On 06/04/2022 08:19:16-0500, Rob Herring wrote: > > > > > I've told the Xilinx folks the same thing, but I would separate this > > > > > into 2 parts. First is just h/w work in a DT based system. Second is > > > > > creating a base tree an overlay can be applied to. The first part should > > > > > be pretty straightforward. We already have PCI bus bindings. The only > > > > > tricky part is getting address translation working from leaf device thru > > > > > the PCI bus to host bus, but support for that should all be in place > > > > > (given we support ISA buses off of PCI bus). The second part will > > > > > require generating PCI DT nodes at runtime. That may be needed for both > > > > > DT and ACPI systems as we don't always describe all the PCI hierarchy > > > > > in DT. > > > > > > > > But then, if the driver generate the nodes, it will most probably > > > > have to describe the nodes by hardcoding them right ? > > > > > > No, the kernel already maintains its own tree of devices. You just > > > need to use that to generate the tree. That's really not much more > > > than nodes with a 'reg' property encoding the device and function > > > numbers. > > > > Just to clarified a point, my PCI device exposes multiple peripherals > > behind one single PCI function. > > Right. I would expect your PCI device DT node to have a 'simple-bus' > child node with all those peripherals. And maybe there's other nodes > like fixed-clocks, etc. > > > To be sure I understood what you are suggesting, you propose to create > > a DT node from the PCI driver that has been probed dynamically > > matching this same PCI device with a 'reg' property. I also think > > this would requires to generate some 'pci-ranges' to remap the > > downstream devices that are described in the DTBO, finally, load the > > overlay to be apply under this newly created node. Is that right ? > > Right. You'll need to take the BAR address(es) for the device and stick > those into 'ranges' to translate offsets to BAR+offset. > Last time I tried that, this was not working well because it means that the ranges property of the device depends on the host machine... -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
