RE: [PATCH v2 4/4] crypto: starfive - Add hash and HMAC support

[JiaJie Ho]

> -----Original Message-----
> From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Sent: 14 February, 2023 2:13 PM
> To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: JiaJie Ho <jiajie.ho@xxxxxxxxxxxxxxxx>; David S . Miller
> <davem@xxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Krzysztof
> Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Emil Renner Berthing
> <kernel@xxxxxxxx>; Conor Dooley <conor.dooley@xxxxxxxxxxxxx>; linux-
> crypto@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-riscv@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 4/4] crypto: starfive - Add hash and HMAC support
> 
> On Thu, Feb 09, 2023 at 05:43:34PM +0800, Herbert Xu wrote:
> > On Thu, Feb 09, 2023 at 09:33:06AM +0000, JiaJie Ho wrote:
> > >
> > > The DMA can only support 32-bit addressing.
> > > So, I am copying everything in case kernel allocated memory region >32-
> bit for a user app.
> >
> > Does your hardware support scatter-and-gather? If so you should at
> > least allocate individual pages rather than one contiguous buffer.
> >
> > Then you can allocate them on-demand rather than before-hand.
> >
> > It would also be nice to not do the copy if the input you were given
> > was in low memory (and contiguous if your hardware doesn't do SG).
> 
> All of that is done by the DMA API, or more specifically swiotlb and does not
> need to be duplicated in individual drivers.

I'll update the driver accordingly.
Thanks Christoph and Herbert for the pointers.

Regards
Jia Jie