diff options
authorJohn Stultz <john.stultz@linaro.org>2011-07-20 17:09:34 -0700
committerJohn Stultz <john.stultz@linaro.org>2011-07-25 10:43:19 -0700
commitf5968c8833f0985b76d38593892acd6558bab149 (patch)
parent21a602b5cdc203cbcf8bbeeb26edeb3de7c65955 (diff)
musb: Avoid musb_gadget_pullup "Unhandled fault" oops on omap4linux-linaro-3.0-2011.07-1-android-1
I've recently run across an "Unhandled fault: imprecise external abort" oops that is caused when a driver called usb_gadget_connect() when there was no cable plugged into the musb gadget port. You can see the oops message here: https://launchpadlibrarian.net/75635123/minicom.txt Doing some digging, it seemed the problem was triggered when reading from the musb registers in musb_pullup() when the device controller is powered down. Looking at other examples of where the registers were accessed, I noticed they were always enclosed by pm_runtime_get/put calls. So I added such calls to the musb_gadget_pullup() function and it seemed to resolve the problem. Now, full disclosure: this was triggered with the out-of-tree Android adb gadget driver. However, I suspect the same behavior could be triggered using the composite gadget driver as well, so I think this is a generic issue. However, if I'm wrong, let me know and I'll try to make sure the fix is done in the right place. If this is the right fix, it probably should be queued for 3.1 and 3.0-stable. Comments and feedback would be greatly appreciated! Reported-by: Zach Pfeffer <zach.pfeffer@linaro.org> Signed-off-by: John Stultz <john.stultz@linaro.org>
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 6aeb363e63e..548338c2147 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -1698,6 +1698,8 @@ static int musb_gadget_pullup(struct usb_gadget *gadget, int is_on)
is_on = !!is_on;
+ pm_runtime_get_sync(musb->controller);
/* NOTE: this assumes we are sensing vbus; we'd rather
* not pullup unless the B-session is active.
@@ -1707,6 +1709,9 @@ static int musb_gadget_pullup(struct usb_gadget *gadget, int is_on)
musb_pullup(musb, is_on);
spin_unlock_irqrestore(&musb->lock, flags);
+ pm_runtime_put(musb->controller);
return 0;