Re: [PATCH v7 2/5] clk: meson: add support for A1 PLL clock ops

Jerome Brunet
2020-02-04T10:24:17Z

On Mon 20 Jan 2020 at 04:49, Jian Hu <jian.hu@amlogic.com> wrote:

> Compared with the previous SoCs, self-adaption current module
> is newly added for A1, and there is no reset parm except the
> fixed pll. In A1 PLL, the PLL enable sequence is different, using
> the new power-on sequence to enable the PLL.

Things are getting clearer thanks to Martin's suggestions and I can
understand what your driver is doing now

However, I still have a problem with the fact that 2 different pll types
are getting intertwined in this driver. Parameters mandatory to one is
made optional to the other. Nothing clearly shows which needs what and
the combinatorial are quickly growing.

Apparently the only real difference is in enable/disable, So I would
prefer if the a1 had dedicated function for these ops.

I suppose you'll have to submit clk_hw_enable() and clk_hw_disable()
to the framework to call the appropriate ops dependind on the SoC.

>
> Signed-off-by: Jian Hu <jian.hu@amlogic.com>
> Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> ---
> drivers/clk/meson/clk-pll.c | 47 +++++++++++++++++++++++++++++++------
> drivers/clk/meson/clk-pll.h | 2 ++
> 2 files changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clk/meson/clk-pll.c b/drivers/clk/meson/clk-pll.c
> index ddb1e5634739..10926291440f 100644
> --- a/drivers/clk/meson/clk-pll.c
> +++ b/drivers/clk/meson/clk-pll.c
> @@ -283,10 +283,14 @@ static void meson_clk_pll_init(struct clk_hw *hw)
> struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
>
> if (pll->init_count) {
> - meson_parm_write(clk->map, &pll->rst, 1);
> + if (MESON_PARM_APPLICABLE(&pll->rst))
> + meson_parm_write(clk->map, &pll->rst, 1);
> +

replace by
enabled = clk_hw_is_enabled(hw)
if (enabled)
clk_hw_disable(hw)

> regmap_multi_reg_write(clk->map, pll->init_regs,
> pll->init_count);
> - meson_parm_write(clk->map, &pll->rst, 0);
> +
> + if (MESON_PARM_APPLICABLE(&pll->rst))
> + meson_parm_write(clk->map, &pll->rst, 0);

/* restore if necessary */
if (enabled)
clk_hw_enable(hw)

> }
> }
>
> @@ -295,8 +299,11 @@ 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);
>
> - if (meson_parm_read(clk->map, &pll->rst) ||
> - !meson_parm_read(clk->map, &pll->en) ||
> + 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;

I suppose the pll can't be locked if it was in reset, so we could drop
the check on `rst` entirely to simplify the function

>
> @@ -323,13 +330,34 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
> return 0;
>
> /* Make sure the pll is in reset */
> - meson_parm_write(clk->map, &pll->rst, 1);
> + if (MESON_PARM_APPLICABLE(&pll->rst))
> + meson_parm_write(clk->map, &pll->rst, 1);
>
> /* Enable the pll */
> meson_parm_write(clk->map, &pll->en, 1);
>
> /* Take the pll out reset */
> - meson_parm_write(clk->map, &pll->rst, 0);
> + if (MESON_PARM_APPLICABLE(&pll->rst))
> + meson_parm_write(clk->map, &pll->rst, 0);
> +
> + /*
> + * Compared with the previous SoCs, self-adaption current module
> + * is newly added for A1, keep the new power-on sequence to enable the
> + * PLL. The sequence is:
> + * 1. enable the pll, delay for 10us
> + * 2. enable the pll self-adaption current module, delay for 40us
> + * 3. enable the lock detect module
> + */
> + if (MESON_PARM_APPLICABLE(&pll->current_en)) {
> + udelay(10);
> + meson_parm_write(clk->map, &pll->current_en, 1);
> + udelay(40);
> + };
> +
> + 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))
> return -EIO;
> @@ -343,10 +371,15 @@ static void meson_clk_pll_disable(struct clk_hw *hw)
> struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
>
> /* Put the pll is in reset */
> - meson_parm_write(clk->map, &pll->rst, 1);
> + if (MESON_PARM_APPLICABLE(&pll->rst))
> + meson_parm_write(clk->map, &pll->rst, 1);
>
> /* Disable the pll */
> meson_parm_write(clk->map, &pll->en, 0);
> +
> + /* Disable PLL internal self-adaption current module */
> + if (MESON_PARM_APPLICABLE(&pll->current_en))
> + meson_parm_write(clk->map, &pll->current_en, 0);
> }

With the above clarified, it should be easy to properly split the
functions between the legacy type and the a1 type.

You'll need to update meson_clk_pll_set_rate() to call
- clk_hw_is_enabled()
- clk_hw_enable() and clk_hw_disable() (again, you'll need to add
those in the framework first)

>
> static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
> diff --git a/drivers/clk/meson/clk-pll.h b/drivers/clk/meson/clk-pll.h
> index 367efd0f6410..a2228c0fdce5 100644
> --- a/drivers/clk/meson/clk-pll.h
> +++ b/drivers/clk/meson/clk-pll.h
> @@ -36,6 +36,8 @@ struct meson_clk_pll_data {
> struct parm frac;
> struct parm l;
> struct parm rst;
> + struct parm current_en;
> + struct parm l_detect;
> const struct reg_sequence *init_regs;
> unsigned int init_count;
> const struct pll_params_table *table;