[alsa-devel] [PATCH 1/3] ASoC: omap-mcbsp: Fix latency value calculation for pm_qos

[Peter Ujfalusi]

On 2018-11-18 19:04, Jarkko Nikula wrote:
> On 11/14/18 1:06 PM, Peter Ujfalusi wrote:
>> The latency number is in usec for the pm_qos. Correct the calculation to
>> give us the time in usec
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
>> ---
>>  sound/soc/omap/omap-mcbsp.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
>> index e0ef4774c710..a395598f1f20 100644
>> --- a/sound/soc/omap/omap-mcbsp.c
>> +++ b/sound/soc/omap/omap-mcbsp.c
>> @@ -999,9 +999,9 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
>>  			pkt_size = channels;
>>  		}
>>  
>> -		latency = ((((buffer_size - pkt_size) / channels) * 1000)
>> -				 / (params->rate_num / params->rate_den));
>> -
>> +		latency = (buffer_size - pkt_size) / channels;
>> +		latency = latency * USEC_PER_SEC /
>> +			  (params->rate_num / params->rate_den);
> 
> Did I understand correctly this doesn't fix any audio issue but allows
> CPU sleep longer or reach deeper sleep?

PM core will block any power state from where the wake-up would take
longer than the latency value.

The latency is in usec, this patch just fixing the calculation to get
the time in usec.

- Péter

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