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 diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 405ea7a..68350aa 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -208,6 +208,25 @@ config ARC_PAGE_SIZE_4K endchoice +config ARC_COMPACT_IRQ_LEVELS + bool "ARCompact IRQ Priorities: High(2)/Low(1)" + default n + # Timer HAS to be high priority, for any other high priority config + select ARC_IRQ3_LV2 + +if ARC_COMPACT_IRQ_LEVELS + +config ARC_IRQ3_LV2 + bool + +config ARC_IRQ5_LV2 + bool + +config ARC_IRQ6_LV2 + bool + +endif + config ARC_FPU_SAVE_RESTORE bool "Enable FPU state persistence across context switch" default n diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h index 716f4f7..23ef2de 100644 --- a/arch/arc/include/asm/entry.h +++ b/arch/arc/include/asm/entry.h @@ -5,6 +5,12 @@ * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * + * Vineetg: March 2009 (Supporting 2 levels of Interrupts) + * Stack switching code can no longer reliably rely on the fact that + * if we are NOT in user mode, stack is switched to kernel mode. + * e.g. L2 IRQ interrupted a L1 ISR which had not yet completed + * it's prologue including stack switching from user mode + * * Vineetg: Aug 28th 2008: Bug #94984 * -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap * Normally CPU does this automatically, however when doing FAKE rtie, @@ -268,6 +274,33 @@ * assume SP is kernel mode SP. _NO_ need to do any stack switching */ +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS + /* However.... + * If Level 2 Interrupts enabled, we may end up with a corner case: + * 1. User Task executing + * 2. L1 IRQ taken, ISR starts (CPU auto-switched to KERNEL mode) + * 3. But before it could switch SP from USER to KERNEL stack + * a L2 IRQ "Interrupts" L1 + * Thay way although L2 IRQ happened in Kernel mode, stack is still + * not switched. + * To handle this, we may need to switch stack even if in kernel mode + * provided SP has values in range of USER mode stack ( < 0x7000_0000 ) + */ + brlo sp, VMALLOC_START, 88f + + /* TODO: vineetg: + * We need to be a bit more cautious here. What if a kernel bug in + * L1 ISR, caused SP to go whaco (some small value which looks like + * USER stk) and then we take L2 ISR. + * Above brlo alone would treat it as a valid L1-L2 sceanrio + * instead of shouting alound + * The only feasible way is to make sure this L2 happened in + * L1 prelogue ONLY i.e. ilink2 is less than a pre-set marker in + * L1 ISR before it switches stack + */ + +#endif + /* Save Pre Intr/Exception KERNEL MODE SP on kernel stack * safe-keeping not really needed, but it keeps the epilogue code * (SP restore) simpler/uniform. @@ -503,6 +536,42 @@ sub sp, sp, 4 .endm +.macro SAVE_ALL_INT2 + + /* TODO-vineetg: SMP we can't use global nor can we use + * SCRATCH0 as we do for int1 because while int1 is using + * it, int2 can come + */ + /* retsore original r9 , saved in sys_saved_r9 */ + ld r9, [@int2_saved_reg] + + /* now we are ready to save the remaining context :) */ + st orig_r8_IS_IRQ2, [sp, 8] /* Event Type */ + st 0, [sp, 4] /* orig_r0 , N/A for IRQ */ + SAVE_CALLER_SAVED + st.a r26, [sp, -4] /* gp */ + st.a fp, [sp, -4] + st.a blink, [sp, -4] + st.a ilink2, [sp, -4] + lr r9, [status32_l2] + st.a r9, [sp, -4] + st.a lp_count, [sp, -4] + lr r9, [lp_end] + st.a r9, [sp, -4] + lr r9, [lp_start] + st.a r9, [sp, -4] + lr r9, [bta_l2] + st.a r9, [sp, -4] + +#ifdef PT_REGS_CANARY + mov r9, 0xdeadbee2 + st r9, [sp, -4] +#endif + + /* move up by 1 word to "create" pt_regs->"stack_place_holder" */ + sub sp, sp, 4 +.endm + /*-------------------------------------------------------------- * Restore all registers used by interrupt handlers. * @@ -537,6 +606,32 @@ /* orig_r0 and orig_r8 skipped automatically */ .endm +.macro RESTORE_ALL_INT2 + add sp, sp, 4 /* hop over unused "pt_regs->stack_place_holder" */ + + ld.ab r9, [sp, 4] + sr r9, [bta_l2] + ld.ab r9, [sp, 4] + sr r9, [lp_start] + ld.ab r9, [sp, 4] + sr r9, [lp_end] + ld.ab r9, [sp, 4] + mov lp_count, r9 + ld.ab r9, [sp, 4] + sr r9, [status32_l2] + ld.ab r9, [sp, 4] + mov ilink2, r9 + ld.ab blink, [sp, 4] + ld.ab fp, [sp, 4] + ld.ab r26, [sp, 4] /* gp */ + RESTORE_CALLER_SAVED + + ld sp, [sp] /* restore original sp */ + /* orig_r0 and orig_r8 skipped automatically */ + +.endm + + /* Get CPU-ID of this core */ .macro GET_CPU_ID reg lr \reg, [identity] diff --git a/arch/arc/include/asm/irqflags.h b/arch/arc/include/asm/irqflags.h index 5cc1080..ccd8480 100644 --- a/arch/arc/include/asm/irqflags.h +++ b/arch/arc/include/asm/irqflags.h @@ -95,7 +95,11 @@ static inline long arch_local_save_flags(void) */ static inline int arch_irqs_disabled_flags(unsigned long flags) { - return !(flags & (STATUS_E1_MASK)); + return !(flags & (STATUS_E1_MASK +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS + | STATUS_E2_MASK +#endif + )); } static inline int arch_irqs_disabled(void) diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 76697ae..e33a0bf 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -31,6 +31,8 @@ * exception. Thus FAKE RTIE needed in low level Priv-Violation handler. * Instr Error could also cause similar scenario, so same there as well. * + * Vineetg: March 2009 (Supporting 2 levels of Interrupts) + * * Vineetg: Aug 28th 2008: Bug #94984 * -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap * Normally CPU does this automatically, however when doing FAKE rtie, @@ -96,13 +98,25 @@ VECTOR mem_service ; 0x8, Mem exception (0x1) VECTOR instr_service ; 0x10, Instrn Error (0x2) ; ******************** Device ISRs ********************** +#ifdef CONFIG_ARC_IRQ3_LV2 +VECTOR handle_interrupt_level2 +#else VECTOR handle_interrupt_level1 +#endif VECTOR handle_interrupt_level1 +#ifdef CONFIG_ARC_IRQ5_LV2 +VECTOR handle_interrupt_level2 +#else VECTOR handle_interrupt_level1 +#endif +#ifdef CONFIG_ARC_IRQ6_LV2 +VECTOR handle_interrupt_level2 +#else VECTOR handle_interrupt_level1 +#endif .rept 25 VECTOR handle_interrupt_level1 ; Other devices @@ -139,6 +153,17 @@ VECTOR reserved ; Reserved Exceptions int1_saved_reg: .zero 4 +/* Each Interrupt level needs it's own scratch */ +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS + + .section .data ; NOT .global + .type int2_saved_reg, @object + .size int2_saved_reg, 4 +int2_saved_reg: + .zero 4 + +#endif + ; --------------------------------------------- .section .text, "ax",@progbits @@ -152,6 +177,55 @@ reserved: ; processor restart ;##################### Interrupt Handling ############################## +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS +; --------------------------------------------- +; Level 2 ISR: Can interrupt a Level 1 ISR +; --------------------------------------------- +ARC_ENTRY handle_interrupt_level2 + + ; TODO-vineetg for SMP this wont work + ; free up r9 as scratchpad + st r9, [@int2_saved_reg] + + ;Which mode (user/kernel) was the system in when intr occured + lr r9, [status32_l2] + + SWITCH_TO_KERNEL_STK + SAVE_ALL_INT2 + + ;------------------------------------------------------ + ; if L2 IRQ interrupted a L1 ISR, disable preemption + ;------------------------------------------------------ + + ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs) + bbit0 r9, STATUS_A1_BIT, 1f ; L1 not active when L2 IRQ, so normal + + ; A1 is set in status32_l2 + ; bump thread_info->preempt_count (Disable preemption) + GET_CURR_THR_INFO_FROM_SP r10 + ld r9, [r10, THREAD_INFO_PREEMPT_COUNT] + add r9, r9, 1 + st r9, [r10, THREAD_INFO_PREEMPT_COUNT] + +1: + ;------------------------------------------------------ + ; setup params for Linux common ISR and invoke it + ;------------------------------------------------------ + lr r0, [icause2] + and r0, r0, 0x1f + + bl.d @arch_do_IRQ + mov r1, sp + + mov r8,0x2 + sr r8, [AUX_IRQ_LV12] ; clear bit in Sticky Status Reg + + b ret_from_exception + +ARC_EXIT handle_interrupt_level2 + +#endif + ; --------------------------------------------- ; Level 1 ISR ; --------------------------------------------- @@ -619,6 +693,49 @@ restore_regs : not_exception: +#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS + + bbit0 r10, STATUS_A2_BIT, not_level2_interrupt + + ;------------------------------------------------------------------ + ; if L2 IRQ interrupted a L1 ISR, we'd disbaled preemption earlier + ; so that sched doesnt move to new task, causing L1 to be delayed + ; undeterministically. Now that we've achieved that, lets reset + ; things to what they were, before returning from L2 context + ;---------------------------------------------------------------- + + ld r9, [sp, PT_orig_r8] ; get orig_r8 to make sure it is + brne r9, orig_r8_IS_IRQ2, 149f ; infact a L2 ISR ret path + + ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs) + bbit0 r9, STATUS_A1_BIT, 149f ; L1 not active when L2 IRQ, so normal + + ; A1 is set in status32_l2 + ; decrement thread_info->preempt_count (re-enable preemption) + GET_CURR_THR_INFO_FROM_SP r10 + ld r9, [r10, THREAD_INFO_PREEMPT_COUNT] + + ; paranoid check, given A1 was active when A2 happened, preempt count + ; must not be 0 beccause we would have incremented it. + ; If this does happen we simply HALT as it means a BUG !!! + cmp r9, 0 + bnz 2f + flag 1 + +2: + sub r9, r9, 1 + st r9, [r10, THREAD_INFO_PREEMPT_COUNT] + +149: + ;return from level 2 + RESTORE_ALL_INT2 +debug_marker_l2: + rtie + +not_level2_interrupt: + +#endif + bbit0 r10, STATUS_A1_BIT, not_level1_interrupt ;return from level 1 diff --git a/arch/arc/kernel/irq.c b/arch/arc/kernel/irq.c index 3c18e66..ca70894 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 v0.10.2