PATCH/RFC [0/3]: Fix suspend and other acceleromter issues
werner at openmoko.org
Sun Nov 16 15:00:16 CET 2008
Simon Kagstrom wrote:
> (Email overload!)
Busy morning indeed ;-)
> This is already done in the interrupt handler for the data registers. The
> filter reset is "far" away from the data registers, so that one is read
With DMA, retrieving some unused registers should be cheap. The
amount of data is trivial anyway, and SPI+DMA can then run in
parallel to the CPU.
> The issue I see with this is that the interrupt would contine to be
> asserted until we have actually read the data values, and I don't see
> how to handle this in a good way without visiting the interrupt handler
> in a loop.
I guess looping back to the handler should be okay in this case.
This should be a rare race condition anyway. (At 10MHz, DMA should
be done reading the 20*8 = 160 bits of STATUS_REG (0x27) through
CLICK_SRC (0x39) in about 16us. A completion interrupt handler
might even consume more time than that.
> Anyway, perhaps a stupid question, but assuming we use some threshold
> configuration, is the accelerometer stuff really that much of a
> performance problem?
That's of course an excellent question :-)
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