[PATCH 0/4] dmaengine: omap-dma: transfer start and short memcpy improvement

From: Peter Ujfalusi
Date: Wed Nov 11 2015 - 05:39:30 EST


The first two patch is trivial fix.
The third (remove the tasklet use for starting the transfer):
I had been wondering about this for a while and now I was able to spend some
time to look at this in more detail.
In 'normal' operation I have never seen the tasklet to start more then one
transfer even when pushing I/O based workloads on the board. However when I run
the DMAtest module I can see that the tasklet executes about 15 transfers.
When the tasklet use has been removed, everything worked as well as before but
the throughput of MMC/SD and memcpy increased slightly:

dd if=/dev/mmcblk0 of=/dev/null bs=64k count=24000
~16.5 MB/s -> ~16.6 MB/s

echo 6553 > /sys/module/dmatest/parameters/test_buf_size
echo 2000 > /sys/module/dmatest/parameters/timeout
echo 5000 > /sys/module/dmatest/parameters/iterations
~585 KB/s -> ~638 KB/s

It worth mentioning that _with_ the tasklet starting the transfers I managed to
hit a situation once when for some reason the memcpy tests were started to time
out. This happend with memcpy, iozone, dd and grep -R blabla /usr/ running at
the same time.

The last patch is to correct the behaviour of omap-dma when short memcpy is used
by a client and the client is not using completion, but polling for the end of
the transfer.

Peter Ujfalusi (4):
dmaengine: omap-dma: Correct status reporting for memcpy
dmaengine: omap-dma: Clean up the prep_slave_sg sg list walk code
dmaengine: omap-dma: Remove tasklet to start the transfers
dmaengine: omap-dma: Handle cases when the channel is polled for

drivers/dma/omap-dma.c | 78 +++++++++-----------------------------------------
1 file changed, 14 insertions(+), 64 deletions(-)


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