Re: [PATCH v4 1/2] crypto: engine - support for parallel requests

[Iuliana Prodan <iuliana.prodan@nxp.com>]

On 3/12/2020 5:26 AM, Herbert Xu wrote:
> On Mon, Mar 09, 2020 at 12:51:32AM +0200, Iuliana Prodan wrote:
>>
>>   	ret = enginectx->op.do_one_request(engine, async_req);
>> -	if (ret) {
>> -		dev_err(engine->dev, "Failed to do one request from queue: %d\n", ret);
>> -		goto req_err;
>> +	can_enq_more = ret;
>> +	if (can_enq_more < 0) {
>> +		dev_err(engine->dev, "Failed to do one request from queue: %d\n",
>> +			ret);
>> +		goto req_err_1;
>> +	}
> 
> So this now includes the case of the hardware queue being full
> and the request needs to be queued until space opens up again.
> In this case, we should not do dev_err.  So you need to be able
> to distinguish between the hardware queue being full vs. a real
> fatal error on the request (e.g., out-of-memory or some hardware
> failure).
> 
There are two aspects here:
- if all requests go through crypto-engine, and, in this case, if there 
is no space in hw queue, do_one_req returns 0, and actually there will 
be no case of do_one_request() < 0;
- if there are other requests (non crypto API) that go to hw for 
execution (in CAAM we have split key or RNG) those might occupy the hw 
queue, after crypto-engine returns that it still has space. This case 
wasn't supported before my modifications and neither with these patches.
This use-case can be solved by retrying to send the request to hw - 
enqueue it back to crypto-engine, in the head of the queue (to keep the 
order, and send it again to hw).
I've tried this, but it implies modifications in all drivers. For 
example, a driver, in case of error, it frees the resources of the 
request. So, will need to map again a request.

Thanks,
Iulia