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[PATCH v4 03/21] ARM64: implement pci_remap_cfgspace() interface

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The PCI bus specifications (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
are non-posted transactions.

This rule is reinforced by the ARM v8 architecture reference manual
(issue A.k, Early Write Acknowledgment) that explicitly recommends
that No Early Write Acknowledgment attribute should be used to map
PCI configuration (write) transactions.

Current ioremap interface on ARM64 implements mapping functions
where the Early Write Acknowledgment hint is enabled, so they
cannot be used to map PCI configuration space in a PCI specs
compliant way.

Implement an ARM64 specific pci_remap_cfgspace() interface
that allows to map PCI config region with nGnRnE attributes, providing
a remap function that complies with PCI specifications and the ARMv8
architecture reference manual recommendations.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/io.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 0c00c87..7a03250 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -173,6 +173,16 @@ extern void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size);
 #define iounmap				__iounmap
 
 /*
+ * PCI configuration space mapping function.
+ *
+ * PCI specifications disallows posted write configuration transactions.
+ * Add an arch specific pci_remap_cfgspace definition that is implemented
+ * through nGnRnE device memory attribute as recommended by the ARM v8
+ * Architecture reference manual Issue A.k B2.8.2 "Device memory".
+ */
+#define pci_remap_cfgspace(addr, size) __ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRnE))
+
+/*
  * io{read,write}{16,32,64}be() macros
  */
 #define ioread16be(p)		({ __u16 __v = be16_to_cpu((__force __be16)__raw_readw(p)); __iormb(); __v; })
-- 
2.10.0

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[PATCH v4 00/21] PCI: fix config space memory mappings Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 20/21] PCI: keystone-dw: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 17/21] PCI: tegra: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 06/21] PCI: implement Devres interface to map PCI config space Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 15/21] PCI: armada8k: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 12/21] PCI: qcom: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 19/21] PCI: layerscape: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 16/21] PCI: xgene: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 11/21] PCI: rockchip: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 07/21] PCI: ECAM: use pci_remap_cfgspace() to map config region Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 03/21] ARM64: implement pci_remap_cfgspace() interface Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
    Re: [PATCH v4 03/21] ARM64: implement pci_remap_cfgspace() interface Catalin Marinas <catalin.marinas@arm.com> - 2017-04-20 12:40 +0200
  [PATCH v4 13/21] PCI: iproc-platform: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 18/21] PCI: hisi: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  [PATCH v4 21/21] PCI: versatile: update PCI config space remap function Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> - 2017-04-19 19:00 +0200
  Re: [PATCH v4 00/21] PCI: fix config space memory mappings Bjorn Helgaas <helgaas@kernel.org> - 2017-04-20 15:30 +0200

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