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.pieral...@arm.com> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: Bjorn Helgaas <bhelg...@google.com> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> Cc: Paul Mackerras <pau...@samba.org> --- arch/powerpc/include/asm/io.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h index 5ed2924..6dcd0e2 100644 --- a/arch/powerpc/include/asm/io.h +++ b/arch/powerpc/include/asm/io.h @@ -757,6 +757,7 @@ extern void __iomem *ioremap_prot(phys_addr_t address, unsigned long size, extern void __iomem *ioremap_wc(phys_addr_t address, unsigned long size); #define ioremap_nocache(addr, size) ioremap((addr), (size)) #define ioremap_uc(addr, size) ioremap((addr), (size)) +#include <asm-generic/ioremap-nopost.h> extern void iounmap(volatile void __iomem *addr); -- 2.10.0
