linux-kernel - [PATCH 02/20] PCI: fix pci_remap

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Date:   Mon, 27 Feb 2017 15:14:13 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Will Deacon <will.deacon@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Pratyush Anand <pratyush.anand@...il.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Mingkai Hu <mingkai.hu@...escale.com>,
        John Garry <john.garry@...wei.com>,
        Tanmay Inamdar <tinamdar@....com>,
        Murali Karicheri <m-karicheri2@...com>,
        Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>,
        Ray Jui <rjui@...adcom.com>,
        Wenrui Li <wenrui.li@...k-chips.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Minghuan Lian <minghuan.Lian@...escale.com>,
        Jon Mason <jonmason@...adcom.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Roy Zang <tie-fei.zang@...escale.com>
Subject: [PATCH 02/20] PCI: fix pci_remap_iospace() remap attribute

According to the PCI local bus specifications (Revision 3.0, 3.2.5),
I/O Address space transactions are non-posted. On architectures where
I/O space is implemented through a chunk of memory mapped space mapped
to PCI address space (ie IA64/ARM/ARM64) the memory mapping for the
region backing I/O Address Space transactions determines the I/O
transactions attributes (before the transactions actually reaches the
PCI bus where it is handled according to the PCI specifications).

Current pci_remap_iospace() interface, that is used to map the PCI I/O
Address Space into virtual address space, use pgprot_device() as memory
attribute for the virtual address mapping, that in some architectures
(ie ARM64) provides non-cacheable but write bufferable mappings (ie
posted writes), which clash with the non-posted write behaviour for I/O
Address Space mandated by the PCI specifications.

Update the prot ioremap_page_range() parameter in pci_remap_iospace()
to pgprot_noncached to ensure that the virtual mapping backing
I/O Address Space guarantee non-posted write transactions issued
when addressing I/O Address Space through the MMIO mapping.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Will Deacon <will.deacon@....com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Russell King <linux@...linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@....com>
---
 drivers/pci/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index bd98674..bfb3c6e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3375,7 +3375,7 @@ int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
 		return -EINVAL;

 	return ioremap_page_range(vaddr, vaddr + resource_size(res), phys_addr,
-				  pgprot_device(PAGE_KERNEL));
+				  pgprot_noncached(PAGE_KERNEL));
 #else
 	/* this architecture does not have memory mapped I/O space,
 	   so this function should never be called */
-- 
2.10.0