intel_idle: allow sparse sub-state numbering, for Bay Trail

Like acpi_idle, intel_idle compared sub-state numbers
to the number of supported sub-states -- discarding
sub-states numbers that were numbered >= the number of states.

But some Bay Trail SOCs use sparse sub-state numbers,
so we can't make such a comparison if we are going
to access those states.

So now we simply check that _some_ sub-states are
supported for the given state, and assume that the
sub-state number in our driver is valid.

In practice, the driver is correct, and even if it were not,
the hardware clips invalid sub-state requests to valid ones.

No entries in the driver require this change,
but Bay Trail will need it.

Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 8e1939f564f4..057ffef37b42 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -584,7 +584,7 @@ static int __init intel_idle_cpuidle_driver_init(void)
         drv->state_count = 1;
 
         for (cstate = 0; cstate < CPUIDLE_STATE_MAX; ++cstate) {
-                int num_substates, mwait_hint, mwait_cstate, mwait_substate;
+                int num_substates, mwait_hint, mwait_cstate;
 
                 if (cpuidle_state_table[cstate].enter == NULL)
                         break;
@@ -597,14 +597,13 @@ static int __init intel_idle_cpuidle_driver_init(void)
 
                 mwait_hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
                 mwait_cstate = MWAIT_HINT2CSTATE(mwait_hint);
-                mwait_substate = MWAIT_HINT2SUBSTATE(mwait_hint);
 
-                /* does the state exist in CPUID.MWAIT? */
+                /* number of sub-states for this state in CPUID.MWAIT */
                 num_substates = (mwait_substates >> ((mwait_cstate + 1) * 4))
                                         & MWAIT_SUBSTATE_MASK;
 
-                /* if sub-state in table is not enumerated by CPUID */
-                if ((mwait_substate + 1) > num_substates)
+                /* if NO sub-states for this state in CPUID, skip it */
+                if (num_substates == 0)
                         continue;
 
                 if (((mwait_cstate + 1) > 2) &&