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    Subject[ 25/85] usb: musb: am35xx: drop spurious unplugging a device
    Date
    3.6-stable review patch.  If anyone has any objections, please let me know.

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

    From: Stefano Babic <sbabic@denx.de>

    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@denx.de>
    CC: Felipe Balbi <balbi@ti.com>
    Tested-by: Dmitry Lifshitz <lifshitz@compulab.co.il>
    Tested-by: Igor Grinberg <grinberg@compulab.co.il>
    Signed-off-by: Felipe Balbi <balbi@ti.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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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