linux-kernel - Re: [PATCH] clk: ti: divider: Add the table parsing to get the best divider value

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Date:   Wed, 25 Jan 2017 16:07:35 +0530
From:   Keerthy <j-keerthy@...com>
To:     <t-kristo@...com>
CC:     <mturquette@...libre.com>, <sboyd@...eaurora.org>,
        <linux-omap@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: ti: divider: Add the table parsing to get the best
 divider value



On Friday 02 December 2016 02:35 PM, Keerthy wrote:
> Currently the divider selection logic blindly divides the parent_rate
> by the clk rate and gives the divider value for the divider clocks
> which do not have the CLK_SET_RATE_PARENT flag set. Add the clk divider
> table parsing to get the closest divider available in the table
> provided via Device tree.
>
> The code is pretty much taken from: drivers/clk/clk-divider.c.
> and used here to fix up the best divider selection logic.

A gentle ping on this patch. This applies cleanly on the next branch as 
on today. Let me know if this needs to be rebased.

- Keerthy

>
> Signed-off-by: Keerthy <j-keerthy@...com>
> Reported-by: Richard Woodruff <r-woodruff2@...com>
> ---
>  drivers/clk/ti/divider.c | 31 ++++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/ti/divider.c b/drivers/clk/ti/divider.c
> index b4e5de1..6bb8778 100644
> --- a/drivers/clk/ti/divider.c
> +++ b/drivers/clk/ti/divider.c
> @@ -140,6 +140,35 @@ static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
>  	return true;
>  }
>
> +static int _div_round_up(const struct clk_div_table *table,
> +			 unsigned long parent_rate, unsigned long rate)
> +{
> +	const struct clk_div_table *clkt;
> +	int up = INT_MAX;
> +	int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
> +
> +	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(const struct clk_div_table *table,
> +		      unsigned long parent_rate, unsigned long rate)
> +{
> +	if (!table)
> +		return DIV_ROUND_UP(parent_rate, rate);
> +
> +	return _div_round_up(table, parent_rate, rate);
> +}
> +
>  static int ti_clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>  				  unsigned long *best_parent_rate)
>  {
> @@ -155,7 +184,7 @@ static int ti_clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
>
>  	if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
>  		parent_rate = *best_parent_rate;
> -		bestdiv = DIV_ROUND_UP(parent_rate, rate);
> +		bestdiv = _div_round(divider->table, parent_rate, rate);
>  		bestdiv = bestdiv == 0 ? 1 : bestdiv;
>  		bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
>  		return bestdiv;
>