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 <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-01-18 15:12:22 +05:30
parent 769bc1fd7b
commit 4788a5942b
5 changed files with 339 additions and 2 deletions

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@ -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

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@ -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]

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@ -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)

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@ -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

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@ -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);