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[v3,06/32] avr32: include default ioremap_nopost() implementation

Message ID 20170411122923.6285-7-lorenzo.pieralisi@arm.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Lorenzo Pieralisi April 11, 2017, 12:28 p.m. UTC
The PCI specifications (Rev 3.0, 3.2.5 "Transaction Ordering and Posting")
mandate non-posted configuration transactions. As further highlighted in
the PCIe specifications (4.0 - Rev0.3, "Ordering Considerations for the
Enhanced Configuration Access Mechanism"), through ECAM and
ECAM-derivative configuration mechanism, the memory mapped transactions
from the host CPU into Configuration Requests on the PCI express fabric
may create ordering problems for software because writes to memory
address are typically posted transactions (unless the architecture can
enforce through virtual address mapping non-posted write transactions
behaviour) but writes to Configuration Space are not posted on the PCI
express fabric.

Include the asm-generic ioremap_nopost() implementation (currently
falling back to ioremap_nocache()) to provide a non-posted writes
ioremap interface to kernel subsystems.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
---
 arch/avr32/include/asm/io.h | 1 +
 1 file changed, 1 insertion(+)

Comments

Nicolas Ferre April 11, 2017, 1:55 p.m. UTC | #1
Le 11/04/2017 à 14:28, Lorenzo Pieralisi a écrit :
> The PCI specifications (Rev 3.0, 3.2.5 "Transaction Ordering and Posting")
> mandate non-posted configuration transactions. As further highlighted in
> the PCIe specifications (4.0 - Rev0.3, "Ordering Considerations for the
> Enhanced Configuration Access Mechanism"), through ECAM and
> ECAM-derivative configuration mechanism, the memory mapped transactions
> from the host CPU into Configuration Requests on the PCI express fabric
> may create ordering problems for software because writes to memory
> address are typically posted transactions (unless the architecture can
> enforce through virtual address mapping non-posted write transactions
> behaviour) but writes to Configuration Space are not posted on the PCI
> express fabric.
> 
> Include the asm-generic ioremap_nopost() implementation (currently
> falling back to ioremap_nocache()) to provide a non-posted writes
> ioremap interface to kernel subsystems.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
> Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
> ---
>  arch/avr32/include/asm/io.h | 1 +
>  1 file changed, 1 insertion(+)

You probably need to remove this one as the avr32 architecture will be
removed in kernel 4.12:

https://lkml.org/lkml/2017/3/27/422

Best regards,

> diff --git a/arch/avr32/include/asm/io.h b/arch/avr32/include/asm/io.h
> index f855646..b2ff522 100644
> --- a/arch/avr32/include/asm/io.h
> +++ b/arch/avr32/include/asm/io.h
> @@ -298,6 +298,7 @@ extern void __iounmap(void __iomem *addr);
>  #define ioremap_wc ioremap_nocache
>  #define ioremap_wt ioremap_nocache
>  #define ioremap_uc ioremap_nocache
> +#include <asm-generic/ioremap-nopost.h>
>  
>  #define cached(addr) P1SEGADDR(addr)
>  #define uncached(addr) P2SEGADDR(addr)
>
diff mbox

Patch

diff --git a/arch/avr32/include/asm/io.h b/arch/avr32/include/asm/io.h
index f855646..b2ff522 100644
--- a/arch/avr32/include/asm/io.h
+++ b/arch/avr32/include/asm/io.h
@@ -298,6 +298,7 @@  extern void __iounmap(void __iomem *addr);
 #define ioremap_wc ioremap_nocache
 #define ioremap_wt ioremap_nocache
 #define ioremap_uc ioremap_nocache
+#include <asm-generic/ioremap-nopost.h>
 
 #define cached(addr) P1SEGADDR(addr)
 #define uncached(addr) P2SEGADDR(addr)