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    Subject[PATCH 4.11 098/114] serial: omap: fix runtime-pm handling on unbind
    Date
    4.11-stable review patch.  If anyone has any objections, please let me know.

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

    From: Johan Hovold <johan@kernel.org>

    commit 099bd73dc17ed77aa8c98323e043613b6e8f54fc upstream.

    An unbalanced and misplaced synchronous put was used to suspend the
    device on driver unbind, something which with a likewise misplaced
    pm_runtime_disable leads to external aborts when an open port is being
    removed.

    Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa024010
    ...
    [<c046e760>] (serial_omap_set_mctrl) from [<c046a064>] (uart_update_mctrl+0x50/0x60)
    [<c046a064>] (uart_update_mctrl) from [<c046a400>] (uart_shutdown+0xbc/0x138)
    [<c046a400>] (uart_shutdown) from [<c046bd2c>] (uart_hangup+0x94/0x190)
    [<c046bd2c>] (uart_hangup) from [<c045b760>] (__tty_hangup+0x404/0x41c)
    [<c045b760>] (__tty_hangup) from [<c045b794>] (tty_vhangup+0x1c/0x20)
    [<c045b794>] (tty_vhangup) from [<c046ccc8>] (uart_remove_one_port+0xec/0x260)
    [<c046ccc8>] (uart_remove_one_port) from [<c046ef4c>] (serial_omap_remove+0x40/0x60)
    [<c046ef4c>] (serial_omap_remove) from [<c04845e8>] (platform_drv_remove+0x34/0x4c)

    Fix this up by resuming the device before deregistering the port and by
    suspending and disabling runtime pm only after the port has been
    removed.

    Also make sure to disable autosuspend before disabling runtime pm so
    that the usage count is balanced and device actually suspended before
    returning.

    Note that due to a negative autosuspend delay being set in probe, the
    unbalanced put would actually suspend the device on first driver unbind,
    while rebinding and again unbinding would result in a negative
    power.usage_count.

    Fixes: 7e9c8e7dbf3b ("serial: omap: make sure to suspend device before remove")
    Cc: Felipe Balbi <balbi@kernel.org>
    Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
    Signed-off-by: Johan Hovold <johan@kernel.org>
    Acked-by: Tony Lindgren <tony@atomide.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/tty/serial/omap-serial.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/drivers/tty/serial/omap-serial.c
    +++ b/drivers/tty/serial/omap-serial.c
    @@ -1780,9 +1780,13 @@ static int serial_omap_remove(struct pla
    {
    struct uart_omap_port *up = platform_get_drvdata(dev);

    + pm_runtime_get_sync(up->dev);
    +
    + uart_remove_one_port(&serial_omap_reg, &up->port);
    +
    + pm_runtime_dont_use_autosuspend(up->dev);
    pm_runtime_put_sync(up->dev);
    pm_runtime_disable(up->dev);
    - uart_remove_one_port(&serial_omap_reg, &up->port);
    pm_qos_remove_request(&up->pm_qos_request);
    device_init_wakeup(&dev->dev, false);


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