[PATCH 07/11] ASoC: codecs: rt274: Enable irq only when needed

[Amadeusz Sławiński]

On 6/9/2022 4:18 PM, Mark Brown wrote:
> On Thu, Jun 09, 2022 at 03:35:37PM +0200, Amadeusz Sławiński wrote:
>> Interrupt is only needed when jack detection is enabled, so enable it
>> then, similarly disable it when jack detection is being disabled.
> 
>>   	if (jack == NULL) {
>>   		/* Disable jack detection */
>> +		disable_irq(rt274->i2c->irq);
> 
> There is absolutely no need to do this, it'll interfere with any sharing
> of the interrupt and if the interrupt isn't firing then there is no cost
> to having the interrupt registered.
> 
> The driver could use some cleanup of the interrupt handler, it currently
> unconditionally clears anything that fires and reports IRQ_HANDLED but
> should only report IRQ_HANDLED if there was anything from the device.
> Practically speaking it shouldn't make much difference unless there's
> spurious interrupts or the interrupt gets shared.

While this sounds fine, in tests I see that irq handler gets called 
around ~800 times per second even when we unload platform driver and 
there is no one caring about jack detection... in this case I would 
consider this to be a waste of CPU time and would prefer to just 
outright to disable it. Is there some better way to avoid unnecessary 
calls to irq handler?

Main reason why I even looked at this is pr_debug() present in 
rt298_jack_detect() which kept spamming our debug logs (~800 lines per 
second fills up logs rather fast...). It should probably be removed, as 
rt286 and rt274 do fine without having this logged, but they also call 
irq handler quite a lot if you add message log for debug.