MN10300: Make the FPU operate in non-lazy mode under SMP

Make the FPU operate in non-lazy mode under SMP so that when the process that
is currently using the FPU migrates to a different CPU, we don't have to ping
its previous CPU to flush the FPU context.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/mn10300/Kconfig b/arch/mn10300/Kconfig
index 7bd920b1c06f..a1f334ce0a36 100644
--- a/arch/mn10300/Kconfig
+++ b/arch/mn10300/Kconfig
@@ -140,6 +140,21 @@ config FPU
         default y
         depends on MN10300_PROC_MN103E010
 
+config LAZY_SAVE_FPU
+        bool "Save FPU state lazily"
+        default y
+        depends on FPU && !SMP
+        help
+          Enable this to be lazy in the saving of the FPU state to the owning
+          task's thread struct.  This is useful if most tasks on the system
+          don't use the FPU as only those tasks that use it will pass it
+          between them, and the state needn't be saved for a task that isn't
+          using it.
+
+          This can't be so easily used on SMP as the process that owns the FPU
+          state on a CPU may be currently running on another CPU, so for the
+          moment, it is disabled.
+
 source "arch/mn10300/mm/Kconfig.cache"
 
 config MN10300_TLB_USE_PIDR