Arnd Bergmann explains: "The PCI I/O space semantics require non-posted writes, which is the main difference between device and strongly-ordered mappings."
This patch therefore changes the memory type used for PCI I/O mappings from MT_DEVICE to MT_UNCACHED. On Marvell EBU platforms, it is part of a workaround for a deadlock situation occuring on Armada 375/38x between PCIe/PL310 and hardware I/O coherency in SMP situations. As Arnd Bergmann indicates: "the same fix is required both for mvebu as a workaround for the deadlock as well as for everyone else as a fix for an incorrect PCI behavior." Signed-off-by: Thomas Petazzoni <[email protected]> --- arch/arm/mm/ioremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c index f9c32ba..631b0e6 100644 --- a/arch/arm/mm/ioremap.c +++ b/arch/arm/mm/ioremap.c @@ -445,7 +445,7 @@ int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr) return ioremap_page_range(PCI_IO_VIRT_BASE + offset, PCI_IO_VIRT_BASE + offset + SZ_64K, phys_addr, - __pgprot(get_mem_type(MT_DEVICE)->prot_pte)); + __pgprot(get_mem_type(MT_UNCACHED)->prot_pte)); } EXPORT_SYMBOL_GPL(pci_ioremap_io); #endif -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
