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Date:   Tue, 13 Oct 2020 19:36:01 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     varada@...eaurora.org
Cc:     agross@...nel.org, bjorn.andersson@...aro.org,
        catalin.marinas@....com, devicetree@...r.kernel.org,
        linus.walleij@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        mturquette@...libre.com, nsekar@...eaurora.org,
        p.zabel@...gutronix.de, robh+dt@...nel.org,
        sricharan@...eaurora.org, will@...nel.org, tdas@...eaurora.org
Subject: Re: [PATCH 1/7] clk: qcom: clk-alpha-pll: Add support for Stromer PLLs

Can you check your get_maintainers script invocation? Not sure why arm64
maintainers are Cced on a clk patch.

Quoting Varadarajan Narayanan (2020-09-27 22:15:34)
> Add programming sequence support for managing the Stromer
> PLLs.
> 
> Signed-off-by: Varadarajan Narayanan <varada@...eaurora.org>
> ---
>  drivers/clk/qcom/clk-alpha-pll.c | 156 ++++++++++++++++++++++++++++++++++++++-
>  drivers/clk/qcom/clk-alpha-pll.h |   5 ++
>  2 files changed, 160 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
> index 26139ef..ce3257f 100644
> --- a/drivers/clk/qcom/clk-alpha-pll.c
> +++ b/drivers/clk/qcom/clk-alpha-pll.c
> @@ -116,6 +116,19 @@ const u8 clk_alpha_pll_regs[][PLL_OFF_MAX_REGS] = {
>                 [PLL_OFF_OPMODE] = 0x38,
>                 [PLL_OFF_ALPHA_VAL] = 0x40,
>         },
> +

Nitpick: Drop this newline.

> +       [CLK_ALPHA_PLL_TYPE_STROMER] = {
> +               [PLL_OFF_L_VAL] = 0x08,
> +               [PLL_OFF_ALPHA_VAL] = 0x10,
> +               [PLL_OFF_ALPHA_VAL_U] = 0x14,
> +               [PLL_OFF_USER_CTL] = 0x18,
> +               [PLL_OFF_USER_CTL_U] = 0x1c,
> +               [PLL_OFF_CONFIG_CTL] = 0x20,
> +               [PLL_OFF_CONFIG_CTL_U] = 0xff,
> +               [PLL_OFF_TEST_CTL] = 0x30,
> +               [PLL_OFF_TEST_CTL_U] = 0x34,
> +               [PLL_OFF_STATUS] = 0x28,
> +       },
>  };
>  EXPORT_SYMBOL_GPL(clk_alpha_pll_regs);
>  
> @@ -127,6 +140,8 @@ EXPORT_SYMBOL_GPL(clk_alpha_pll_regs);
>  #define ALPHA_BITWIDTH         32U
>  #define ALPHA_SHIFT(w)         min(w, ALPHA_BITWIDTH)
>  
> +#define        PLL_STATUS_REG_SHIFT    8

This should have an ALPHA_ prefix.

> +
>  #define PLL_HUAYRA_M_WIDTH             8
>  #define PLL_HUAYRA_M_SHIFT             8
>  #define PLL_HUAYRA_M_MASK              0xff
> @@ -240,14 +255,143 @@ void clk_alpha_pll_configure(struct clk_alpha_pll *pll, struct regmap *regmap,
>         mask |= config->pre_div_mask;
>         mask |= config->post_div_mask;
>         mask |= config->vco_mask;
> +       mask |= config->alpha_en_mask;
> +       mask |= config->alpha_mode_mask;
>  
>         regmap_update_bits(regmap, PLL_USER_CTL(pll), mask, val);
>  
> +       /* Stromer APSS PLL does not enable LOCK_DET by default, so enable it */
> +       val_u = config->status_reg_val << PLL_STATUS_REG_SHIFT;
> +       val_u |= config->lock_det;
> +
> +       mask_u = config->status_reg_mask;
> +       mask_u |= config->lock_det;
> +
> +       if (val_u != 0)

if (val_u) is more canonical.

> +               regmap_update_bits(regmap, PLL_USER_CTL_U(pll), mask_u, val_u);
> +
> +       if (config->test_ctl_val != 0)

Same comment

> +               regmap_write(regmap, PLL_TEST_CTL(pll), config->test_ctl_val);
> +
> +       if (config->test_ctl_hi_val != 0)

Same comment

> +               regmap_write(regmap, PLL_TEST_CTL_U(pll), config->test_ctl_hi_val);
> +
>         if (pll->flags & SUPPORTS_FSM_MODE)
>                 qcom_pll_set_fsm_mode(regmap, PLL_MODE(pll), 6, 0);
>  }
>  EXPORT_SYMBOL_GPL(clk_alpha_pll_configure);
>  
> +static unsigned long
> +alpha_pll_stromer_calc_rate(u64 prate, u32 l, u64 a)
> +{
> +       return (prate * l) + ((prate * a) >> ALPHA_REG_BITWIDTH);

Is this not already in this file? Why can't we use
alpha_pll_calc_rate()?

> +}
> +
> +static unsigned long
> +alpha_pll_stromer_round_rate(unsigned long rate, unsigned long prate, u32 *l, u64 *a)
> +{
> +       u64 remainder;
> +       u64 quotient;
> +
> +       quotient = rate;
> +       remainder = do_div(quotient, prate);
> +       *l = quotient;
> +
> +       if (!remainder) {
> +               *a = 0;
> +               return rate;
> +       }
> +
> +       quotient = remainder << ALPHA_REG_BITWIDTH;
> +
> +       remainder = do_div(quotient, prate);
> +
> +       if (remainder)
> +               quotient++;
> +
> +       *a = quotient;
> +       return alpha_pll_stromer_calc_rate(prate, *l, *a);
> +}
> +
> +static unsigned long
> +clk_alpha_pll_stromer_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
> +{
> +       u32 l, low, high, ctl;
> +       u64 a = 0, prate = parent_rate;
> +       struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> +
> +       regmap_read(pll->clkr.regmap, PLL_L_VAL(pll), &l);
> +
> +       regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &ctl);
> +       if (ctl & PLL_ALPHA_EN) {
> +               regmap_read(pll->clkr.regmap, PLL_ALPHA_VAL(pll), &low);
> +               regmap_read(pll->clkr.regmap, PLL_ALPHA_VAL_U(pll),
> +                           &high);
> +               a = (u64)high << ALPHA_BITWIDTH | low;
> +       }
> +
> +       return alpha_pll_stromer_calc_rate(prate, l, a);
> +}
> +
> +static int clk_alpha_pll_stromer_determine_rate(struct clk_hw *hw,
> +                                        struct clk_rate_request *req)
> +{
> +       unsigned long rate = req->rate;
> +       u32 l;
> +       u64 a;
> +
> +       rate = alpha_pll_stromer_round_rate(rate, req->best_parent_rate, &l, &a);

Why assign to rate if nobody is going to look at it? Should probably be
set to req->rate instead?

> +
> +       return 0;
> +}
> +
> +static int clk_alpha_pll_stromer_set_rate(struct clk_hw *hw, unsigned long rate,
> +                                        unsigned long prate)
> +{
> +       struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
> +       u32 l;
> +       int ret;
> +       u64 a;
> +
> +       rate = alpha_pll_stromer_round_rate(rate, prate, &l, &a);
> +
> +       /* Write desired values to registers */

Please drop this useless comment.

> +       regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
> +       regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
> +       regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL_U(pll),
> +                                       a >> ALPHA_BITWIDTH);
> +
> +       regmap_update_bits(pll->clkr.regmap, PLL_USER_CTL(pll),
> +                          PLL_ALPHA_EN, PLL_ALPHA_EN);
> +
> +       if (!clk_hw_is_enabled(hw))
> +               return 0;
> +
> +       /* Stromer PLL supports Dynamic programming.

The /* goes on a line by itself.

> +        * It allows the PLL frequency to be changed on-the-fly without first
> +        * execution of a shutdown procedure followed by a bring up procedure.
> +        */

Cool feature. Maybe that can go into the header file though?

> +
> +       regmap_update_bits(pll->clkr.regmap, PLL_MODE(pll), PLL_UPDATE,
> +                          PLL_UPDATE);
> +       /* Make sure PLL_UPDATE request goes through */
> +       mb();

regmap APIs already have memory barriers so this isn't needed?

> +
> +       /* Wait for PLL_UPDATE to be cleared */

I think the code already says this so we can just drop this comment.

> +       ret = wait_for_pll_update(pll);
> +       if (ret)
> +               return ret;
> +
> +       /* Wait 11or more PLL clk_ref ticks[to be explored more on wait] */
> +

Is this a TODO?

> +       /* Poll LOCK_DET for one */

I think the code already says this so we can just drop this comment.

> +       ret = wait_for_pll_enable_lock(pll);
> +       if (ret)
> +               return ret;
> +
> +       return 0;
> +}
> +
>  static int clk_alpha_pll_hwfsm_enable(struct clk_hw *hw)
>  {
>         int ret;

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