ARM: Implement pci_remap_cfgspace() interface

The PCI bus specification (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 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@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>

3 files changed, 29 insertions, 0 deletions

diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index 42871fb8340e..2cfbc531f63b 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.
+ *
+ * The PCI specification 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 ff0eed23ddf1..fc91205ff46c 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
 
 /*
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index 3b5c7aaf9c76..2a3f6002efbc 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -433,6 +433,18 @@ void __iomem *ioremap_wc(resource_size_t res_cookie, size_t size)
 }
 EXPORT_SYMBOL(ioremap_wc);
 
+#ifdef CONFIG_PCI
+
+#include <asm/mach/map.h>
+
+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
+
 void *arch_memremap_wb(phys_addr_t phys_addr, size_t size)
 {
 	return (void *)phys_addr;