[POWERPC] Update wait_state_cycles in the VPA

The hypervisor can look at the value in the wait_state_cycles field of
the VPA for an estimate of how busy dedicated processors are.
Currently, as the kernel never touches this field, we appear to be
100% busy.  This records the duration the kernel is in powersave and
passes that to the HV to provide a reasonable indication of
utilisation.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index fdb9b1c..90555a3 100644 (file)
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -393,6 +393,7 @@ static void pseries_dedicated_idle_sleep(void)
 { 
        unsigned int cpu = smp_processor_id();
        unsigned long start_snooze;
+       unsigned long in_purr, out_purr;
 
        /*
         * Indicate to the HV that we are idle. Now would be
@@ -400,6 +401,7 @@ static void pseries_dedicated_idle_sleep(void)
         */
        get_lppaca()->idle = 1;
        get_lppaca()->donate_dedicated_cpu = 1;
+       in_purr = mfspr(SPRN_PURR);
 
        /*
         * We come in with interrupts disabled, and need_resched()
@@ -432,6 +434,8 @@ static void pseries_dedicated_idle_sleep(void)
 
 out:
        HMT_medium();
+       out_purr = mfspr(SPRN_PURR);
+       get_lppaca()->wait_state_cycles += out_purr - in_purr;
        get_lppaca()->donate_dedicated_cpu = 0;
        get_lppaca()->idle = 0;
 }