Date:   Thu, 23 Jul 2020 10:57:23 +0800
From:   Weiyi Lu <weiyi.lu@...iatek.com>
To:     Nicolas Boichat <drinkcat@...omium.org>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
        James Liao <jamesjj.liao@...iatek.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Wendell Lin <wendell.lin@...iatek.com>,
        Ikjoon Jang <ikjn@...omium.org>
Subject: Re: [PATCH 3/4] clk: mediatek: Add configurable enable control to
 mtk_pll_data

On Wed, 2020-07-22 at 16:51 +0800, Nicolas Boichat wrote:
> On Wed, Jul 22, 2020 at 2:50 PM Weiyi Lu <weiyi.lu@...iatek.com> wrote:
> >
> > In all MediaTek PLL design, bit 0 of CON0 register is always
> > the enable bit.
> > However, there's a special case of usbpll on MT8192.
> > The enable bit of usbpll is moved to bit 2 of other register.
> > Add configurable en_reg and base_en_bit for enable control or
> > using the default if without setting in pll data.
> >
> > Signed-off-by: Weiyi Lu <weiyi.lu@...iatek.com>
> > ---
> >  drivers/clk/mediatek/clk-mtk.h |  2 ++
> >  drivers/clk/mediatek/clk-pll.c | 26 ++++++++++++++++++++++----
> >  2 files changed, 24 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/clk/mediatek/clk-mtk.h b/drivers/clk/mediatek/clk-mtk.h
> > index c3d6756..8bb0b3d 100644
> > --- a/drivers/clk/mediatek/clk-mtk.h
> > +++ b/drivers/clk/mediatek/clk-mtk.h
> > @@ -233,6 +233,8 @@ struct mtk_pll_data {
> >         uint32_t pcw_chg_reg;
> >         const struct mtk_pll_div_table *div_table;
> >         const char *parent_name;
> > +       uint32_t en_reg;
> > +       uint8_t base_en_bit;
> >  };
> >
> >  void mtk_clk_register_plls(struct device_node *node,
> > diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> > index f440f2cd..b8ccd42 100644
> > --- a/drivers/clk/mediatek/clk-pll.c
> > +++ b/drivers/clk/mediatek/clk-pll.c
> > @@ -44,6 +44,7 @@ struct mtk_clk_pll {
> >         void __iomem    *tuner_en_addr;
> >         void __iomem    *pcw_addr;
> >         void __iomem    *pcw_chg_addr;
> > +       void __iomem    *en_addr;
> >         const struct mtk_pll_data *data;
> >  };
> >
> > @@ -56,7 +57,10 @@ static int mtk_pll_is_prepared(struct clk_hw *hw)
> >  {
> >         struct mtk_clk_pll *pll = to_mtk_clk_pll(hw);
> >
> > -       return (readl(pll->base_addr + REG_CON0) & CON0_BASE_EN) != 0;
> > +       if (pll->en_addr)
> > +               return (readl(pll->en_addr) & BIT(pll->data->base_en_bit)) != 0;
> > +       else
> > +               return (readl(pll->base_addr + REG_CON0) & CON0_BASE_EN) != 0;
> >  }
> >
> >  static unsigned long __mtk_pll_recalc_rate(struct mtk_clk_pll *pll, u32 fin,
> > @@ -251,6 +255,12 @@ static int mtk_pll_prepare(struct clk_hw *hw)
> >         r |= pll->data->en_mask;
> >         writel(r, pll->base_addr + REG_CON0);
> >
> 
> This is not a new change, but I'm wondering if the asymmetry is
> intentional here, that is, prepare sets bit pll->data->en_mask of
> REG_CON0; unprepare clears CON0_BASE_EN of REG_CON0.
> 
> With this patch, if pll->en_addr is set, you set both
> pll->data->en_mask _and_ pll->data->base_en_bit, and clear only
> pll->data->base_en_bit.
> 

Hi Nicolas,

AFAIK, the asymmetry was intentional.
en_mask is actually a combination of divider enable mask and the pll
enable bit(CON0_BASE_EN).
Even without my patch, it still sets divider enable mask and en_bit, and
only clears en_bit.
You could see the pll_data in clk-mt8192.c of patch [4/4]
Take mainpll as an example,
the enable mask of mainpll is 0xff000001, where 0xff000000 is the
divider enable mask and 0x1 is the en_bit

For usbpll in special case, usbpll doesn't have divider enable mask on
MT8192 so I give nothing(0x00000000) in the en_mask field.
However, the main reason why I don't skip setting the en_mask of MT8192
usbpll is that I'd just like to reserve the divider enable mask for any
special plls with divider enable mask in near future.

> > +       if (pll->en_addr) {
> > +               r = readl(pll->en_addr);
> > +               r |= BIT(pll->data->base_en_bit);
> > +               writel(r, pll->en_addr);
> > +       }
> > +
> >         __mtk_pll_tuner_enable(pll);
> >
> >         udelay(20);
> > @@ -277,9 +287,15 @@ static void mtk_pll_unprepare(struct clk_hw *hw)
> >
> >         __mtk_pll_tuner_disable(pll);
> >
> > -       r = readl(pll->base_addr + REG_CON0);
> > -       r &= ~CON0_BASE_EN;
> > -       writel(r, pll->base_addr + REG_CON0);
> > +       if (pll->en_addr) {
> > +               r = readl(pll->en_addr);
> > +               r &= ~BIT(pll->data->base_en_bit);
> > +               writel(r, pll->en_addr);
> > +       } else {
> > +               r = readl(pll->base_addr + REG_CON0);
> > +               r &= ~CON0_BASE_EN;
> > +               writel(r, pll->base_addr + REG_CON0);
> > +       }
> >
> >         r = readl(pll->pwr_addr) | CON0_ISO_EN;
> >         writel(r, pll->pwr_addr);
> > @@ -321,6 +337,8 @@ static struct clk *mtk_clk_register_pll(const struct mtk_pll_data *data,
> >                 pll->tuner_addr = base + data->tuner_reg;
> >         if (data->tuner_en_reg)
> >                 pll->tuner_en_addr = base + data->tuner_en_reg;
> > +       if (data->en_reg)
> > +               pll->en_addr = base + data->en_reg;
> 
> If the answer to my question above holds (asymmetry is not
> intentional), this patch/the code could be simplified a lot if you
> also added a pll->en_bit member, and, here, did this:
> 
> if (pll->en_reg) {
>    pll->en_addr = base + data->en_reg;
>    pll->end_bit = data->en_bit;
> } else {
>    pll->en_addr = pll->base_addr + REG_CON0;
>    pll->en_bit = CON0_BASE_EN;
> }
> 
> >         pll->hw.init = &init;
> >         pll->data = data;
> >
> > --
> > 1.8.1.1.dirty

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