On 6/2/2020 3:05 AM, Nicolas Saenz Julienne wrote: > On Tue, 2020-05-05 at 18:13 +0200, Nicolas Saenz Julienne wrote: >> On the Raspberry Pi 4, after a PCI reset, VL805's firmware may either be >> loaded directly from an EEPROM or, if not present, by the SoC's >> VideoCore. Inform VideoCore that VL805 was just reset. >> >> Also, as this creates a dependency between USB_PCI and VideoCore's >> firmware interface, and since USB_PCI can't be set as a module neither >> this can. Reflect that on the firmware interface Kconfg. >> >> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> >> --- > > It was pointed out to me on the u-boot mailing lists that all this could be > implemented trough a reset controller. In other words have xhci get the reset > controller trough device-tree, assert it, ultamately causing the firmware > routine to be run. That is actually a clever way to solve that problem. > > As much as it pains me to go over stuff that's already 'fixed', it seems to me > it's a better solution. On one hand we get over the device-tree dependency mess > (see patch #3), and on the other we transform a pci-quirk into something less > hacky. > > That said, before getting my hands dirty, I was wondering if there is any > obvious reasons why I shouldn't do this, note that: > > - We're talking here of a PCIe XCHI device, maybe there's an issue integrating > it with DT, given the fact that, as of today, it's not really represented > there. You can always provide a PCIe device representation within the Device Tree, this is not very common, but it is sometimes useful for e.g.: assigning MAC addresses, see this example for instance: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/imx6qdl-zii-rdu2.dtsi#n647 (does not assign a MAC address, but it could). This should allow your XHCI pci_device::of_node pointer to point to node declared in the Device Tree. There you could add a 'resets' property accordingly. > > - There is no reset controller support in xhci-pci, maybe there are good > reasons why. For instance, it's not something that's reflected in any way in > the spec. It seems to me this is not usually necessary for PC systems, so it was not really needed until now. Maybe you can write a small wrapper around xhci-pci.c, similar to what xhci-plat.c does which is responsible for grabbing and releasing the reset. -- Florian
