[alsa-devel] [PATCH 1/2] ASoC: tlv320dac33: Revisit the FIFO Mode1 handling

Peter Ujfalusi peter.ujfalusi at nokia.com
Wed Jul 28 07:08:31 CEST 2010

On Tuesday 27 July 2010 19:32:44 ext Mark Brown wrote:
> I did notice that the default changes from 20ms:
> > -#define LATENCY_TIME_MS		20
> > 
> > +	if (!dac33->mode1_i2c_latency)
> > +		dac33->mode1_i2c_latency = 10000; /* 10ms */
> to 10ms with the new code but that shouldn't be a problem.

The LATENCY_TIME_MS was used for two things:
 alarm threshold = LATENCY_TIME_MS / 2
 nSample lower limit = LATENCY_TIME_MS

The new default (10ms) comes from the old alarm threshold time.

There is no real need to limit the nSample for higher value, it is safe to use 
the same time constraint for alarm threshold and nSample lower limit.
The important thing is actually the alarm threshold value here: we need to have 
enough time to handle the interrupt, schedule the work, and write to nSample 
registers (via i2c) within certain amount of time.
Probably naming the mode1_i2c_latency differently, like mode1_latency would be 

Probably it would be better if I resend the series with this change?


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