Re: [PATCH 09/21] riscv: dma-mapping: skip invalidation before bidirectional DMA

[Lad, Prabhakar]

On Mon, Mar 27, 2023 at 1:16 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> For a DMA_BIDIRECTIONAL transfer, the caches have to be cleaned
> first to let the device see data written by the CPU, and invalidated
> after the transfer to let the CPU see data written by the device.
>
> riscv also invalidates the caches before the transfer, which does
> not appear to serve any purpose.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  arch/riscv/mm/dma-noncoherent.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Cheers,
Prabhakar

> diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> index 640f4c496d26..69c80b2155a1 100644
> --- a/arch/riscv/mm/dma-noncoherent.c
> +++ b/arch/riscv/mm/dma-noncoherent.c
> @@ -25,7 +25,7 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
>                 ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
>                 break;
>         case DMA_BIDIRECTIONAL:
> -               ALT_CMO_OP(flush, vaddr, size, riscv_cbom_block_size);
> +               ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
>                 break;
>         default:
>                 break;
> --
> 2.39.2
>
>
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