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

[Tero Kristo <t-kristo@ti.com>]

On 02/14/2014 01:00 AM, Tony Lindgren wrote:
> * Tomi Valkeinen <tomi.valkeinen@ti.com> [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 <tomi.valkeinen@ti.com>
>
> Paul & Tero, please ack if you want me to queue this.

The patches look good to me and based on quick testing they don't seem 
to cause any visible problems (namely this one), so acked.

-Tero

>
> 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
>>