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. Without this waiting, VirtualBox's EHCI virtual HC accidentally hangs (see BugLink). BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211095 Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Eugene Korenevsky <ekorenevsky@xxxxxxxxxxxxx> --- v1: initial patch v2: add BugLink tag v3: add Revieved-By tags (incorrect), restore `msleep(5)` v4: remove Reviewed-By tags, restore reading from USBCMD prior to msleep, adjust description v5: add `patch changelog` v6: add `Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>` tag drivers/usb/host/ehci-hcd.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index e358ae17d51e..1926b328b6aa 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 +630,20 @@ 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); + + /* Wait until HC become operational */ ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */ msleep(5); + rc = ehci_handshake(ehci, &ehci->regs->status, STS_HALT, 0, 100 * 1000); + 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
