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-rw-r--r--drivers/usb/core/hub.c23
1 files changed, 15 insertions, 8 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 90b8d43c6b3..1b1846e6473 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -432,15 +432,22 @@ static void hub_power_on(struct usb_hub *hub)
{
int port1;
unsigned pgood_delay = hub->descriptor->bPwrOn2PwrGood * 2;
- u16 wHubCharacteristics = le16_to_cpu(hub->descriptor->wHubCharacteristics);
-
- /* if hub supports power switching, enable power on each port */
- if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2) {
+ u16 wHubCharacteristics =
+ le16_to_cpu(hub->descriptor->wHubCharacteristics);
+
+ /* Enable power on each port. Some hubs have reserved values
+ * of LPSM (> 2) in their descriptors, even though they are
+ * USB 2.0 hubs. Some hubs do not implement port-power switching
+ * but only emulate it. In all cases, the ports won't work
+ * unless we send these messages to the hub.
+ */
+ if ((wHubCharacteristics & HUB_CHAR_LPSM) < 2)
dev_dbg(hub->intfdev, "enabling power on all ports\n");
- for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++)
- set_port_feature(hub->hdev, port1,
- USB_PORT_FEAT_POWER);
- }
+ else
+ dev_dbg(hub->intfdev, "trying to enable port power on "
+ "non-switchable hub\n");
+ for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++)
+ set_port_feature(hub->hdev, port1, USB_PORT_FEAT_POWER);
/* Wait at least 100 msec for power to become stable */
msleep(max(pgood_delay, (unsigned) 100));