[PATCH-v3 5/7] score/sparc: Add comment on icache flush after trap table update

[Daniel Cederman]

Changes to the trap table might be missed by other cores.
If the system state is up, the other cores can be notified
using SMP messages that they need to flush their icache.
If the up state has not been reached there is no need to
notify other cores. They will do an automatic flush of the
icache just after entering the up state, but before enabling
interrupts. Cache invalidation is required for both single
and multiprocessor systems.
---
 cpukit/score/cpu/sparc/cpu.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/cpukit/score/cpu/sparc/cpu.c b/cpukit/score/cpu/sparc/cpu.c
index c616de4..80aea64 100644
--- a/cpukit/score/cpu/sparc/cpu.c
+++ b/cpukit/score/cpu/sparc/cpu.c
@@ -210,10 +210,21 @@ void _CPU_ISR_install_raw_handler(
     (u32_handler & HIGH_BITS_MASK) >> HIGH_BITS_SHIFT;
   slot->jmp_to_low_of_handler_plus_l4 |= (u32_handler & LOW_BITS_MASK);
 
-  /* need to flush icache after this !!! */
-
+  /*
+   * There is no instruction cache snooping, so we need to invalidate
+   * the instruction cache to make sure that the processor sees the
+   * changes to the trap table. This step is required on both single-
+   * and multiprocessor systems. 
+   *
+   * In a SMP configuration a change to the trap table might be
+   * missed by other cores. If the system state is up, the other
+   * cores can be notified using SMP messages that they need to
+   * flush their icache. If the up state has not been reached
+   * there is no need to notify other cores. They will do an
+   * automatic flush of the icache just after entering the up
+   * state, but before enabling interrupts.
+   */
   rtems_cache_invalidate_entire_instruction();
-
 }
 
 void _CPU_ISR_install_vector(
-- 
1.7.9.5