diff mbox series

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

Message ID 20230816232336.164413-3-prabhakar.mahadev-lad.rj@bp.renesas.com (mailing list archive)
State Accepted
Commit 14be7c16d420a791f2f10276afaf7a76da17d911
Headers show
Series riscv: dma-mapping: unify support for cache flushes | expand

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conchuod/maintainers_pattern success MAINTAINERS pattern errors before the patch: 4 and now 4
conchuod/verify_signedoff success Signed-off-by tag matches author and committer
conchuod/kdoc success Errors and warnings before: 0 this patch: 0
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conchuod/build_rv64_gcc_allmodconfig success Errors and warnings before: 9 this patch: 9
conchuod/build_rv32_defconfig success Build OK
conchuod/dtb_warn_rv64 success Errors and warnings before: 12 this patch: 12
conchuod/header_inline success No static functions without inline keyword in header files
conchuod/checkpatch success total: 0 errors, 0 warnings, 0 checks, 8 lines checked
conchuod/build_rv64_nommu_k210_defconfig success Build OK
conchuod/verify_fixes success No Fixes tag
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Commit Message

Lad, Prabhakar Aug. 16, 2023, 11:23 p.m. UTC
From: Arnd Bergmann <arnd@arndb.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@arndb.de>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.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(-)

Comments

Jisheng Zhang Aug. 27, 2023, 10:22 a.m. UTC | #1
On Thu, Aug 17, 2023 at 12:23:35AM +0100, Prabhakar wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> Acked-by: Guo Ren <guoren@kernel.org>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.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);

The code could be simplified a lot since after this patch, the action
is always "clean".

Thanks
>  		break;
>  	default:
>  		break;
> -- 
> 2.34.1
>
Arnd Bergmann Aug. 27, 2023, 7:41 p.m. UTC | #2
On Sun, Aug 27, 2023, at 06:22, Jisheng Zhang wrote:
> On Thu, Aug 17, 2023 at 12:23:35AM +0100, Prabhakar wrote:
>
> The code could be simplified a lot since after this patch, the action
> is always "clean".
>

I think it's better to leave it at the elaborate version, as I still
want to merge my patch series to unify this with the other architectures,
and this would introduce a few compile-time conditionals in here.

      Arnd
diff mbox series

Patch

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;