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| author | Zhichang Yuan <yuanzhichang@hisilicon.com> | 2018-03-15 02:15:50 +0800 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2018-03-21 17:18:34 -0500 |
| commit | 031e3601869c815582ca1d49d1ff73de58e446b0 (patch) | |
| tree | 8e621f8247f2b3ba11bbb14623e3338f5260d6aa /lib/Kconfig | |
| parent | 7928b2cbe55b2a410a0f5c1f154610059c57b1b2 (diff) | |
| download | lwn-031e3601869c815582ca1d49d1ff73de58e446b0.tar.gz lwn-031e3601869c815582ca1d49d1ff73de58e446b0.zip | |
lib: Add generic PIO mapping method
41f8bba7f555 ("of/pci: Add pci_register_io_range() and
pci_pio_to_address()") added support for PCI I/O space mapped into CPU
physical memory space. With that support, the I/O ranges configured for
PCI/PCIe hosts on some architectures can be mapped to logical PIO and
converted easily between CPU address and the corresponding logical PIO.
Based on this, PCI I/O port space can be accessed via in/out accessors that
use memory read/write.
But on some platforms, there are bus hosts that access I/O port space with
host-local I/O port addresses rather than memory addresses.
Add a more generic I/O mapping method to support those devices. With this
patch, both the CPU addresses and the host-local port can be mapped into
the logical PIO space with different logical/fake PIOs. After this, all
the I/O accesses to either PCI MMIO devices or host-local I/O peripherals
can be unified into the existing I/O accessors defined in asm-generic/io.h
and be redirected to the right device-specific hooks based on the input
logical PIO.
Tested-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Zhichang Yuan <yuanzhichang@hisilicon.com>
Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
[bhelgaas: remove -EFAULT return from logic_pio_register_range() per
https://lkml.kernel.org/r/20180403143909.GA21171@ulmo, fix NULL pointer
checking per https://lkml.kernel.org/r/20180403211505.GA29612@embeddedor.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Diffstat (limited to 'lib/Kconfig')
| -rw-r--r-- | lib/Kconfig | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig index e96089499371..5fe577673b98 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -55,6 +55,22 @@ 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 |