diff options
Diffstat (limited to 'drivers/usb/core/hub.c')
| -rw-r--r-- | drivers/usb/core/hub.c | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index f6c6b6f7cc9c..763c3134dd78 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -141,19 +141,27 @@ static int usb_device_supports_lpm(struct usb_device *udev) return 0; } - /* All USB 3.0 must support LPM, but we need their max exit latency - * information from the SuperSpeed Extended Capabilities BOS descriptor. + /* + * According to the USB 3.0 spec, all USB 3.0 devices must support LPM. + * However, there are some that don't, and they set the U1/U2 exit + * latencies to zero. */ if (!udev->bos->ss_cap) { - dev_warn(&udev->dev, "No LPM exit latency info found. " - "Power management will be impacted.\n"); + dev_info(&udev->dev, "No LPM exit latency info found, disabling LPM.\n"); return 0; } - if (udev->parent->lpm_capable) - return 1; - dev_warn(&udev->dev, "Parent hub missing LPM exit latency info. " - "Power management will be impacted.\n"); + if (udev->bos->ss_cap->bU1devExitLat == 0 && + udev->bos->ss_cap->bU2DevExitLat == 0) { + if (udev->parent) + dev_info(&udev->dev, "LPM exit latency is zeroed, disabling LPM.\n"); + else + dev_info(&udev->dev, "We don't know the algorithms for LPM for this host, disabling LPM.\n"); + return 0; + } + + if (!udev->parent || udev->parent->lpm_capable) + return 1; return 0; } |