Sahara performance on i.MX53

[Martin Fuzzey]

Hi,

I've been trying the Sahara crypto module on i.MX53 [mainline 3.19 
kernel + b251638c46a (crypto: sahara - use the backlog)]

I tested using dm-crypt with AES-128:
cryptsetup -v  --key-size=128 luksFormat /dev/mmcblk0p7
cryptsetup luksOpen /dev/mmcblk0p7 cryptotest

dd if=/dev/mapper/cryptotest of=/dev/null bs=1M count=100


CPU Freq (MHz)       Time (s) WITHOUT Sahara        Time (s) WITH Sahara
1200                          3.26         5.34
1000                          3.26         5.62
800                            4.0           6.24
400                            7.72         9.86
166                            18.42       18.87

I was hoping for something better.
There is a reduction in CPU usage as expected but the performance 
figures aren't looking very good.
As this is in kernel use by dm-crypt cryptodev or af_alg aren't involved.

Has anyone else done any measurements?

Something wrong with my setup or with my expectations?

Regards,

Martin