[MIPS] SMTC: Instant IPI replay.

SMTC pseudo-interrupts between TCs are deferred and queued if the target
TC is interrupt-inhibited (IXMT). In the first SMTC prototypes, these
queued IPIs were serviced on return to user mode, or on entry into the
kernel idle loop. The INSTANT_REPLAY option dispatches them as part of
local_irq_restore() processing, which adds runtime overhead (hence the
option to turn it off), but ensures that IPIs are handled promptly even
under heavy I/O interrupt load.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index fd2ff0698a85..bbd386f572d9 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1568,6 +1568,20 @@ config MIPS_MT_FPAFF
         depends on MIPS_MT
         default y
 
+config MIPS_MT_SMTC_INSTANT_REPLAY
+        bool "Low-latency Dispatch of Deferred SMTC IPIs"
+        depends on MIPS_MT_SMTC
+        default y
+        help
+          SMTC pseudo-interrupts between TCs are deferred and queued
+          if the target TC is interrupt-inhibited (IXMT). In the first
+          SMTC prototypes, these queued IPIs were serviced on return
+          to user mode, or on entry into the kernel idle loop. The
+          INSTANT_REPLAY option dispatches them as part of local_irq_restore()
+          processing, which adds runtime overhead (hence the option to turn
+          it off), but ensures that IPIs are handled promptly even under
+          heavy I/O interrupt load.
+
 config MIPS_VPE_LOADER_TOM
         bool "Load VPE program into memory hidden from linux"
         depends on MIPS_VPE_LOADER