linux-kernel - Re: [PATCH 10/21] csky: dma-mapping: skip invalidating before DMA from device

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Message-ID: <CAJF2gTT73KBZ01N2fr8z6=9XWFKo4D7cGKOtZLZeXN9NrscCXg@mail.gmail.com>
Date:   Mon, 27 Mar 2023 21:37:22 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Vineet Gupta <vgupta@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Brian Cain <bcain@...cinc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Stafford Horne <shorne@...il.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Rich Felker <dalias@...c.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        "David S. Miller" <davem@...emloft.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-oxnas@...ups.io,
        linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-openrisc@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH 10/21] csky: dma-mapping: skip invalidating before DMA
 from device

On Mon, Mar 27, 2023 at 8:15 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> csky is the only architecture that does a full flush for the
> dma_sync_*_for_device(..., DMA_FROM_DEVICE) operation. The requirement
> is only make sure there are no dirty cache lines for the buffer,
> which can be either done through an invalidate operation (as on most
> architectures including arm32, mips and arc), or a writeback (as on
> arm64 and riscv). The cache also has to be invalidated eventually but
> csky already does that after the transfer.
>
> Use a 'clean' operation here for consistency with arm64 and riscv.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/csky/mm/dma-mapping.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/csky/mm/dma-mapping.c b/arch/csky/mm/dma-mapping.c
> index 82447029feb4..c90f912e2822 100644
> --- a/arch/csky/mm/dma-mapping.c
> +++ b/arch/csky/mm/dma-mapping.c
> @@ -60,11 +60,9 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
>  {
>         switch (dir) {
>         case DMA_TO_DEVICE:
> -               cache_op(paddr, size, dma_wb_range);
> -               break;
>         case DMA_FROM_DEVICE:
>         case DMA_BIDIRECTIONAL:
> -               cache_op(paddr, size, dma_wbinv_range);
> +               cache_op(paddr, size, dma_wb_range);
Reviewed-by: Guo Ren <guoren@...nel.org>


>                 break;
>         default:
>                 BUG();
> --
> 2.39.2
>


-- 
Best Regards
 Guo Ren