From ca525d53f994d45c8140968b571372c45f555ac1 Mon Sep 17 00:00:00 2001 From: Anup Patel Date: Fri, 17 Oct 2025 21:30:05 -0600 Subject: [PATCH] RISC-V: Define pgprot_dmacoherent() for non-coherent devices The pgprot_dmacoherent() is used when allocating memory for non-coherent devices and by default pgprot_dmacoherent() is same as pgprot_noncached() unless architecture overrides it. Currently, there is no pgprot_dmacoherent() definition for RISC-V hence non-coherent device memory is being mapped as IO thereby making CPU access to such memory slow. Define pgprot_dmacoherent() to be same as pgprot_writecombine() for RISC-V so that CPU access non-coherent device memory as NOCACHE which is better than accessing it as IO. Fixes: ff689fd21cb1 ("riscv: add RISC-V Svpbmt extension support") Signed-off-by: Anup Patel Tested-by: Han Gao Tested-by: Guo Ren (Alibaba DAMO Academy) Link: https://lore.kernel.org/r/20250820152316.1012757-1-apatel@ventanamicro.com Signed-off-by: Paul Walmsley --- arch/riscv/include/asm/pgtable.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 29e994a9afb67..5a08eb5fe99fc 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -654,6 +654,8 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot) return __pgprot(prot); } +#define pgprot_dmacoherent pgprot_writecombine + /* * Both Svade and Svadu control the hardware behavior when the PTE A/D bits need to be set. By * default the M-mode firmware enables the hardware updating scheme when only Svadu is present in -- 2.47.3