Re: [linux-usb-devel] [PATCH] Re-power USB ports on wakeup

[Colin Leroy <colin@colino.net>]

On 15 Mar 2005 at 17h03, David Brownell wrote:

Hi, 

> This patch is self-evidently incorrect:  by definition, a suspended
> port maintains VBUS power.  Otherwise the device connected to the
> port will get disconnected, rather than suspended ... and it won't
> be able to issue wakeup events.  All suspending does is stop sending
> USB traffic down the port, notably SOF tokens; the device connected
> to the port then enters a low power mode, typically consuming at most
> 500uA from VBUS (vs typically 100mA when it's active/configured).

Another idea. Is it harmful to "re-power" already powered ports? For
example like this:

Signed-off-by: Colin Leroy <colin@colino.net>
--- a/drivers/usb/host/ehci-hcd.c	2005-03-15 17:28:52.000000000 +0100
+++ b/drivers/usb/host/ehci-hcd.c	2005-03-16 14:44:06.000000000 +0100
@@ -773,14 +775,12 @@
 		/* here we "know" root ports should always stay powered;
 		 * but some controllers may lost all power.
 		 */
-		if (powerup) {
-			ehci_dbg (ehci, "...powerup ports...\n");
-			for (port = HCS_N_PORTS (ehci->hcs_params); port > 0; )
-				(void) ehci_hub_control(hcd,
-					SetPortFeature, USB_PORT_FEAT_POWER,
-						port--, NULL, 0);
-			msleep(20);
-		}
+		ehci_dbg (ehci, "...powerup ports...\n");
+		for (port = HCS_N_PORTS (ehci->hcs_params); port > 0; )
+			(void) ehci_hub_control(hcd,
+				SetPortFeature, USB_PORT_FEAT_POWER,
+					port--, NULL, 0);
+		msleep(20);
 	}
 
 	return retval;