On 03/28/2012 05:30 PM, Richard Yang wrote:
> Experts
>
> I am reading the PCI enumeration code on x86. One thing on ACPI
> namespace puzzles me.
>
> In the initialize process, the call flow is like this
> acpi_pci_root_add()
> try_get_root_bridge_busnr()
> acpi_walk_resources(handle, METHOD_NAME__CRS,
> get_root_bridge_busnr_callback, res)
This piece of code is to invoke ACPI method "_CRS" for "handle", and call
get_root_bridge_busnr_callback for each resource descriptor returned by
this method.
Here "handle" is the object for the pci root bus or PCI host bridge.
"_CRS" is the name of ACPI method, which exists under "handle".
>
> By reading the ACPI spec, this is trying to go through the namespace and
> find the _CRS method/object.
>
> 1. Hmm... I want to know this function is trying to go through the whole
> namespace or just the device related namespace?
> 2. If it is searching the whole namespace, how could this function find the
> device specific resource just by given the "_CRS" as a parameter?
> 3. Also, if it just go through the device specific namespace, which
> parameter identify this.
>
> Here is an example in the ACPI specification in 9.11.1:
> Device (PCI0) { // PCI Root Bridge
> Name (_HID, EISAID("PNP0A03"))
> Name (_UID, 0)
> Name (_BBN, 0x00)
> Name (_SEG, 0x00) // assign segment 0 of module device to PCI0
> Name (_CRS, ResourceTemplate () {
> WordBusNumber (
> ResourceProducer,
> MinFixed, // _MIF
> MaxFixed,, // _MAF
> 0x00, // _GRA
> 0x00, // _MIN
> 0xFF, // _MAX
> 0x0, // _TRA
> 0x80) // _LEN
> WordIO (
> ResourceProducer,
> MinFixed, // _MIF
> MaxFixed,,, // _MAF
> 0x0000, // _GRA
> 0x0000, // _MIN
> 0x0CF7, // _MAX
> 0x0, // _TRA
> 0x0CF8) // _LEN
> DWordMemory (
> ResourceProducer,,
> MinNotFixed, // _MIF
> MaxNotFixed, // _MAF
> NonCacheable, // _MEM
> ReadWrite, // _RW
> 0x0FFFFFFF, // _GRA
> 0x40000000, // _MIN
> 0x5FFFFFFF, // _MAX
> 0x0, // _TRA
> 0x00000000) // _LEN
> })
> }
> }
>
> Device (PCI1) { // PCI Root Bridge
> Name (_HID, EISAID("PNP0A03"))
> Name (_UID, 0)
> Name (_BBN, 0x00)
> Name (_SEG, 0x01) // assign segment 1 of module device to PCI1
> Name (_CRS, ResourceTemplate () {
> WordBusNumber (
> ResourceProducer,
> MinFixed, //
> MaxFixed,, //
> 0x00, //
> 0x00, //
> 0x7F, //
> 0x0, //
> 0x80) //
> WordIO (
> ResourceProducer,
> MinFixed, //
> MaxFixed, //
> 0x0000, //
> 0x0D00, //
> 0x7FFF, //
> 0x0, //
> 0x7300) //
> DWordMemory (
> ResourceProducer,
> MinNotFixed,
> MaxNotFixed,
> NonCacheable,
> ReadWrite,
> 0x0FFFFFFF,
> 0x60000000,
> 0x7FFFFFFF,
> 0x0,
> 0x00000000)
> })
> }
> }
>
> We can see there are two PCI Root Bridge, and each has its own _CRS
> field. And each field has its own busnumber/iores/memios.
>
> So, in the acpi_walk_resources() function, how to find the proper _CRS
> infomation for a root device?
>
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