The PCI bus specifications (rev 3.0, 3.2.5 "Transaction Ordering and Posting") define rules for PCI configuration space transactions ordering and posting, that state that configuration writes have to be non-posted transactions. Current ioremap interface on ARM provides mapping functions that provide "bufferable" writes transactions (ie ioremap uses MT_DEVICE memory type) aka posted writes, so PCI host controller drivers have no arch interface to remap PCI configuration space with memory attributes that comply with the PCI specifications for configuration space. Implement an ARM specific pci_remap_cfgspace() interface that allows to map PCI config memory regions with MT_UNCACHED memory type (ie strongly ordered - non-posted writes), providing a remap function that complies with PCI specifications for config space transactions. Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> --- arch/arm/include/asm/io.h | 10 ++++++++++ arch/arm/mm/ioremap.c | 7 +++++++ 2 files changed, 17 insertions(+) diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h index 42871fb..74d1b09 100644 --- a/arch/arm/include/asm/io.h +++ b/arch/arm/include/asm/io.h @@ -187,6 +187,16 @@ static inline void pci_ioremap_set_mem_type(int mem_type) {} extern int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr); /* + * PCI configuration space mapping function. + * + * PCI specifications does not allow configuration write + * transactions to be posted. Add an arch specific + * pci_remap_cfgspace definition that is implemented + * through strongly ordered memory mappings. + */ +#define pci_remap_cfgspace pci_remap_cfgspace +void __iomem *pci_remap_cfgspace(resource_size_t res_cookie, size_t size); +/* * Now, pick up the machine-defined IO definitions */ #ifdef CONFIG_NEED_MACH_IO_H diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c index ff0eed2..fc91205 100644 --- a/arch/arm/mm/ioremap.c +++ b/arch/arm/mm/ioremap.c @@ -481,6 +481,13 @@ int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr) __pgprot(get_mem_type(pci_ioremap_mem_type)->prot_pte)); } EXPORT_SYMBOL_GPL(pci_ioremap_io); + +void __iomem *pci_remap_cfgspace(resource_size_t res_cookie, size_t size) +{ + return arch_ioremap_caller(res_cookie, size, MT_UNCACHED, + __builtin_return_address(0)); +} +EXPORT_SYMBOL_GPL(pci_remap_cfgspace); #endif /* -- 2.10.0