Re: [PATCH 3/3] crypto: Add Allwinner Security System crypto accelerator

Marek Vasut
2014-07-23T19:46:44Z

On Wednesday, July 23, 2014 at 08:52:12 PM, Corentin LABBE wrote:
> Le 23/07/2014 17:51, Marek Vasut a écrit :
> > On Wednesday, July 23, 2014 at 04:13:09 PM, Herbert Xu wrote:
> >> On Wed, Jul 23, 2014 at 04:07:20PM +0200, Marek Vasut wrote:
> >>> On Wednesday, July 23, 2014 at 03:57:35 PM, Herbert Xu wrote:
> >>>> On Sat, May 24, 2014 at 02:00:03PM +0200, Marek Vasut wrote:
> >>>>>> + }
> >>>>>> +#endif
> >>>>>> +
> >>>>>> +#ifdef CONFIG_CRYPTO_DEV_SUNXI_SS_MD5
> >>>>>> + err = crypto_register_shash(&sunxi_md5_alg);
> >>>>>
> >>>>> Do not use shash for such device. This is clearly and ahash (and
> >>>>> async in general) device. The rule of a thumb here is that you use
> >>>>> sync algos only for devices which have dedicated instructions for
> >>>>> computing the transformation. For devices which are attached to some
> >>>>> kind of bus, you use async algos (ahash etc).
> >>>>
> >>>> I'm sorry that I didn't catch this earlier but there is no such
> >>>> rule.
> >>>>
> >>>> Unless you need the async interface you should stick to the sync
> >>>> interfaces for the sake of simplicity.
> >>>>
> >>>> We have a number of existing drivers that are synchronous but
> >>>> using the async interface. They should either be converted
> >>>> over to the sync interface or made interrupt-driven if possible.
> >>>
> >>> Sure, but this device is interrupt driven and uses DMA to feed the
> >>> crypto engine, therefore async, right ?
> >>
> >> If it's interrupt-driven, then yes it would certainly make sense to
> >> be async. But all I see is polling in the latest posting, was the
> >> first version different?
> >
> > I stand corrected then, sorry.
> >
> > Is it possible to use DMA to feed the crypto accelerator, Corentin?
> >
> > Best regards,
> > Marek Vasut
>
> Yes, DMA is possible and will be implemented soon.
> So if I have well understood, I keep using async interface.

Yeah, in this case, using DMA and async interface combo is the way to go.

Best regards,
Marek Vasut