linux-kernel - Re: [PATCH RESEND 2/2] drivers: clk: zynqmp: update divider round rate logic

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Date:   Mon, 23 Oct 2023 20:37:49 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jay Buddhabhatti <jay.buddhabhatti@....com>, michal.simek@....com,
        mturquette@...libre.com
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Jay Buddhabhatti <jay.buddhabhatti@....com>
Subject: Re: [PATCH RESEND 2/2] drivers: clk: zynqmp: update divider round rate logic

Quoting Jay Buddhabhatti (2023-10-16 04:30:02)
> Currently zynqmp divider round rate is considering single parent and
> calculating rate and parent rate accordingly. But if divider clock flag
> is set to SET_RATE_PARENT then its not trying to traverse through all
> parent rate and not selecting best parent rate from that. So use common
> divider_round_rate() which is traversing through all clock parents and
> its rate and calculating proper parent rate.
> 
> Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@....com>
> ---
>  drivers/clk/zynqmp/divider.c | 70 ++++++------------------------------
>  1 file changed, 10 insertions(+), 60 deletions(-)

Can't argue against removing that many lines!

> 
> diff --git a/drivers/clk/zynqmp/divider.c b/drivers/clk/zynqmp/divider.c
> index 33a3b2a22659..a42c183d7e5d 100644
> --- a/drivers/clk/zynqmp/divider.c
> +++ b/drivers/clk/zynqmp/divider.c
> @@ -193,23 +149,17 @@ static long zynqmp_clk_divider_round_rate(struct clk_hw *hw,
>                 return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
>         }
>  
> -       bestdiv = zynqmp_divider_get_val(*prate, rate, divider->flags);
> -
> -       /*
> -        * In case of two divisors, compute best divider values and return
> -        * divider2 value based on compute value. div1 will  be automatically
> -        * set to optimum based on required total divider value.
> -        */
> -       if (div_type == TYPE_DIV2 &&
> -           (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
> -               zynqmp_get_divider2_val(hw, rate, divider, &bestdiv);
> +       max = divider->max_div;
> +       while (max != 0) {
> +               if ((max & 1) == 1)
> +                       width++;
> +               max = max >> 1;

Is this ffs()?

>         }
>  
> -       if ((clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) && divider->is_frac)
> -               bestdiv = rate % *prate ? 1 : bestdiv;
> +       rate = divider_round_rate(hw, rate, prate, NULL, width, divider->flags);
>  
> -       bestdiv = min_t(u32, bestdiv, divider->max_div);
> -       *prate = rate * bestdiv;
> +       if (divider->is_frac && (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) && (rate % *prate))
> +               *prate = rate;