On Thu, 2020-04-02 at 14:38 -0500, Bjorn Helgaas wrote: > [+cc Rob for DT platform device dependency question] > > On Thu, Apr 02, 2020 at 04:27:23PM +0200, Nicolas Saenz Julienne wrote: [...] > > Sorry it wasn't clear enough, I'll redo this comment. Also note that > > the PCIe bus and the XHCI chip are hardwired, so that's the only > > device that'll ever be available on the bus. > > > > VIA805's XHCI firmware has to be loaded trough RPi's firmware > > mailbox in between the PCIe bus probe and the subsequent USB probe. > > Note that a PCI reset clears the firmware. The only mechanism > > available in between the two operations are PCI Fixups. These are > > limited in their own way, as I can't return -EPROBE_DEFER if the > > firmware interface isn't available yet. Hence the need for an > > explicit dependency between pcie-brcmstb and raspberrypi's firmware > > mailbox device. > > > > Your concern here showcases this series' limitations. From a high > > level perspective it's not clear to me who should be responsible for > > downloading the firmware. > > I think it's fairly common for drivers to download firmware to their > devices. I guess there's not really any need to download the firmware > until a driver wants to use the device, right? > > > And I get the feeling I'm abusing PCI fixups. I haven't found any > > smart way to deal with this three way dependency of > > platform/non-platform devices. > > So IIUC, the three-way dependency involves: > > 1) brcm_pcie_probe(), which initialize the PCI host controller > platform device, enumerates PCI devices, and makes them available > for driver binding, Yes, and also resets the PCI bus, which will clear VL805's firmware (the XHCI chip). > 2) the firmware mailbox initialization (maybe > rpi_firmware_probe()?), > > 3) quirk_usb_early_handoff(), which downloads firmware to the VL805 > PCI USB adapter via rpi_firmware_init_vl805(), which uses the > firmware mailbox? And yes, that's the general idea. > Is there some way to express a dependency between > "raspberrypi,bcm2835-firmware" (the platform device claimed by > rpi_firmware_probe() and "brcm,bcm2711-pcie"? If we could ensure that > rpi_firmware_probe() runs before brcm_pcie_probe(), would that solve > part of this? That's ultimately what this patch tries to achieve. If there was a way to offload it to DT it would be way nicer. Regards, Nicolas
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