[linux-dvb] Flooding interrupts

Hartmut Hackmann hartmut.hackmann at t-online.de
Wed Sep 27 00:02:30 CEST 2006


Hi,

Manu Abraham wrote:
> Hartmut Hackmann wrote:
> 
>>Hi,
>>
>>Jimmy Hedman wrote:
>>
>>>Hi,
>>>I have a Compro DVB-T 300 which uses the saa7134-dvb-driver. When it's
>>>tuned it is flooding my system with between 12000 and 16000 interrupts a
>>>second. It works, but that amout of interrupts doesn't sound healty. Any
>>>ideas what this could be?
>>>
>>>Many thanks in advance,
>>>Jimmy Hedman
>>>
>>
>>The streaming DMA causes loads of interrupts, but not that many.
> 
> 
> Whether it be consistent or streaming, this has nothing to do with the
> interrupt count. The only case when you have too many interrupts is when
> your buffers are too small, causing the device requesting the host to
> read from the DMA buffers.
> 
> 
>>For DVB-T you should expect about 70 per sec, and for analog, its
>>up to 50 per sec for 50Hz systems.
>>The only other valid interrupt source are the GPIOs (Remote control).
>>If there really are so many interrupts, there must be something wrong
>>with the GPIO config but i don't think so.
> 
The buffer size for DVB is fixed, at 14MBit it gives the number of
buffer full IRQs i mentioned above (70 per sec). For analog, its easier.
The buffers always hold fields / frames. I forgot the sound DMA buffers,
which give about 32 IRQs per sec.
So the streaming causes about 150 IRQs per second if everything is
running.

Hartmut



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