linux-kernel - Re: [PATCH 1/3] clk: divider: Fix best div calculation for power-of-two and table dividers

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Date:	Fri, 25 Apr 2014 08:31:26 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	Maxime COQUELIN <maxime.coquelin@...com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	kernel@...inux.com, maxime.coquelin@...com
Subject: Re: [PATCH 1/3] clk: divider: Fix best div calculation for power-of-two and
 table dividers

Quoting Maxime COQUELIN (2014-01-29 08:24:06)
> The divider returned by clk_divider_bestdiv() is likely to be invalid in case
> of power-of-two and table dividers when CLK_SET_RATE_PARENT flag isn't set.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@...com>

I've taken this into clk-fixes for 3.15-rcX.

Thanks,
Mike

> ---
>  drivers/clk/clk-divider.c |   37 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index 5543b7d..2137d58 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -144,6 +144,37 @@ static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
>         return true;
>  }
>  
> +static int _round_up_table(const struct clk_div_table *table, int div)
> +{
> +       const struct clk_div_table *clkt;
> +       int up = _get_table_maxdiv(table);
> +
> +       for (clkt = table; clkt->div; clkt++) {
> +               if (clkt->div == div)
> +                       return clkt->div;
> +               else if (clkt->div < div)
> +                       continue;
> +
> +               if ((clkt->div - div) < (up - div))
> +                       up = clkt->div;
> +       }
> +
> +       return up;
> +}
> +
> +static int _div_round_up(struct clk_divider *divider,
> +               unsigned long parent_rate, unsigned long rate)
> +{
> +       int div = DIV_ROUND_UP(parent_rate, rate);
> +
> +       if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
> +               div = __roundup_pow_of_two(div);
> +       if (divider->table)
> +               div = _round_up_table(divider->table, div);
> +
> +       return div;
> +}
> +
>  static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>                 unsigned long *best_parent_rate)
>  {
> @@ -159,7 +190,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>  
>         if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
>                 parent_rate = *best_parent_rate;
> -               bestdiv = DIV_ROUND_UP(parent_rate, rate);
> +               bestdiv = _div_round_up(divider, parent_rate, rate);
>                 bestdiv = bestdiv == 0 ? 1 : bestdiv;
>                 bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
>                 return bestdiv;
> @@ -219,6 +250,10 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
>         u32 val;
>  
>         div = parent_rate / rate;
> +
> +       if (!_is_valid_div(divider, div))
> +               return -EINVAL;
> +
>         value = _get_val(divider, div);
>  
>         if (value > div_mask(divider))
> -- 
> 1.7.9.5
> 
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