[Xen-changelog] [xen master] mwait-idle: allow sparse sub-state numbering, for Bay Trail

[patchbot@xxxxxxx]

commit 4d9dfc3803da005b6278df6f5336db4fb95da703
Author:     Len Brown <len.brown@xxxxxxxxx>
AuthorDate: Wed Jul 2 14:49:37 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jul 2 14:49:37 2014 +0200

    mwait-idle: allow sparse sub-state numbering, for Bay Trail
    
    Like acpi_idle, mwait-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@xxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpu/mwait-idle.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index 38172e5..744a3d7 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -555,23 +555,22 @@ static int mwait_idle_cpu_init(struct notifier_block *nfb,
        dev->count = 1;
 
        for (cstate = 0; cpuidle_state_table[cstate].target_residency; 
++cstate) {
-               unsigned int num_substates, hint, state, substate;
+               unsigned int num_substates, hint, state;
                struct acpi_processor_cx *cx;
 
                hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
                state = MWAIT_HINT2CSTATE(hint) + 1;
-               substate = MWAIT_HINT2SUBSTATE(hint);
 
                if (state > max_cstate) {
                        printk(PREFIX "max C-state %u reached\n", max_cstate);
                        break;
                }
 
-               /* Does the state exist in CPUID.MWAIT? */
+               /* Number of sub-states for this state in CPUID.MWAIT. */
                num_substates = (mwait_substates >> (state * 4))
                                & MWAIT_SUBSTATE_MASK;
-               /* if sub-state in table is not enumerated by CPUID */
-               if (substate >= num_substates)
+               /* If NO sub-states for this state in CPUID, skip it. */
+               if (num_substates == 0)
                        continue;
 
                if (dev->count >= ACPI_PROCESSOR_MAX_POWER) {
--
generated by git-patchbot for /home/xen/git/xen.git#master

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