• Nicolas Pitre's avatar
    [ARM] 5401/1: Orion: fix edge triggered GPIO interrupt support · fd4b9b36
    Nicolas Pitre authored
    The GPIO interrupts can be configured as either level triggered or edge
    triggered, with a default of level triggered.  When an edge triggered
    interrupt is requested, the gpio_irq_set_type method is called which
    currently switches the given IRQ descriptor between two struct irq_chip
    instances: orion_gpio_irq_level_chip and orion_gpio_irq_edge_chip. This
    happens via __setup_irq() which also calls irq_chip_set_defaults() to
    assign default methods to uninitialized ones.  The problem is that
    irq_chip_set_defaults() is called before the irq_chip reference is
    switched, leaving the new irq_chip (orion_gpio_irq_edge_chip in this
    case) with uninitialized methods such as chip->startup() causing a kernel
    oops.
    
    Many solutions are possible, such as making irq_chip_set_defaults() global
    and calling it from gpio_irq_set_type(), or calling __irq_set_trigger()
    before irq_chip_set_defaults() in __setup_irq().  But those require
    modifications to the generic IRQ code which might have adverse effect on
    other architectures, and that would still be a fragile arrangement.
    Manually copying the missing methods from within gpio_irq_set_type()
    would be really ugly and it would break again the day new methods with
    automatic defaults are added.
    
    A better solution is to have a single irq_chip instance which can deal
    with both edge and level triggered interrupts.  It is also a good idea
    to switch the IRQ handler instead, as the edge IRQ handler allows for
    one edge IRQ event to be queued as the IRQ is actually masked only when
    that second IRQ is received, at which point the hardware can queue an
    additional IRQ event, making edge triggered interrupts a bit more
    reliable.
    Tested-by: default avatarMartin Michlmayr <tbm@cyrius.com>
    Signed-off-by: default avatarNicolas Pitre <nico@marvell.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    fd4b9b36
gpio.c 8.71 KB