EHCI: force high-speed devices to run at full speed
This patch (as710) adds a sysfs class-device attribute file named
"companion" for EHCI controllers. The file contains a list of port
numbers that are dedicated to the companion controller; by writing a
port number to the file the user can force a high-speed device
attached directly to the computer to run at full speed. (As far as I
know it is not possible to do this for a device attached to an
external hub.) A port is removed from the file by writing the
negative of its port number.
Several users have asked for this facility and it seems like a useful
thing to have. Every now and then one runs across a device which
behaves much better at full speed than at high speed.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 9ec8962..92c6291 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -388,6 +388,7 @@
/* let companion controllers work when we aren't */
ehci_writel(ehci, 0, &ehci->regs->configured_flag);
+ remove_companion_file(ehci);
remove_debug_files (ehci);
/* root hub is shut down separately (first, when possible) */
@@ -563,6 +564,7 @@
* since the class device isn't created that early.
*/
create_debug_files(ehci);
+ create_companion_file(ehci);
return 0;
}