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[v3,1/3] riscv: dma-mapping: only invalidate after DMA, not flush

Message ID 20230816232336.164413-2-prabhakar.mahadev-lad.rj@bp.renesas.com (mailing list archive)
State Accepted
Delegated to: Geert Uytterhoeven
Headers show
Series riscv: dma-mapping: unify support for cache flushes | expand

Commit Message

Prabhakar Aug. 16, 2023, 11:23 p.m. UTC 
From: Arnd Bergmann <arnd@arndb.de>

No other architecture intentionally writes back dirty cache lines into
a buffer that a device has just finished writing into. If the cache is
clean, this has no effect at all, but if a cacheline in the buffer has
actually been written by the CPU,  there is a driver bug that is likely
made worse by overwriting that buffer.

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>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
v2->v3
* No change

v1->v2
* Fixed typo drive->driver in commit message
* Included RB and ACKs
---
 arch/riscv/mm/dma-noncoherent.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index d51a75864e53..94614cf61cdd 100644
--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -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(inval, vaddr, size, riscv_cbom_block_size);
 		break;
 	default:
 		break;