[PATCHv2 2/4] ARM: mm: allow sub-architectures to override PCI I/O memory type

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Tue May 13 03:10:37 PDT 2014

Due to a design incompatibility between the PCIe Marvell controller
and the Cortex-A9, stressing PCIe devices with a lot of traffic
quickly causes a deadlock.

One part of the workaround for this is to have all PCIe regions mapped
as MT_MEMORY_SO instead of MT_DEVICE. While the arch_ioremap_caller()
mechanism allows sub-architecture code to override ioremap(), used to
map PCIe memory regions, there isn't such a mechanism to override the
behavior of pci_ioremap_io().

This commit adds the arch_pci_ioremap_mem_type variable, initialized
to MT_DEVICE by default, and that sub-architecture code can
override. We have chosen to expose a single variable rather than
offering the possibility of overriding the entire pci_ioremap_io(),
because implementing pci_ioremap_io() requires calling functions
(get_mem_type()) that are private to the arch/arm/mm/ code.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
 arch/arm/include/asm/io.h | 6 ++++++
 arch/arm/mm/ioremap.c     | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index 8aa4cca..3d23418 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -179,6 +179,12 @@ static inline void __iomem *__typesafe_io(unsigned long addr)
 /* PCI fixed i/o mapping */
 #define PCI_IO_VIRT_BASE	0xfee00000
+#if defined(CONFIG_PCI)
+void pci_ioremap_set_mem_type(int mem_type);
+static inline void pci_ioremap_set_mem_type(int mem_type) {}
 extern int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr);
diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index f9c32ba..d1e5ad7 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -438,6 +438,13 @@ void __arm_iounmap(volatile void __iomem *io_addr)
 #ifdef CONFIG_PCI
+static int pci_ioremap_mem_type = MT_DEVICE;
+void pci_ioremap_set_mem_type(int mem_type)
+	pci_ioremap_mem_type = mem_type;
 int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr)
 	BUG_ON(offset + SZ_64K > IO_SPACE_LIMIT);
@@ -445,7 +452,7 @@ 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,
-				  __pgprot(get_mem_type(MT_DEVICE)->prot_pte));
+				  __pgprot(get_mem_type(pci_ioremap_mem_type)->prot_pte));

More information about the linux-arm-kernel mailing list