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

Arnd Bergmann
2023-03-27T12:15:57Z

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>
---
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 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