On Sat, Jan 09, 2021 at 09:18:28PM +0300, Eugene Korenevsky wrote: > According to EHCI spec, EHCI HC clears USBSTS.HCHalted whenever USBCMD.RS=1. > However, it is a good practice to wait some time after setting USBCMD.RS > (approximately 100ms) until USBSTS.HCHalted become zero. > > Instead, previous version of ehci_run() wrote 1 to USBCMD.RS, issued read to > USBCMD and waited for 5 ms. > That worked incorrectly at least for VirtualBox's EHCI virtual HC and caused > accidental hangs. > > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211095 > Reviewed-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> This is a big no-no! You must not add other people's Reviewed-by or Acked-by tags to a patch unless they give you explicit permission to do so. > Signed-off-by: Eugene Korenevsky <ekorenevsky@xxxxxxxxxxxxx> > --- > drivers/usb/host/ehci-hcd.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c > index e358ae17d51e..f3b73b5ab6e3 100644 > --- a/drivers/usb/host/ehci-hcd.c > +++ b/drivers/usb/host/ehci-hcd.c > @@ -574,6 +574,7 @@ static int ehci_run (struct usb_hcd *hcd) > struct ehci_hcd *ehci = hcd_to_ehci (hcd); > u32 temp; > u32 hcc_params; > + int rc; > > hcd->uses_new_polling = 1; > > @@ -629,9 +630,19 @@ static int ehci_run (struct usb_hcd *hcd) > down_write(&ehci_cf_port_reset_rwsem); > ehci->rh_state = EHCI_RH_RUNNING; > ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag); > - ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */ > + > + /* Wait until HC become operational */ > msleep(5); > + rc = ehci_handshake(ehci, &ehci->regs->status, STS_HALT, 0, 100 * 1000); You should not remove the ehci_readl call above. With that line gone, the PCI bus might not send the new value of configured_flag to the controller until after the 5-ms sleep has ended, which makes the msleep useless. Alan Stern > + > up_write(&ehci_cf_port_reset_rwsem); > + > + if (rc) { > + ehci_err(ehci, "USB %x.%x, controller refused to start: %d\n", > + ((ehci->sbrn & 0xf0)>>4), (ehci->sbrn & 0x0f), rc); > + return rc; > + } > + > ehci->last_periodic_enable = ktime_get_real(); > > temp = HC_VERSION(ehci, ehci_readl(ehci, &ehci->caps->hc_capbase)); > -- > 2.20.1 >
