diff options
Diffstat (limited to 'Documentation/PCI/acpi-info.rst')
| -rw-r--r-- | Documentation/PCI/acpi-info.rst | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/Documentation/PCI/acpi-info.rst b/Documentation/PCI/acpi-info.rst index 060217081c79..34c64a5a66ec 100644 --- a/Documentation/PCI/acpi-info.rst +++ b/Documentation/PCI/acpi-info.rst @@ -22,9 +22,9 @@ or if the device has INTx interrupts connected by platform interrupt controllers and a _PRT is needed to describe those connections. ACPI resource description is done via _CRS objects of devices in the ACPI -namespace [2]. The _CRS is like a generalized PCI BAR: the OS can read +namespace [2]. The _CRS is like a generalized PCI BAR: the OS can read _CRS and figure out what resource is being consumed even if it doesn't have -a driver for the device [3]. That's important because it means an old OS +a driver for the device [3]. That's important because it means an old OS can work correctly even on a system with new devices unknown to the OS. The new devices might not do anything, but the OS can at least make sure no resources conflict with them. @@ -41,15 +41,15 @@ ACPI, that device will have a specific _HID/_CID that tells the OS what driver to bind to it, and the _CRS tells the OS and the driver where the device's registers are. -PCI host bridges are PNP0A03 or PNP0A08 devices. Their _CRS should -describe all the address space they consume. This includes all the windows +PCI host bridges are PNP0A03 or PNP0A08 devices. Their _CRS should +describe all the address space they consume. This includes all the windows they forward down to the PCI bus, as well as registers of the host bridge -itself that are not forwarded to PCI. The host bridge registers include +itself that are not forwarded to PCI. The host bridge registers include things like secondary/subordinate bus registers that determine the bus range below the bridge, window registers that describe the apertures, etc. These are all device-specific, non-architected things, so the only way a PNP0A03/PNP0A08 driver can manage them is via _PRS/_CRS/_SRS, which contain -the device-specific details. The host bridge registers also include ECAM +the device-specific details. The host bridge registers also include ECAM space, since it is consumed by the host bridge. ACPI defines a Consumer/Producer bit to distinguish the bridge registers @@ -66,7 +66,7 @@ the PNP0A03/PNP0A08 device itself. The workaround was to describe the bridge registers (including ECAM space) in PNP0C02 catch-all devices [6]. With the exception of ECAM, the bridge register space is device-specific anyway, so the generic PNP0A03/PNP0A08 driver (pci_root.c) has no need to -know about it. +know about it. New architectures should be able to use "Consumer" Extended Address Space descriptors in the PNP0A03 device for bridge registers, including ECAM, @@ -75,9 +75,9 @@ ia64 kernels assume all address space descriptors, including "Consumer" Extended Address Space ones, are windows, so it would not be safe to describe bridge registers this way on those architectures. -PNP0C02 "motherboard" devices are basically a catch-all. There's no +PNP0C02 "motherboard" devices are basically a catch-all. There's no programming model for them other than "don't use these resources for -anything else." So a PNP0C02 _CRS should claim any address space that is +anything else." So a PNP0C02 _CRS should claim any address space that is (1) not claimed by _CRS under any other device object in the ACPI namespace and (2) should not be assigned by the OS to something else. |