Re: [PATCH v4 02/27] clk: mediatek: clk-pll: Add ops for PLLs using set/clr regs and FENC

[Laura Nao <laura.nao@collabora.com>]

Hi Chen-Yu,

On 8/15/25 05:18, Chen-Yu Tsai wrote:
> On Tue, Aug 5, 2025 at 10:55 PM Laura Nao <laura.nao@collabora.com> wrote:
>>
>> MT8196 uses a combination of set/clr registers to control the PLL
>> enable state, along with a FENC bit to check the preparation status.
>> Add new set of PLL clock operations with support for set/clr enable and
>> FENC status logic.
>>
>> Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
>> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
>> Signed-off-by: Laura Nao <laura.nao@collabora.com>
>> ---
>>  drivers/clk/mediatek/clk-pll.c | 42 +++++++++++++++++++++++++++++++++-
>>  drivers/clk/mediatek/clk-pll.h |  5 ++++
>>  2 files changed, 46 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
>> index 49ca25dd5418..8f46de77f42d 100644
>> --- a/drivers/clk/mediatek/clk-pll.c
>> +++ b/drivers/clk/mediatek/clk-pll.c
>> @@ -37,6 +37,13 @@ int mtk_pll_is_prepared(struct clk_hw *hw)
>>         return (readl(pll->en_addr) & BIT(pll->data->pll_en_bit)) != 0;
>>  }
>>
>> +static int mtk_pll_fenc_is_prepared(struct clk_hw *hw)
>> +{
>> +       struct mtk_clk_pll *pll = to_mtk_clk_pll(hw);
>> +
>> +       return readl(pll->fenc_addr) & pll->fenc_mask;
>
> Nits:
>
> I'd do a double-negate (!!) just to indicate that we only care about
> true or false.
>
> Also, why do we need to store fenc_mask instead of just shifting the bit
> here? Same goes for the register address. |pll| has the base address.
> Why do we need to pre-calculate it?
>
> The code is OK; it just seems a bit wasteful on memory.
>

Thanks for the heads up - since these are only used here for now, I
agree they’re not really adding value. I’ll drop fenc_mask and fenc_addr
in the next revision.

Best,

Laura

> Either way, this is
>
> Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
>
>> +}
>> +
>>  static unsigned long __mtk_pll_recalc_rate(struct mtk_clk_pll *pll, u32 fin,
>>                 u32 pcw, int postdiv)
>>  {
>> @@ -274,6 +281,25 @@ void mtk_pll_unprepare(struct clk_hw *hw)
>>         writel(r, pll->pwr_addr);
>>  }
>>
>> +static int mtk_pll_prepare_setclr(struct clk_hw *hw)
>> +{
>> +       struct mtk_clk_pll *pll = to_mtk_clk_pll(hw);
>> +
>> +       writel(BIT(pll->data->pll_en_bit), pll->en_set_addr);
>> +
>> +       /* Wait 20us after enable for the PLL to stabilize */
>> +       udelay(20);
>> +
>> +       return 0;
>> +}
>> +
>> +static void mtk_pll_unprepare_setclr(struct clk_hw *hw)
>> +{
>> +       struct mtk_clk_pll *pll = to_mtk_clk_pll(hw);
>> +
>> +       writel(BIT(pll->data->pll_en_bit), pll->en_clr_addr);
>> +}
>> +
>>  const struct clk_ops mtk_pll_ops = {
>>         .is_prepared    = mtk_pll_is_prepared,
>>         .prepare        = mtk_pll_prepare,
>> @@ -283,6 +309,16 @@ const struct clk_ops mtk_pll_ops = {
>>         .set_rate       = mtk_pll_set_rate,
>>  };
>>
>> +const struct clk_ops mtk_pll_fenc_clr_set_ops = {
>> +       .is_prepared    = mtk_pll_fenc_is_prepared,
>> +       .prepare        = mtk_pll_prepare_setclr,
>> +       .unprepare      = mtk_pll_unprepare_setclr,
>> +       .recalc_rate    = mtk_pll_recalc_rate,
>> +       .round_rate     = mtk_pll_round_rate,
>> +       .set_rate       = mtk_pll_set_rate,
>> +};
>> +EXPORT_SYMBOL_GPL(mtk_pll_fenc_clr_set_ops);
>> +
>>  struct clk_hw *mtk_clk_register_pll_ops(struct mtk_clk_pll *pll,
>>                                         const struct mtk_pll_data *data,
>>                                         void __iomem *base,
>> @@ -315,6 +351,9 @@ struct clk_hw *mtk_clk_register_pll_ops(struct mtk_clk_pll *pll,
>>         pll->hw.init = &init;
>>         pll->data = data;
>>
>> +       pll->fenc_addr = base + data->fenc_sta_ofs;
>> +       pll->fenc_mask = BIT(data->fenc_sta_bit);
>> +
>>         init.name = data->name;
>>         init.flags = (data->flags & PLL_AO) ? CLK_IS_CRITICAL : 0;
>>         init.ops = pll_ops;
>> @@ -337,12 +376,13 @@ struct clk_hw *mtk_clk_register_pll(const struct mtk_pll_data *data,
>>  {
>>         struct mtk_clk_pll *pll;
>>         struct clk_hw *hw;
>> +       const struct clk_ops *pll_ops = data->ops ? data->ops : &mtk_pll_ops;
>>
>>         pll = kzalloc(sizeof(*pll), GFP_KERNEL);
>>         if (!pll)
>>                 return ERR_PTR(-ENOMEM);
>>
>> -       hw = mtk_clk_register_pll_ops(pll, data, base, &mtk_pll_ops);
>> +       hw = mtk_clk_register_pll_ops(pll, data, base, pll_ops);
>>         if (IS_ERR(hw))
>>                 kfree(pll);
>>
>> diff --git a/drivers/clk/mediatek/clk-pll.h b/drivers/clk/mediatek/clk-pll.h
>> index c4d06bb11516..7fdc5267a2b5 100644
>> --- a/drivers/clk/mediatek/clk-pll.h
>> +++ b/drivers/clk/mediatek/clk-pll.h
>> @@ -29,6 +29,7 @@ struct mtk_pll_data {
>>         u32 reg;
>>         u32 pwr_reg;
>>         u32 en_mask;
>> +       u32 fenc_sta_ofs;
>>         u32 pd_reg;
>>         u32 tuner_reg;
>>         u32 tuner_en_reg;
>> @@ -51,6 +52,7 @@ struct mtk_pll_data {
>>         u32 en_clr_reg;
>>         u8 pll_en_bit; /* Assume 0, indicates BIT(0) by default */
>>         u8 pcw_chg_bit;
>> +       u8 fenc_sta_bit;
>>  };
>>
>>  /*
>> @@ -72,6 +74,8 @@ struct mtk_clk_pll {
>>         void __iomem    *en_addr;
>>         void __iomem    *en_set_addr;
>>         void __iomem    *en_clr_addr;
>> +       void __iomem    *fenc_addr;
>> +       u32             fenc_mask;
>>         const struct mtk_pll_data *data;
>>  };
>>
>> @@ -82,6 +86,7 @@ void mtk_clk_unregister_plls(const struct mtk_pll_data *plls, int num_plls,
>>                              struct clk_hw_onecell_data *clk_data);
>>
>>  extern const struct clk_ops mtk_pll_ops;
>> +extern const struct clk_ops mtk_pll_fenc_clr_set_ops;
>>
>>  static inline struct mtk_clk_pll *to_mtk_clk_pll(struct clk_hw *hw)
>>  {
>> --
>> 2.39.5
>>