On 04/26/2016 10:39 PM, Bjorn Helgaas wrote:
On Fri, Apr 15, 2016 at 07:06:40PM +0200, Tomasz Nowicki wrote:
Platforms that have memory mapped IO port (such as ARM64) need special handling for PCI I/O resources. For host bridge's resource probing case these resources need to be fixed up with pci_register_io_range/pci_remap_iospace etc.
ia64 also has memory-mapped I/O port space.
The specific references of interest to anyone here are:
*). Volume 2, Part 1: Itanium® Architecture-based Operating System Interaction Model with IA-32 Applications 2:267 section "10.7 I/O Port Space Model" which describes how they can map 4 "legacy" IO ports on a virtual page when operating in a "sparse" mode.
*). Page 378 of the ACPI6.1 specification Table 6-213 I/O Resource Flag (Resource Type = 1) Definitions describes how a "sparse" translation can exist depending upon bit _TRS. This seems to be implemented in Linux using the ACPI_SPARSE_TRANSLATION types.
It would be ideal to find some way to handle ia64 and ARM64 similarly. At the very least, we have to make sure that this doesn't break ia64. The ia64 dense/sparse I/O spaces complicate things; I don't know if ARM64 has something similar or not.
There's nothing directly similar - it's just regular MMIO.
Jon.