Some xHCI host controllers may have optional support for Latency Tolerance Messaging (LTM). This allows USB 3.0 devices that support LTM to pass information about how much latency they can tolerate to the xHC. A PCI xHCI host will use this information to update the PCI Latency Tolerance Request (LTR) info. The goal of this is to gather latency information for the system, to enable hardware-driven C states, and the shutting down of PLLs. Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> --- drivers/usb/host/xhci-hub.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index 2732ef6..6d21030 100644 --- a/drivers/usb/host/xhci-hub.c +++ b/drivers/usb/host/xhci-hub.c @@ -508,12 +508,18 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue, if (hcd->speed != HCD_USB3) goto error; + /* Set the U1 and U2 exit latencies. */ memcpy(buf, &usb_bos_descriptor, USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE); temp = xhci_readl(xhci, &xhci->cap_regs->hcs_params3); buf[12] = HCS_U1_LATENCY(temp); put_unaligned_le16(HCS_U2_LATENCY(temp), &buf[13]); + /* Indicate whether the host has LTM support. */ + temp = xhci_readl(xhci, &xhci->cap_regs->hcc_params); + if (HCC_LTC(temp)) + buf[8] |= USB_LTM_SUPPORT; + spin_unlock_irqrestore(&xhci->lock, flags); return USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE; case GetPortStatus: -- 1.7.9 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
