diff options
| -rw-r--r-- | drivers/irqchip/irq-armada-370-xp.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/drivers/irqchip/irq-armada-370-xp.c b/drivers/irqchip/irq-armada-370-xp.c index 76147dfdfccd..1f7dea613d15 100644 --- a/drivers/irqchip/irq-armada-370-xp.c +++ b/drivers/irqchip/irq-armada-370-xp.c @@ -34,6 +34,86 @@ #include <asm/smp_plat.h> #include <asm/mach/irq.h> +/* + * Overall diagram of the Armada XP interrupt controller: + * + * To CPU 0 To CPU 1 + * + * /\ /\ + * || || + * +---------------+ +---------------+ + * | | | | + * | per-CPU | | per-CPU | + * | mask/unmask | | mask/unmask | + * | CPU0 | | CPU1 | + * | | | | + * +---------------+ +---------------+ + * /\ /\ + * || || + * \\_______________________// + * || + * +-------------------+ + * | | + * | Global interrupt | + * | mask/unmask | + * | | + * +-------------------+ + * /\ + * || + * interrupt from + * device + * + * The "global interrupt mask/unmask" is modified using the + * ARMADA_370_XP_INT_SET_ENABLE_OFFS and + * ARMADA_370_XP_INT_CLEAR_ENABLE_OFFS registers, which are relative + * to "main_int_base". + * + * The "per-CPU mask/unmask" is modified using the + * ARMADA_370_XP_INT_SET_MASK_OFFS and + * ARMADA_370_XP_INT_CLEAR_MASK_OFFS registers, which are relative to + * "per_cpu_int_base". This base address points to a special address, + * which automatically accesses the registers of the current CPU. + * + * The per-CPU mask/unmask can also be adjusted using the global + * per-interrupt ARMADA_370_XP_INT_SOURCE_CTL register, which we use + * to configure interrupt affinity. + * + * Due to this model, all interrupts need to be mask/unmasked at two + * different levels: at the global level and at the per-CPU level. + * + * This driver takes the following approach to deal with this: + * + * - For global interrupts: + * + * At ->map() time, a global interrupt is unmasked at the per-CPU + * mask/unmask level. It is therefore unmasked at this level for + * the current CPU, running the ->map() code. This allows to have + * the interrupt unmasked at this level in non-SMP + * configurations. In SMP configurations, the ->set_affinity() + * callback is called, which using the + * ARMADA_370_XP_INT_SOURCE_CTL() readjusts the per-CPU mask/unmask + * for the interrupt. + * + * The ->mask() and ->unmask() operations only mask/unmask the + * interrupt at the "global" level. + * + * So, a global interrupt is enabled at the per-CPU level as soon + * as it is mapped. At run time, the masking/unmasking takes place + * at the global level. + * + * - For per-CPU interrupts + * + * At ->map() time, a per-CPU interrupt is unmasked at the global + * mask/unmask level. + * + * The ->mask() and ->unmask() operations mask/unmask the interrupt + * at the per-CPU level. + * + * So, a per-CPU interrupt is enabled at the global level as soon + * as it is mapped. At run time, the masking/unmasking takes place + * at the per-CPU level. + */ + /* Registers relative to main_int_base */ #define ARMADA_370_XP_INT_CONTROL (0x00) #define ARMADA_370_XP_SW_TRIG_INT_OFFS (0x04) |