linux-kernel - [PATCH v3 2/3] riscv: dma-mapping: skip invalidation before bidirectional DMA

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Message-Id: <20230816232336.164413-3-prabhakar.mahadev-lad.rj@bp.renesas.com>
Date:   Thu, 17 Aug 2023 00:23:35 +0100
From:   Prabhakar <prabhakar.csengg@...il.com>
To:     Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Jisheng Zhang <jszhang@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Samuel Holland <samuel@...lland.org>,
        linux-riscv@...ts.infradead.org, linux-renesas-soc@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Guo Ren <guoren@...nel.org>
Subject: [PATCH v3 2/3] riscv: dma-mapping: skip invalidation before bidirectional DMA

From: Arnd Bergmann <arnd@...db.de>

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@...db.de>
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Acked-by: Palmer Dabbelt <palmer@...osinc.com>
Acked-by: Guo Ren <guoren@...nel.org>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
---
v2->v3
* No change

v1->v2
 * Included RB and ACKs
---
 arch/riscv/mm/dma-noncoherent.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index 94614cf61cdd..fc6377a64c8d 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;
-- 
2.34.1