• Doug Berger's avatar
    gpio: brcmstb: implement suspend/resume/shutdown · 4714221b
    Doug Berger authored
    This commit corrects problems with the previous wake implementation
    by implementing suspend and resume power management operations and
    the driver shutdown operation.
    
    Wake masks are used to keep track of which GPIO should wake the
    device.  On suspend the GPIO state is saved and the possible wakeup
    sources are explicitly unmasked in the hardware. Non-wakeup sources
    are explicitly masked so IRQCHIP_MASK_ON_SUSPEND is no longer
    necessary.  The saved state of the GPIO is restored upon resume.
    It is important not to write to the GPIO status register since this
    has the effect of clearing bits.  The status register is explicitly
    removed from the register save and restore to ensure this.
    
    The shutdown operation allows the hardware to be put into the same
    quiesced state as the suspend operation and removes the need for
    the reboot notifier.
    
    Unfortunately, there appears to be some confusion about whether
    a pending disabled wake interrupt should wake the system. If a wake
    capable interrupt is disabled using the default "lazy disable"
    behavior and it is triggered before the suspend_device_irq call
    the interrupt hardware will be acknowledged by mask_ack_irq and the
    IRQS_PENDING flag is added to its state. However, the IRQS_PENDING
    flag of wake interrupts is not checked to prevent the transition to
    suspend and the hardware has been acked which prevents its wakeup.
    If the lazy disabled interrupt is triggered after the call to
    suspend_device_irqs then the wakeup logic will abort the suspend.
    The irq_disable method is defined by this GPIO driver to prevent
    lazy disable so that the pending hardware state remains asserted
    allowing the hardware to wake and providing a consistent behavior.
    
    In addition, the IRQ_DISABLE_UNLAZY flag is set for the non-wake
    parent interrupt as a convenience to prevent the need to add code
    to the brcmstb_gpio_irq_handler to support "lazy disable" of the
    non-wake parent interrupt when it is disabled during suspend and
    resume. Chained interrupt parents are not normally disabled, but
    these GPIO devices have different parent interrupts for wake and
    non-wake handling. It is convenient to mask the non-wake parent
    when suspending to preserve the hardware state for proper wakeup
    accounting when the driver is resumed.
    Signed-off-by: 's avatarDoug Berger <opendmb@gmail.com>
    Acked-by: 's avatarGregory Fong <gregory.0xf0@gmail.com>
    Reviewed-by: 's avatarFlorian Fainelli <f.fainelli@gmail.com>
    Signed-off-by: 's avatarLinus Walleij <linus.walleij@linaro.org>
    4714221b