On 10/17/2011 08:35 PM, Paul Zimmerman wrote:
Hi Sebastian,
Hi Paul,
But wouldn't it be simpler and more efficient to just get rid of the
bitfields and use the normal shift and mask method to do the TRBs and
events? For e.g. high-bandwidth Isoc transfers, the driver needs to
process a _lot_ of TRBs to keep up with the USB 3.0 bandwidth. We
should avoid any unnecessary processing overhead in hot paths such as
that.
Now it is performance and not a BE problem.
The only problem with the bit fields is that each assignment is a write
access. This write access ends up in cache. So let me look at
dwc3_prepare_trbs(). You write bpl/h most likely the same way it is
now. The other two require a local variable each for setup / shifts.
Hmmm. Not sure how much overhead you save after converting.
We did this way because Felipe preferred it over bit shifts. If you want
it the other way due to performance issues then I would say please post
some numbers which prove your point.
Sebastian
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