Re: [PATCH 3/4] clk: mediatek: Add configurable enable control to mtk_pll_data

From: Nicolas Boichat
Date: Wed Jul 22 2020 - 04:52:14 EST


On Wed, Jul 22, 2020 at 2:50 PM Weiyi Lu <weiyi.lu@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
> 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.

> + 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