Re: [PATCH v2 07/22] PCI: ECAM: use ioremap_nopost() to map config region

Will Deacon
2017-03-30T16:20:03Z

On Mon, Mar 27, 2017 at 10:49:35AM +0100, Lorenzo Pieralisi wrote:
> Current ECAM kernel implementation uses ioremap() to map the ECAM
> configuration space memory region; this is not safe in that on some
> architectures the ioremap interface provides mappings that allow posted
> write transactions. This, as highlighted in the PCIe specifications
> (4.0 - Rev0.3, "Ordering Considerations for the Enhanced Configuration
> Address Mechanism"), can create ordering issues for software because
> posted writes transactions on the CPU host bus are non posted in the
> PCI express fabric.
>
> Update the ioremap() interface to use ioremap_nopost() whose
> mapping attributes guarantee that non-posted writes transactions
> are issued for memory writes within the ECAM memory mapped address
> region.
>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> ---
> drivers/pci/ecam.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)

Acked-by: Will Deacon <will.deacon@arm.com>

Will