linux-kernel - Re: [PATCH v3 2/5] clk: rockchip: fix up the frac clk get rate error

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Message-Id: <20191003181102.803B120862@mail.kernel.org>
Date:   Thu, 03 Oct 2019 11:11:01 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Elaine Zhang <zhangqing@...k-chips.com>, heiko@...ech.de
Cc:     mturquette@...libre.com, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        xxx@...k-chips.com, xf@...k-chips.com, huangtao@...k-chips.com,
        Elaine Zhang <zhangqing@...k-chips.com>
Subject: Re: [PATCH v3 2/5] clk: rockchip: fix up the frac clk get rate error

Quoting Elaine Zhang (2019-09-26 20:00:41)
> support fractional divider with only one level parent clock

Please put a lot more description in here. A single sentence doesn't
help anyone understand the motivation for the change.

> 
> Signed-off-by: Elaine Zhang <zhangqing@...k-chips.com>
> ---
>  drivers/clk/rockchip/clk.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c
> index fac5a4a3f5c3..8f77c3f9fab7 100644
> --- a/drivers/clk/rockchip/clk.c
> +++ b/drivers/clk/rockchip/clk.c
> @@ -190,16 +190,21 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
>         if (((rate * 20 > p_rate) && (p_rate % rate != 0)) ||
>             (fd->max_prate && fd->max_prate < p_rate)) {
>                 p_parent = clk_hw_get_parent(clk_hw_get_parent(hw));
> -               p_parent_rate = clk_hw_get_rate(p_parent);
> -               *parent_rate = p_parent_rate;
> -               if (fd->max_prate && p_parent_rate > fd->max_prate) {
> -                       div = DIV_ROUND_UP(p_parent_rate, fd->max_prate);
> -                       *parent_rate = p_parent_rate / div;
> +               if (!p_parent) {
> +                       *parent_rate = p_rate;
> +               } else {
> +                       p_parent_rate = clk_hw_get_rate(p_parent);
> +                       *parent_rate = p_parent_rate;
> +                       if (fd->max_prate && p_parent_rate > fd->max_prate) {
> +                               div = DIV_ROUND_UP(p_parent_rate,
> +                                                  fd->max_prate);
> +                               *parent_rate = p_parent_rate / div;
> +                       }
>                 }
>  
>                 if (*parent_rate < rate * 20) {
> -                       pr_err("%s parent_rate(%ld) is low than rate(%ld)*20, fractional div is not allowed\n",
> -                              clk_hw_get_name(hw), *parent_rate, rate);
> +                       pr_warn("%s p_rate(%ld) is low than rate(%ld)*20, use integer or half-div\n",
> +                               clk_hw_get_name(hw), *parent_rate, rate);

Hm.. now it's changed to a warning?

>                         *m = 0;
>                         *n = 1;
>                         return;
> -- 
> 1.9.1
> 
> 
>