• Marc Zyngier's avatar
    genirq: Add support for per-cpu dev_id interrupts · 31d9d9b6
    Marc Zyngier authored
    The ARM GIC interrupt controller offers per CPU interrupts (PPIs),
    which are usually used to connect local timers to each core. Each CPU
    has its own private interface to the GIC, and only sees the PPIs that
    are directly connect to it.
    
    While these timers are separate devices and have a separate interrupt
    line to a core, they all use the same IRQ number.
    
    For these devices, request_irq() is not the right API as it assumes
    that an IRQ number is visible by a number of CPUs (through the
    affinity setting), but makes it very awkward to express that an IRQ
    number can be handled by all CPUs, and yet be a different interrupt
    line on each CPU, requiring a different dev_id cookie to be passed
    back to the handler.
    
    The *_percpu_irq() functions is designed to overcome these
    limitations, by providing a per-cpu dev_id vector:
    
    int request_percpu_irq(unsigned int irq, irq_handler_t handler,
    		   const char *devname, void __percpu *percpu_dev_id);
    void free_percpu_irq(unsigned int, void __percpu *);
    int setup_percpu_irq(unsigned int irq, struct irqaction *new);
    void remove_percpu_irq(unsigned int irq, struct irqaction *act);
    void enable_percpu_irq(unsigned int irq);
    void disable_percpu_irq(unsigned int irq);
    
    The API has a number of limitations:
    - no interrupt sharing
    - no threading
    - common handler across all the CPUs
    
    Once the interrupt is requested using setup_percpu_irq() or
    request_percpu_irq(), it must be enabled by each core that wishes its
    local interrupt to be delivered.
    
    Based on an initial patch by Thomas Gleixner.
    Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    Cc: linux-arm-kernel@lists.infradead.org
    Link: http://lkml.kernel.org/r/1316793788-14500-2-git-send-email-marc.zyngier@arm.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    31d9d9b6
irqdesc.c 11 KB