linux-kernel - Re: [RFC PATCH 2/3] riscv: use VA+PA variant of CMO macros for DMA synchorization

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Date:   Wed, 04 Jan 2023 16:59:00 +0800
From:   Icenowy Zheng <uwu@...nowy.me>
To:     Guo Ren <guoren@...nel.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Stuebner <heiko@...ech.de>,
        Samuel Holland <samuel@...lland.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/3] riscv: use VA+PA variant of CMO macros for DMA
 synchorization

在 2023-01-04星期三的 16:50 +0800，Guo Ren写道：
> On Wed, Jan 4, 2023 at 3:43 PM Icenowy Zheng <uwu@...nowy.me> wrote:
> > 
> > DMA synchorization is done on PA and the VA is calculated from the
> > PA.
> > 
> > Use the alternative macro variant that takes both VA and PA as
> > parameters, thus in case the ISA extension used support PA
> > directly, the
> > overhead for re-converting VA to PA can be omitted.
> > 
> > Suggested-by: Guo Ren <guoren@...nel.org>
> > Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> > ---
> >  arch/riscv/mm/dma-noncoherent.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-
> > noncoherent.c
> > index d919efab6eba..a751f4aece62 100644
> > --- a/arch/riscv/mm/dma-noncoherent.c
> > +++ b/arch/riscv/mm/dma-noncoherent.c
> > @@ -19,13 +19,13 @@ void arch_sync_dma_for_device(phys_addr_t
> > paddr, size_t size,
> > 
> >         switch (dir) {
> >         case DMA_TO_DEVICE:
> > -               ALT_CMO_OP(clean, vaddr, size,
> > riscv_cbom_block_size);
> > +               ALT_CMO_OP_VPA(clean, vaddr, paddr, size,
> > riscv_cbom_block_size);
> ALT_CMO_OP -> ALT_CMO_OP_VPA, is the renaming necessary?

I didn't rename the original ALT_CMO_OP, ALT_CMO_OP_VPA is something
new.

> 
> Others:
> Reviewed-by: Guo Ren <guoren@...nel.org>
> 
> >                 break;
> >         case DMA_FROM_DEVICE:
> > -               ALT_CMO_OP(clean, vaddr, size,
> > riscv_cbom_block_size);
> > +               ALT_CMO_OP_VPA(clean, vaddr, paddr, size,
> > riscv_cbom_block_size);
> >                 break;
> >         case DMA_BIDIRECTIONAL:
> > -               ALT_CMO_OP(flush, vaddr, size,
> > riscv_cbom_block_size);
> > +               ALT_CMO_OP_VPA(flush, vaddr, paddr, size,
> > riscv_cbom_block_size);
> >                 break;
> >         default:
> >                 break;
> > @@ -42,7 +42,7 @@ void arch_sync_dma_for_cpu(phys_addr_t paddr,
> > size_t size,
> >                 break;
> >         case DMA_FROM_DEVICE:
> >         case DMA_BIDIRECTIONAL:
> > -               ALT_CMO_OP(flush, vaddr, size,
> > riscv_cbom_block_size);
> > +               ALT_CMO_OP_VPA(flush, vaddr, paddr, size,
> > riscv_cbom_block_size);
> >                 break;
> >         default:
> >                 break;
> > --
> > 2.38.1
> > 
> 
>