In order for HW I/O coherency to work on Cortex-A9 based Marvell SoCs,
all MMIO registers must be mapped strongly ordered. In commit
1c8c3cf0b5 ("ARM: 8060/1: mm: allow sub-architectures to override PCI
I/O memory type") we implemented a new function,
pci_ioremap_set_mem_type(), that allow sub-architecture code to override
the memory type used to map PCI I/O regions.
In the discussion around this patch series [1], Arnd Bergmann made the
comment that maybe all PCI I/O regions should be mapped
strongly-ordered, which would have made our proposal to add
pci_ioremap_set_mem_type() irrelevant. So, we submitted a patch [2] that
did what Arnd suggested.
However, Russell in the end merged our initial proposal to add
pci_ioremap_set_mem_type(), but it was never used anywhere. Further
discussion with Arnd and other folks on IRC lead to the conclusion that
in fact using strongly-ordered for all platforms was maybe not
desirable, and therefore, using pci_ioremap_set_mem_type() was the most
appropriate solution.
As a consequence, this commit finally adds the
pci_ioremap_set_mem_type() call in the mach-mvebu platform code, which
was originally part of our initial patch series [3] and is necessary for
the whole mechanism to work.
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256565.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256755.html
[3] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256563.html
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
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