linux-kernel - [PATCH v3 27/32] x86: include default ioremap

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Message-Id: <20170411122923.6285-28-lorenzo.pieralisi@arm.com>
Date:   Tue, 11 Apr 2017 13:29:07 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     linux-pci@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: [PATCH v3 27/32] x86: include default ioremap_nopost() implementation

The PCI specifications (Rev 3.0, 3.2.5 "Transaction Ordering and Posting")
mandate non-posted configuration transactions. As further highlighted in
the PCIe specifications (4.0 - Rev0.3, "Ordering Considerations for the
Enhanced Configuration Access Mechanism"), through ECAM and
ECAM-derivative configuration mechanism, the memory mapped transactions
from the host CPU into Configuration Requests on the PCI express fabric
may create ordering problems for software because writes to memory
address are typically posted transactions (unless the architecture can
enforce through virtual address mapping non-posted write transactions
behaviour) but writes to Configuration Space are not posted on the PCI
express fabric.

Include the asm-generic ioremap_nopost() implementation (currently
falling back to ioremap_nocache()) to provide a non-posted writes
ioremap interface to kernel subsystems.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Ingo Molnar <mingo@...hat.com>
---
 arch/x86/include/asm/io.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 7afb0e2..9d431ef 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -201,6 +201,7 @@ extern void set_iounmap_nonlazy(void);
 #ifdef __KERNEL__

 #include <asm-generic/iomap.h>
+#include <asm-generic/ioremap-nopost.h>

 /*
  * Convert a virtual cached pointer to an uncached pointer
-- 
2.10.0