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RISC-V: Define pgprot_dmacoherent() for non-coherent devices

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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: ff689fd21c ("riscv: add RISC-V Svpbmt extension support")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Tested-by: Han Gao <rabenda.cn@gmail.com>
Tested-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Link: https://lore.kernel.org/r/20250820152316.1012757-1-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Anup Patel 2025-10-17 21:30:05 -06:00 committed by Paul Walmsley
parent fe69107ec7
commit ca525d53f9
1 changed files with 2 additions and 0 deletions
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2
arch/riscv/include/asm/pgtable.h
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@ -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