[v5,0/3] crypto: engine - support for parallel and batch requests

Added support for executing multiple, independent or not, requests
for crypto engine based on a retry mechanism. If hardware was unable
to execute a backlog request, enqueue it back in front of crypto-engine
queue, to keep the order of requests.

Now do_one_request() returns:
>= 0: hardware executed the request successfully;
< 0: this is the old error path. If hardware has support for retry
mechanism, the backlog request is put back in front of crypto-engine
queue. For backwards compatibility, if the retry support is not available,
the crypto-engine will work as before. 
Only MAY_BACKLOG requests are enqueued back into crypto-engine's queue,
since the others can be dropped.

If hardware supports batch requests, crypto-engine can handle this use-case
through do_batch_requests callback.

Since, these new features, cannot be supported by all hardware,
the crypto-engine framework is backward compatible:
- by using the crypto_engine_alloc_init function, to initialize
crypto-engine, the new callback is NULL and retry mechanism is
disabled, so crypto-engine will work as before these changes;
- to support multiple requests, in parallel, retry_support variable
must be set on true, in driver. 
- to support batch requests, do_batch_requests callback must be
implemented in driver, to execute a batch of requests. The link
between the requests, is expected to be done in driver, in
do_one_request(). 

---
Changes since V4:
- added, in algapi a function to add a request in front of queue;
- added a retry mechanism: if hardware is unable to execute
a backlog request, enqueue it back in front of crypto-engine
queue, to keep the order of requests.

Changes since V3:
- removed can_enqueue_hardware callback and added a start-stop
mechanism based on the on the return value of do_one_request().

Changes since V2:
- readded cur_req in crypto-engine, to keep, the exact behavior as before
these changes, if can_enqueue_more is not implemented: send requests
to hardware, _one-by-one_, on crypto_pump_requests, and complete it,
on crypto_finalize_request, and so on.
- do_batch_requests is available only with can_enqueue_more.

Changes since V1:
- changed the name of can_enqueue_hardware callback to can_enqueue_more, and
the argument of this callback to crypto_engine structure (for cases when more
than ore crypto-engine is used).
- added a new patch with support for batch requests.

Changes since V0 (RFC):
- removed max_no_req and no_req, as the number of request that can be
processed in parallel;
- added a new callback, can_enqueue_more, to check whether the hardware
can process a new request.


Iuliana Prodan (3):
  crypto: algapi - create function to add request in front of queue
  crypto: engine - support for parallel requests based on retry
    mechanism
  crypto: engine - support for batch requests

 crypto/algapi.c         |  11 +++
 crypto/crypto_engine.c  | 165 ++++++++++++++++++++++++++++++++--------
 include/crypto/algapi.h |   2 +
 include/crypto/engine.h |  15 +++-
 4 files changed, 161 insertions(+), 32 deletions(-)