Re: [PATCH] arm64: Enable PCI write-combine resources under sysfs

Benjamin Herrenschmidt
2020-08-31T23:30:21Z

On Mon, 2020-08-31 at 15:18 +0000, Clint Sbisa wrote:
> Using write-combine is crucial for performance of PCI devices where
> significant amounts of transactions go over PCI BARs.
>
> arm64 supports write-combine PCI mappings, so the appropriate define
> has been added which will expose write-combine mappings under sysfs
> for prefetchable PCI resources.
>
> Signed-off-by: Clint Sbisa <csbisa@amazon.com>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> ---
> arch/arm64/include/asm/pci.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/include/asm/pci.h
> b/arch/arm64/include/asm/pci.h
> index 70b323cf8300..b33ca260e3c9 100644
> --- a/arch/arm64/include/asm/pci.h
> +++ b/arch/arm64/include/asm/pci.h
> @@ -17,6 +17,7 @@
> #define pcibios_assign_all_busses() \
> (pci_has_flag(PCI_REASSIGN_ALL_BUS))
>
> +#define arch_can_pci_mmap_wc() 1
> #define ARCH_GENERIC_PCI_MMAP_RESOURCE 1
>
> extern int isa_dma_bridge_buggy;