crypto: talitos/hash - use descriptor chaining for SEC1 instead of workqueue

crypto: talitos/hash - use descriptor chaining for SEC1 instead of workqueue

Rework the SEC1 ahash implementation to build a chain of hardware
descriptors, replacing the previous approach of submitting one
descriptor at a time via a workqueue, introduced by commit 655ef638a2bc
("crypto: talitos - fix SEC1 32k ahash request limitation").

Introduce ahash_process_req_prepare() which iterates over the request
data, allocating enough descriptors to cover the entire ahash request.
The new fields (bufsl, src, first, last) are added to talitos_edesc for
this purpose.

common_nonsnoop_hash() no longer calls talitos_submit(); it only
maps and sets up the descriptor.  Submission is now done by the caller
after the chain is built.

ahash_free_desc_list_from() takes over calling
common_nonsnoop_hash_unmap() for each descriptor during cleanup.

Compared to the workqueue based solution, request are slightly faster
since there is no more scheduling latency induced by the workqueue, and
only one interrupt is generated by the device at the end of a chain.

Commit 655ef638a2bc ("crypto: talitos - fix SEC1 32k ahash request
limitation") :

$ /usr/libexec/libkcapi/sha256sum ./test_5M.bin
013c5609d63c...  ./test_5M.bin
real 0m 0.41s
user 0m 0.01s
sys  0m 0.07s

Now :

$ /usr/libexec/libkcapi/sha256sum ./test_5M.bin
013c5609d63c...  ./test_5M.bin
real 0m 0.33s
user 0m 0.01s
sys  0m 0.20s

Tested on a system with an MPC885 SoC featuring the SEC1 Lite.

The increase in sys time is due to the fact that commit 37b5e8897eb5
("crypto: talitos - chain in buffered data for ahash on SEC1") can no
longer be applied.

Cc: stable@vger.kernel.org
Signed-off-by: Paul Louvel <paul.louvel@bootlin.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>