Re: [PATCH v4 5/7] riscv: mm: dma-noncoherent: Pass direction and operation to ALT_CMO_OP()

[Lad, Prabhakar]

Hi Samuel,

Thank you for the review.

On Fri, Nov 25, 2022 at 6:49 PM Samuel Holland <samuel@xxxxxxxxxxxx> wrote:
>
> On 11/24/22 13:18, Lad, Prabhakar wrote:
> > Hi Heiko,
> >
> > Thank you for the review.
> >
> > On Thu, Nov 24, 2022 at 6:29 PM Heiko Stübner <heiko@xxxxxxxxx> wrote:
> >>
> >> Am Donnerstag, 24. November 2022, 18:22:05 CET schrieb Prabhakar:
> >>> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >>>
> >>> Pass direction and operation to ALT_CMO_OP() macro.
> >>>
> >>> This is in preparation for adding errata for the Andes CPU core.
> >>
> >> can you provide more explanation why that is necessary please?
> >> I guess you want to use different cache operations for some cases?
> >>
> > Yes basically to call different cache operations based on the dir and
> > operations (and also this allows to export just one function to handle
> > the errata). I'll update the commit message in the next version.
>
> This makes things less efficient, because it requires more instructions
> and registers inside the alternative section, and your function
> duplicates the logic from arch_sync_dma_for_device(). The alternative is
> already passed the operation (clean/flush/invalidate) as a token, so you
> can construct the function name with token pasting.
>
I did think about it but that didn't help for example in the
arch_dma_prep_coherent() we are calling flush token, but on RZ/Five
for arch_dma_prep_coherent() we have to do nothing.

Cheers,
Prabhakar