From 4788a5942bc896803c87005be8c6dd14c373a2d3 Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Fri, 18 Jan 2013 15:12:22 +0530 Subject: ARC: Support for high priority interrupts in the in-core intc There is a bit of hack/kludge right now where we disable preemption if a L2 (High prio) IRQ is taken while L1 (Low prio) is active. Need to revisit this Signed-off-by: Vineet Gupta --- arch/arc/kernel/irq.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 103 insertions(+), 1 deletion(-) (limited to 'arch/arc/kernel/irq.c') diff --git a/arch/arc/kernel/irq.c b/arch/arc/kernel/irq.c index 3c18e66386c7..ca70894e2309 100644 --- a/arch/arc/kernel/irq.c +++ b/arch/arc/kernel/irq.c @@ -23,15 +23,32 @@ * what it does ? * -setup Vector Table Base Reg - in case Linux not linked at 0x8000_0000 * -Disable all IRQs (on CPU side) + * -Optionally, setup the High priority Interrupts as Level 2 IRQs */ void __init arc_init_IRQ(void) { - int level_mask = level_mask; + int level_mask = 0; write_aux_reg(AUX_INTR_VEC_BASE, _int_vec_base_lds); /* Disable all IRQs: enable them as devices request */ write_aux_reg(AUX_IENABLE, 0); + + /* setup any high priority Interrupts (Level2 in ARCompact jargon) */ +#ifdef CONFIG_ARC_IRQ3_LV2 + level_mask |= (1 << 3); +#endif +#ifdef CONFIG_ARC_IRQ5_LV2 + level_mask |= (1 << 5); +#endif +#ifdef CONFIG_ARC_IRQ6_LV2 + level_mask |= (1 << 6); +#endif + + if (level_mask) { + pr_info("Level-2 interrupts bitset %x\n", level_mask); + write_aux_reg(AUX_IRQ_LEV, level_mask); + } } /* @@ -141,6 +158,90 @@ int __init get_hw_config_num_irq(void) return 0; } +/* + * arch_local_irq_enable - Enable interrupts. + * + * 1. Explicitly called to re-enable interrupts + * 2. Implicitly called from spin_unlock_irq, write_unlock_irq etc + * which maybe in hard ISR itself + * + * Semantics of this function change depending on where it is called from: + * + * -If called from hard-ISR, it must not invert interrupt priorities + * e.g. suppose TIMER is high priority (Level 2) IRQ + * Time hard-ISR, timer_interrupt( ) calls spin_unlock_irq several times. + * Here local_irq_enable( ) shd not re-enable lower priority interrupts + * -If called from soft-ISR, it must re-enable all interrupts + * soft ISR are low prioity jobs which can be very slow, thus all IRQs + * must be enabled while they run. + * Now hardware context wise we may still be in L2 ISR (not done rtie) + * still we must re-enable both L1 and L2 IRQs + * Another twist is prev scenario with flow being + * L1 ISR ==> interrupted by L2 ISR ==> L2 soft ISR + * here we must not re-enable Ll as prev Ll Interrupt's h/w context will get + * over-written (this is deficiency in ARC700 Interrupt mechanism) + */ + +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS /* Complex version for 2 IRQ levels */ + +void arch_local_irq_enable(void) +{ + + unsigned long flags; + flags = arch_local_save_flags(); + + /* Allow both L1 and L2 at the onset */ + flags |= (STATUS_E1_MASK | STATUS_E2_MASK); + + /* Called from hard ISR (between irq_enter and irq_exit) */ + if (in_irq()) { + + /* If in L2 ISR, don't re-enable any further IRQs as this can + * cause IRQ priorities to get upside down. e.g. it could allow + * L1 be taken while in L2 hard ISR which is wrong not only in + * theory, it can also cause the dreaded L1-L2-L1 scenario + */ + if (flags & STATUS_A2_MASK) + flags &= ~(STATUS_E1_MASK | STATUS_E2_MASK); + + /* Even if in L1 ISR, allowe Higher prio L2 IRQs */ + else if (flags & STATUS_A1_MASK) + flags &= ~(STATUS_E1_MASK); + } + + /* called from soft IRQ, ideally we want to re-enable all levels */ + + else if (in_softirq()) { + + /* However if this is case of L1 interrupted by L2, + * re-enabling both may cause whaco L1-L2-L1 scenario + * because ARC700 allows level 1 to interrupt an active L2 ISR + * Thus we disable both + * However some code, executing in soft ISR wants some IRQs + * to be enabled so we re-enable L2 only + * + * How do we determine L1 intr by L2 + * -A2 is set (means in L2 ISR) + * -E1 is set in this ISR's pt_regs->status32 which is + * saved copy of status32_l2 when l2 ISR happened + */ + struct pt_regs *pt = get_irq_regs(); + if ((flags & STATUS_A2_MASK) && pt && + (pt->status32 & STATUS_A1_MASK)) { + /*flags &= ~(STATUS_E1_MASK | STATUS_E2_MASK); */ + flags &= ~(STATUS_E1_MASK); + } + } + + arch_local_irq_restore(flags); +} + +#else /* ! CONFIG_ARC_COMPACT_IRQ_LEVELS */ + +/* + * Simpler version for only 1 level of interrupt + * Here we only Worry about Level 1 Bits + */ void arch_local_irq_enable(void) { unsigned long flags; @@ -158,4 +259,5 @@ void arch_local_irq_enable(void) flags |= (STATUS_E1_MASK | STATUS_E2_MASK); arch_local_irq_restore(flags); } +#endif EXPORT_SYMBOL(arch_local_irq_enable); -- cgit v1.2.3