| Message ID | 20170327094954.7162-6-lorenzo.pieralisi@arm.com |
|---|---|
| State | Changes Requested |
| Headers | show |
On Mon, Mar 27, 2017 at 10:49:33AM +0100, Lorenzo Pieralisi wrote: > The PCI bus specifications (rev 3.0, 3.2.5 "Transaction Ordering > and Posting") defines rules for PCI configuration space transactions > ordering and posting, that state that configuration writes > are non-posted transactions. > > This rule is reinforced by the ARM v8 architecture reference manual > (issue A.k, Early Write Acknowledgment) that explicitly recommends > that No Early Write Acknowledgment attribute should be used to map > PCI configuration (write) transactions. > > Current ioremap interface on ARM64 implements mapping functions > where the Early Write Acknowledgment hint is enabled, so they > cannot be used to map PCI configuration space in a PCI specs > compliant way. > > Implement an ARM64 specific ioremap_nopost() interface > that allows to map PCI config region with nGnRnE attributes, providing > a remap function that complies with PCI specifications and the ARMv8 > architecture reference manual recommendations. > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > --- > arch/arm64/include/asm/io.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) Acked-by: Will Deacon <will.deacon@arm.com> Let me know if you need this taken via the arm64 tree. Will
diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h index 0c00c87..1a703e5 100644 --- a/arch/arm64/include/asm/io.h +++ b/arch/arm64/include/asm/io.h @@ -173,6 +173,18 @@ extern void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size); #define iounmap __iounmap /* + * ioremap implementation providing non-posted writes (ie v8 no Early + * Write Acknowledgment) semantics. + * + * PCI specifications disallows posted write configuration transactions. + * Add an arch specific ioremap_post definition that is implemented + * through nGnRnE device memory attribute as recommended by the ARM v8 + * Architecture reference manual Issue A.k B2.8.2 "Device memory" so + * that it can be used to map PCI config space memory areas. + */ +#define ioremap_nopost(addr, size) __ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRnE)) + +/* * io{read,write}{16,32,64}be() macros */ #define ioread16be(p) ({ __u16 __v = be16_to_cpu((__force __be16)__raw_readw(p)); __iormb(); __v; })
The PCI bus specifications (rev 3.0, 3.2.5 "Transaction Ordering and Posting") defines rules for PCI configuration space transactions ordering and posting, that state that configuration writes are non-posted transactions. This rule is reinforced by the ARM v8 architecture reference manual (issue A.k, Early Write Acknowledgment) that explicitly recommends that No Early Write Acknowledgment attribute should be used to map PCI configuration (write) transactions. Current ioremap interface on ARM64 implements mapping functions where the Early Write Acknowledgment hint is enabled, so they cannot be used to map PCI configuration space in a PCI specs compliant way. Implement an ARM64 specific ioremap_nopost() interface that allows to map PCI config region with nGnRnE attributes, providing a remap function that complies with PCI specifications and the ARMv8 architecture reference manual recommendations. Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/include/asm/io.h | 12 ++++++++++++ 1 file changed, 12 insertions(+)