On Thu, Feb 24, 2022 at 09:16:05PM +0100, Heiner Kallweit wrote: > On 24.02.2022 21:06, Jack Pham wrote: > > On Wed, Feb 23, 2022 at 05:13:03PM -0500, Alan Stern wrote: > >> On Wed, Feb 23, 2022 at 09:58:56PM +0100, Heiner Kallweit wrote: > >>> On 23.02.2022 15:17, Alan Stern wrote: > >>>> Don't change register_root_hub(). Just change xhci_plat_probe(); make > >>>> it skip the second call to usb_add_hcd() if there are no USB-3 ports. > > > > I believe this had been attempted in the past, but it does not appear > > that patch was ever accepted: > > > > https://lore.kernel.org/linux-usb/1517221474-19627-1-git-send-email-tqnguyen@xxxxxxx/ > > > I also found that xhci at several places relies on a proper shared_hcd, > even if there are no USB3 ports. Therefore maybe go with the less invasive > original version of my patch? > > https://www.spinics.net/lists/linux-usb/msg222998.html The patch that Jack refers to, written by Tung Nguyen, does always create the shared_hcd. It simply avoids registering the shared_hcd when there are no USB-3 ports. You should try that patch and see if it works on your system. Alan Stern > > Jack > > > >>> This works on my system. However a consequence is that xhci->shared_hcd > >>> is NULL. > >> > >> Why is that? xhci->shared_hcd doesn't get set in usb_add_hcd(), so > >> skipping that call shouldn't cause it to be NULL. > >> > >> Note: If you skip calling usb_add_hcd(), you will also have to skip the > >> corresponding call to usb_remove_hcd(). There may be a few more > >> subtleties involved as well; like I said before, I'm not an expert on > >> this driver. You should ask the xhci-hcd maintainer for advice. > >> > >> Alan Stern > >> > >>> There are a few places like the following in xhci.c where > >>> this may result in a NPE. Not knowing the USB subsystem in detail > >>> I can't say whether these places are in any relevant path. > >>> > >>> static int xhci_run_finished(struct xhci_hcd *xhci) > >>> { > >>> if (xhci_start(xhci)) { > >>> xhci_halt(xhci); > >>> return -ENODEV; > >>> } > >>> xhci->shared_hcd->state = HC_STATE_RUNNING; > >>> > >>> > >>> > >>>> Alan Stern > >>>> > >>>>> What I can do: submit my patches as RFC, then there's a better basis > >>>>> for a discussion. > >>>>> > >>>>>> Alan Stern > >>>>> > >>>>> Heiner > >>> > >>> Heiner >
