Subject: [PATCH 2/2] ARM: OMAP2+: fix dpll round_rate() to actually round

From: [email-masked] (Tony Lindgren)
Date: Thu, 13 Feb 2014 15:00:11 -0800

* Tomi Valkeinen <[email-masked]> [140116 23:47]:
> omap2_dpll_round_rate() doesn't actually round the given rate, even if
> the name and the description so hints. Instead it only tries to find an
> exact rate match, or if that fails, return ~0 as an error.
> 
> What this basically means is that the user of the clock needs to know
> what rates the dpll can support, which obviously isn't right.
> 
> This patch adds a simple method of rounding: during the iteration, the
> code keeps track of the closest rate match. If no exact match is found,
> the closest is returned.
> 
> Signed-off-by: Tomi Valkeinen <[email-masked]>

Paul & Tero, please ack if you want me to queue this.

Tony

> ---
>  arch/arm/mach-omap2/clkt_dpll.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/clkt_dpll.c b/arch/arm/mach-omap2/clkt_dpll.c
> index 1f1708ef77bb..1b4e68dfb713 100644
> --- a/arch/arm/mach-omap2/clkt_dpll.c
> +++ b/arch/arm/mach-omap2/clkt_dpll.c
> @@ -298,6 +298,7 @@ long omap2_dpll_round_rate(struct clk_hw *hw, unsigned long target_rate,
>  	struct dpll_data *dd;
>  	unsigned long ref_rate;
>  	const char *clk_name;
> +	unsigned long diff, closest_diff = ~0;
>  
>  	if (!clk || !clk->dpll_data)
>  		return ~0;
> @@ -345,20 +346,26 @@ long omap2_dpll_round_rate(struct clk_hw *hw, unsigned long target_rate,
>  		pr_debug("clock: %s: m = %d: n = %d: new_rate = %lu\n",
>  			 clk_name, m, n, new_rate);
>  
> -		if (target_rate == new_rate) {
> +		diff = max(target_rate, new_rate) - min(target_rate, new_rate);
> +
> +		if (diff < closest_diff) {
> +			closest_diff = diff;
> +
>  			dd->last_rounded_m = m;
>  			dd->last_rounded_n = n;
> -			dd->last_rounded_rate = target_rate;
> -			break;
> +			dd->last_rounded_rate = new_rate;
> +
> +			if (diff == 0)
> +				break;
>  		}
>  	}
>  
> -	if (target_rate != new_rate) {
> +	if (closest_diff == ~0) {
>  		pr_debug("clock: %s: cannot round to rate %lu\n",
>  			 clk_name, target_rate);
>  		return ~0;
>  	}
>  
> -	return target_rate;
> +	return dd->last_rounded_rate;
>  }
>  
> -- 
> 1.8.3.2
>