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

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

[Clint Sbisa]

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

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

[Clint Sbisa]

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

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

[Clint Sbisa]

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
> 

Please disregard this submission, I'm resubmitting it to more appropriate
maintainers than what was suggested by the get_maintainer script.

Clint

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

[Will Deacon]

On Wed, Sep 02, 2020 at 09:22:53AM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2020-09-01 at 13:37 -0500, Bjorn Helgaas wrote:
> > On Mon, Aug 31, 2020 at 03:18:27PM +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>
> > 
> > Fine with me, I assume Will or Catalin will apply this.
> 
> Haha ! Client had sent it to them originally and I told him to resend
> it to linux-pci, yourself and Lorenzo :-)
> 
> So the confusion is on me.
> 
> Will, Catalin, it's all yours. You should have the original patch in
> your mbox already, otherwise:
> 
> https://patchwork.kernel.org/patch/11729875/

Yup, it's not the radar. We don't usually start queuing stuff until -rc3, so
I'm working through the backlog this week. Would like an Ack from Lorenzo,
though.

Will

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

[Benjamin Herrenschmidt]

On Tue, 2020-09-01 at 13:37 -0500, Bjorn Helgaas wrote:
> On Mon, Aug 31, 2020 at 03:18:27PM +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>
> 
> Fine with me, I assume Will or Catalin will apply this.

Haha ! Client had sent it to them originally and I told him to resend
it to linux-pci, yourself and Lorenzo :-)

So the confusion is on me.

Will, Catalin, it's all yours. You should have the original patch in
your mbox already, otherwise:

https://patchwork.kernel.org/patch/11729875/

Cheers,
Ben.