PATCH/RFC [0/3]: Fix suspend and other acceleromter issues

Andy Green andy at
Sun Nov 16 20:17:14 CET 2008

Hash: SHA1

Somebody in the thread at some point said:
| Andy Green wrote:
|> As Simon suggests the DMA thing doesn't buy us much in practice,
| The reason I keep on bringing up DMA is that this is the only way to
| get anything even remotely efficient from that SPI hardware. There's
| no FIFO, so you have to handle each byte individually (unless you
| have DMA).
| From my experiments with SPI for WLAN, I know that interrupt-driven
| SPI is extremely ineffient:

Not so, the bitbang implementation I did reads and writes an arbitrary
number of bytes in one hit each WITHOUT interrupts.  The "without
interrupts" bit is the point.;a=blob;f=arch/arm/mach-s3c2440/mach-gta02.c;h=ac2e5b615ef234c0d34d63a3e7f55468220f279b;hb=stable-tracking#l1048

More importantly there is a general feature here to be able to use
bitbang SPI at all on any platform inside interrupt context... you can't
do it right now using current Linux APIs.  A general solution there for
our existing bitbang method both reintegrates us into Linux mainstream
SPI bitbang API world and increases chance to sell the solution upstream
along with our lis302dl driver using it.

- -Andy

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