On Thu, Jun 11, 2015 at 04:37:08PM +0300, Marcel Apfelbaum wrote: > The fixes solves the following issue: > The PXB device exposes a new pci root bridge with the > fw path: /pci-root@4/..., in which 4 is the root bus number. > Before this patch the fw path was wrongly computed: > /pci-root@1/pci@i0cf8/... > Fix the above issues: Correct the bus number and remove the > extra host bridge description.
Why is that wrong? The previous path looks correct to me. > The IEEE Std 1275-1994: > > IEEE Standard for Boot (Initialization Configuration) > Firmware: Core Requirements and Practices > 3.2.1.1 Node names > Each node in the device tree is identified by a node name > using the following notation: > driver-name@unit-address:device-arguments > > The driver name field is a sequence of between one and 31 > letters [...]. By convention, this name includes the name of > the device’s manufacturer and the device’s model name separated by > a “,”. > > The unit address field is the text representation of the > physical address of the device within the address space > defined by its parent node. The form of the text > representation is bus-dependent. Note the "physical address" part in the above. Your patch changes the "pci-root@" syntax to use a logical address instead of a physical address. That is, unless I've missed something, SeaBIOS today uses a physical address (the n'th root bus) and the patch would change it to use a logical address. One of the goals of using an "openfirmware" like address was so that they would be stable across boots (the same mechanism is also used with coreboot). Using a physical address is key for this, because simply adding or removing a PCI device could cause the logical PCI bridge enumeration to change - and that would mess up the bootorder list if it was based on logical addresses. -Kevin
