If it's really another fixup, it should be moved
to a separate patch or add more explanations about that in the same
patch.

> > >
> > >  #define AUDPLL_TUNER_EN                BIT(31)
> > >
> > > @@ -97,9 +97,31 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
> > >  {
> > >         u32 con1, val;
> > >         int pll_en;
> > > +       u32 tuner_en = 0;
> > > +       u32 tuner_en_mask;
> > > +       void __iomem *tuner_en_addr = NULL;
> > >
> > >         pll_en = readl(pll->base_addr + REG_CON0) & CON0_BASE_EN;
> > >
> > > +       /* disable tuner */
> >
> > similar code pieces are ready on mtk_pll_[un]prepare. maybe we can add
> > common tuner operations for them to reuse.
> >
> > > +       if (pll->tuner_en_addr) {
> > > +               tuner_en_addr = pll->tuner_en_addr;
> > > +               tuner_en_mask = BIT(pll->data->tuner_en_bit);
> > > +       } else if (pll->tuner_addr) {
> > > +               tuner_en_addr = pll->tuner_addr;
> > > +               tuner_en_mask = AUDPLL_TUNER_EN;
> > > +       }
> > > +
> > > +       if (tuner_en_addr) {
> > > +               val = readl(tuner_en_addr);
> > > +               tuner_en = val & tuner_en_mask;
> > > +
> > > +               if (tuner_en) {
> > > +                       val &= ~tuner_en_mask;
> > > +                       writel(val, tuner_en_addr);
> > > +               }
> > > +       }
> > > +
> > >         /* set postdiv */
> > >         val = readl(pll->pd_addr);
> > >         val &= ~(POSTDIV_MASK << pll->data->pd_shift);
> > > @@ -120,12 +142,19 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
> > >         con1 = readl(pll->base_addr + REG_CON1);
> > >
> > >         if (pll_en)
> > > -               con1 |= CON0_PCW_CHG;
> > > +               con1 |= CON1_PCW_CHG;
> > >
> > >         writel(con1, pll->base_addr + REG_CON1);
> > >         if (pll->tuner_addr)
> > >                 writel(con1 + 1, pll->tuner_addr);
> > >
> > > +       /* restore tuner_en */
> > > +       if (tuner_en_addr && tuner_en) {
> >
> > if (tuner_en) is sufficient
> >
> > > +               val = readl(tuner_en_addr);
> > > +               val |= tuner_en_mask;
> > > +               writel(val, tuner_en_addr);
> > > +       }
> > > +
> > >         if (pll_en)
> > >                 udelay(20);
> > >  }
> > > --
> > > 2.18.0
> > >
> > >
> > > _______________________________________________
> > > Linux-mediatek mailing list
> > > Linux-mediatek@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-mediatek

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