Re: [PATCH v5 2/5] clk: meson: add support for A1 PLL clock ops

[Jian Hu]

Hi Martin

Thanks for your review

On 2019/12/28 0:53, Martin Blumenstingl wrote:
> Hi Jian,
>
> On Fri, Dec 27, 2019 at 10:46 AM Jian Hu <jian.hu@xxxxxxxxxxx> wrote:
> [...]
> > @@ -294,9 +298,12 @@ static int meson_clk_pll_is_enabled(struct clk_hw *hw)
> >   {
> >          struct clk_regmap *clk = to_clk_regmap(hw);
> >          struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
> > +       int ret = 0;
> >
> > -       if (meson_parm_read(clk->map, &pll->rst) ||
> > -           !meson_parm_read(clk->map, &pll->en) ||
> > +       if (MESON_PARM_APPLICABLE(&pll->rst))
> > +               ret = meson_parm_read(clk->map, &pll->rst);
> > +
> > +       if (ret || !meson_parm_read(clk->map, &pll->en) ||
> >              !meson_parm_read(clk->map, &pll->l))
> >                  return 0;
> I had to read this part twice to understand what it's doing because I
> misunderstood what "ret" is used for (I thought that some "return ret"
> is missing)
> my proposal to make it easier to read:
> ...
> if (MESON_PARM_APPLICABLE(&pll->rst) &&
>      meson_parm_read(clk->map, &pll->rst))
>    return 0;
>
> if (!meson_parm_read(clk->map, &pll->en) ||
>      !meson_parm_read(clk->map, &pll->l))
>                   return 0;
> ...
>
> please let me know what you think about this
I was intended to use 'ret' to store the return value of pll->rst.

If pll->rst exists, it will get it. Otherwise, the ret will be zero.

Your proposal is a good way for it. I will use it.
> > @@ -321,6 +328,23 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
> >          /* do nothing if the PLL is already enabled */
> >          if (clk_hw_is_enabled(hw))
> >                  return 0;
> > +       /*
> > +        * Compared with the previous SoCs, self-adaption module current
> > +        * is newly added for A1, keep the new power-on sequence to enable the
> > +        * PLL.
> > +        */
> > +       if (MESON_PARM_APPLICABLE(&pll->current_en)) {
> > +               /* Enable the pll */
> > +               meson_parm_write(clk->map, &pll->en, 1);
> > +               udelay(10);
> > +               /* Enable the pll self-adaption module current */
> > +               meson_parm_write(clk->map, &pll->current_en, 1);
> > +               udelay(40);
> > +               /* Enable lock detect module */
> > +               meson_parm_write(clk->map, &pll->l_detect, 1);
> > +               meson_parm_write(clk->map, &pll->l_detect, 0);
> > +               goto out;
> > +       }
> in all other functions you are skipping the pll->rst register by
> checking for MESON_PARM_APPLICABLE(&pll->rst)
> I like that because it's a pattern which is easy to follow
>
> do you think we can make this part consistent with that?
> I'm thinking of something like this (not compile-tested and I dropped
> all comments, just so you get the idea):
It is a good idea. I will test it.
> ...
> if (MESON_PARM_APPLICABLE(&pll->rst)
>    meson_parm_write(clk->map, &pll->rst, 1);
>
> meson_parm_write(clk->map, &pll->en, 1);
>
> if (MESON_PARM_APPLICABLE(&pll->rst))
>    meson_parm_write(clk->map, &pll->rst, 0);
>
> if (MESON_PARM_APPLICABLE(&pll->current_en))
>    meson_parm_write(clk->map, &pll->current_en, 1);
>
> if (MESON_PARM_APPLICABLE(&pll->l_detect)) {
>    meson_parm_write(clk->map, &pll->l_detect, 1);
>    meson_parm_write(clk->map, &pll->l_detect, 0);
> }
>
> if (meson_clk_pll_wait_lock(hw))
> ...
>
> I see two (and a half) benefits here:
> - if there's a PLL with neither the pll->current_en nor the pll->rst
> registers then you get support for this implementation for free
> - the if (MESON_PARM_APPLICABLE(...)) pattern is already used in the
> driver, but only for one register (in your example when
> MESON_PARM_APPLICABLE(&pll->current_en) exists you also modify the
> pll->l_detect register, which I did not expect)
> - only counts half: no use of "goto", which in my opinion makes it
> very easy to read (just read from top to bottom, checking each "if")
I see, I will verify it.
> Martin
>
> .