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    Subject[PATCH] tty: omap-serial: fix boot hang by converting to use a threaded IRQ handler (was Re: [PATCH] irq: always set IRQF_ONESHOT if no primary handler is specified)

    Convert the omap-serial hardirq handler to a threaded IRQ handler. Without
    this patch, OMAP boards which use the on-board OMAP UARTs and the
    omap-serial driver will not boot to userspace after commit
    f3637a5f2e2eb391ff5757bc83fb5de8f9726464 ("irq: Always set IRQF_ONESHOT if
    no primary handler is specified"). Enabling CONFIG_DEBUG_SHIRQ reveals
    'IRQ handler type mismatch' errors:

    IRQ handler type mismatch for IRQ 74
    current handler: serial idle
    [<c001b124>] (unwind_backtrace+0x0/0xf0) from [<c009c900>] (__setup_irq+0x42c/0x464)
    [<c009c900>] (__setup_irq+0x42c/0x464) from [<c009ca08>] (request_threaded_irq+0xd0/0x148)
    [<c009ca08>] (request_threaded_irq+0xd0/0x148) from [<c029d398>] (serial_omap_startup+0x30/0x2dc)
    [<c029d398>] (serial_omap_startup+0x30/0x2dc) from [<c0295a38>] (uart_startup+0x5c/0x1ac)


    It turns out that the omap-serial code used one threaded IRQ
    handler[1][2] and one non-threaded IRQ handler[3] that shared the same
    IRQ. During the 3.1-rc series, a patch was merged[4] that caused
    IRQF_ONESHOT to be set on the threaded handler, but the non-threaded
    handler did not have IRQF_ONESHOT set. Since interrupt handlers
    that share the same IRQ must also share the presence or absence of
    IRQF_ONESHOT[5], this new commit caused a mismatch that prevented the
    non-threaded IRQ from registering.

    Fix by converting the non-threaded IRQ handler in omap-serial.c to a
    threaded IRQ handler. Ideally we would not have to make this type of
    change during the -rc series, but the commit that caused this behavior
    was itself merged between v3.1-rc2 and v3.1-rc3. In the long term, it
    would be good to get rid of the shared IRQ handler hack in

    This change has been boot-tested on OMAP3530 BeagleBoard and
    OMAP4430ES2 PandaBoard, and static suspend has been lightly tested on
    the BeagleBoard.

    Pantelis Antoniou <> originally reported
    the boot failure.

    1. arch/arm/mach-omap2/serial.c line 550, as of Linux v3.1-rc3.;a=blob;f=arch/arm/mach-omap2/serial.c;h=466fc722fa0f39f03b8d93cf84e4dae4f57fd029;hb=fcb8ce5cfe30ca9ca5c9a79cdfe26d1993e65e0c#l550

    2. arch/arm/mach-omap2/serial.c line 563, as of Linux v3.1-rc3.;a=blob;f=arch/arm/mach-omap2/serial.c;h=466fc722fa0f39f03b8d93cf84e4dae4f57fd029;hb=fcb8ce5cfe30ca9ca5c9a79cdfe26d1993e65e0c#l563

    3. drivers/tty/serial/omap-serial.c line 464, as of Linux v3.1-rc3.;a=blob;f=drivers/tty/serial/omap-serial.c;h=c37df8d0fa2819261dffccc5bc4d0180b9531f49;hb=fcb8ce5cfe30ca9ca5c9a79cdfe26d1993e65e0c#l464

    4. Commit f3637a5f2e2eb391ff5757bc83fb5de8f9726464 ("irq: Always set
    IRQF_ONESHOT if no primary handler is specified")

    5. Gleixner, Thomas. _[patch 2/5] genirq: Allow shared oneshot

    Signed-off-by: Paul Walmsley <>
    Cc: Pantelis Antoniou <>
    Cc: Govindraj.R <>
    Cc: Kevin Hilman <>
    Cc: Thomas Gleixner <>
    Cc: Sebastian Andrzej Siewior <>
    drivers/tty/serial/omap-serial.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
    index c37df8d..e83a769 100644
    --- a/drivers/tty/serial/omap-serial.c
    +++ b/drivers/tty/serial/omap-serial.c
    @@ -461,8 +461,8 @@ static int serial_omap_startup(struct uart_port *port)
    * Allocate the IRQ
    - retval = request_irq(up->port.irq, serial_omap_irq, up->port.irqflags,
    - up->name, up);
    + retval = request_threaded_irq(up->port.irq, NULL, serial_omap_irq,
    + up->port.irqflags, up->name, up);
    if (retval)
    return retval;


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