Moderately recent ARM interrupt controllers can use a "split mode" EOI, where instead of just using a single write to notify the controller of the end of interrupt, uses the following: - priority-drop: the interrupt is still active, but other interrupts can now be taken - deactivate: the interrupt is not active anymore, and can be taken again.
This makes it very useful for threaded interrupts, as it avoids the usual mask/unmask dance (and has the potential of being more efficient on ARM, as it is using the CPU interface instead of the global distributor, specially with the use of virtualization). To implement this, a new optional irqchip method is added (irq_priority_drop). The usual irq_eoi is expected to implement the deactivate method. Non threaded interrupts are using these two callbacks back to back, but threaded ones only perform the irq_priority_drop call in the interrupt context, leaving the irq_eoi call to the thread context (which are expected to use the IRQCHIP_EOI_THREADED flag). I've tried to keep the changes as simple as possible, but I'm afraid it might be too simple (I'm basically considering that a a irq_desc with the IRQS_ONESHOT flag is a threaded interrupt, which might not alwayd be true). This has been tested on a dual Cortex-A7 board, with the ahci driver using a threaded interrupt handler. Patches based on my irq/irqchip_state branch previously posted, and also available at: git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/priority_drop Marc Zyngier (3): genirq: Add support for priority-drop/deactivate interrupt controllers irqchip: GIC: Convert to EOImode == 1 irqchip: GICv3: Convert to EOImode == 1 drivers/irqchip/irq-gic-v3.c | 30 ++++++++++++++++-- drivers/irqchip/irq-gic.c | 64 ++++++++++++++++++++++++++++++++++---- include/linux/irq.h | 1 + include/linux/irqchip/arm-gic-v3.h | 10 ++++++ include/linux/irqchip/arm-gic.h | 4 +++ kernel/irq/chip.c | 53 +++++++++++++++++++++---------- 6 files changed, 138 insertions(+), 24 deletions(-) -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
