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>
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]