Access I/O in non-MMIO mode
configname: CONFIG_INDIRECT_PIO
Linux Kernel Configuration
└─>Library routines
└─>Access I/O in non-MMIO mode
In linux kernel since version 3.10 (release Date: 2013-06-30)
On some platforms where no separate I/O space exists, there are I/O
hosts which can not be accessed in MMIO mode. Using the logical PIO
mechanism, the host-local I/O resource can be mapped into system
logic PIO space shared with MMIO hosts, such as PCI/PCIe, then the
system can access the I/O devices with the mapped-logic PIO through
I/O accessors.
This way has relatively little I/O performance cost. Please make
sure your devices really need this configure item enabled.
When in doubt, say N.
hosts which can not be accessed in MMIO mode. Using the logical PIO
mechanism, the host-local I/O resource can be mapped into system
logic PIO space shared with MMIO hosts, such as PCI/PCIe, then the
system can access the I/O devices with the mapped-logic PIO through
I/O accessors.
This way has relatively little I/O performance cost. Please make
sure your devices really need this configure item enabled.
When in doubt, say N.