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

[Clint Sbisa <csbisa@amazon.com>]

On Fri, Aug 21, 2020 at 03:51:54PM +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>
> ---
>  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;
> -- 
> 2.23.3
> 

Ping. Let me know if any more info is needed.

Clint