[ 25/85] usb: musb: am35xx: drop spurious unplugging a device

[Greg Kroah-Hartman]

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefano Babic <sbabic@xxxxxxx>

commit 6ff1f3d3bd7c69c62ca5773b1b684bce42eff06a upstream.

On AM3517, tx and rx interrupt are detected together with
the disconnect event. This generates a kernel panic in musb_interrupt,
because rx / tx are handled after disconnect.
This issue was seen on a Technexion's TAM3517 SOM. Unplugging a device,
tx / rx interrupts together with disconnect are detected. This brings
to kernel panic like this:

[   68.526153] Unable to handle kernel NULL pointer dereference at virtual address 00000011
[   68.534698] pgd = c0004000
[   68.537536] [00000011] *pgd=00000000
[   68.541351] Internal error: Oops: 17 [#1] ARM
[   68.545928] Modules linked in:
[   68.549163] CPU: 0    Not tainted  (3.6.0-rc5-00020-g9e05905 #178)
[   68.555694] PC is at rxstate+0x8/0xdc
[   68.559539] LR is at musb_interrupt+0x98/0x858
[   68.564239] pc : [<c035cd88>]    lr : [<c035af1c>]    psr: 40000193
[   68.564239] sp : ce83fb40  ip : d0906410  fp : 00000000
[   68.576293] r10: 00000000  r9 : cf3b0e40  r8 : 00000002
[   68.581817] r7 : 00000019  r6 : 00000001  r5 : 00000001  r4 : 000000d4
[   68.588684] r3 : 00000000  r2 : 00000000  r1 : ffffffcc  r0 : cf23c108
[   68.595550] Flags: nZcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment ke

Note: this behavior is not seen with a USB hub, while it is
easy to reproduce connecting a USB-pen directly to the USB-A of
the board.

Drop tx / rx interrupts if disconnect is detected.

Signed-off-by: Stefano Babic <sbabic@xxxxxxx>
CC: Felipe Balbi <balbi@xxxxxx>
Tested-by: Dmitry Lifshitz <lifshitz@xxxxxxxxxxxxxx>
Tested-by: Igor Grinberg <grinberg@xxxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/musb/am35x.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/usb/musb/am35x.c
+++ b/drivers/usb/musb/am35x.c
@@ -312,6 +312,12 @@ static irqreturn_t am35x_musb_interrupt(
 		ret = IRQ_HANDLED;
 	}
 
+	/* Drop spurious RX and TX if device is disconnected */
+	if (musb->int_usb & MUSB_INTR_DISCONNECT) {
+		musb->int_tx = 0;
+		musb->int_rx = 0;
+	}
+
 	if (musb->int_tx || musb->int_rx || musb->int_usb)
 		ret |= musb_interrupt(musb);
 


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