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

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Date:   Wed, 4 Jan 2023 16:50:48 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Icenowy Zheng <uwu@...nowy.me>
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

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?

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
>


-- 
Best Regards
 Guo Ren