UBUNTU: SAUCE: LIB: Introduce a generic PIO mapping method

[mirror_ubuntu-bionic-kernel.git] / lib / Kconfig

diff --git a/lib/Kconfig b/lib/Kconfig
index c5e84fbcb30b7562656dcbbc050bcc0ec4cb7a90..3b623d743db4fb4f7e64cfd661e101e2f57c2e1c 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -55,6 +55,21 @@ config ARCH_USE_CMPXCHG_LOCKREF
 config ARCH_HAS_FAST_MULTIPLIER
        bool
 
+config INDIRECT_PIO
+       bool "Access I/O in non-MMIO mode"
+       depends on ARM64
+       help
+         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.
+
 config CRC_CCITT
        tristate "CRC-CCITT functions"
        help