intel_idle: re-work bxt_idle_state_table_update() and its helper

Since irtl_ns_units[] has itself zero entries, make sure the caller
recognized those cases along with the MSR read returning zero, as zero
is not a valid value for exit_latency and target_residency.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 14 insertions, 15 deletions

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 170ab8e01075..5300f2545e2a 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1187,6 +1187,9 @@ static unsigned long long irtl_2_usec(unsigned long long irtl)
 {
         unsigned long long ns;
 
+        if (!irtl)
+                return 0;
+
         ns = irtl_ns_units[(irtl >> 10) & 0x3];
 
         return div64_u64((irtl & 0x3FF) * ns, 1000);
@@ -1200,43 +1203,39 @@ static unsigned long long irtl_2_usec(unsigned long long irtl)
 static void bxt_idle_state_table_update(void)
 {
         unsigned long long msr;
+        unsigned int usec;
 
         rdmsrl(MSR_PKGC6_IRTL, msr);
-        if (msr) {
-                unsigned int usec = irtl_2_usec(msr);
-
+        usec = irtl_2_usec(msr);
+        if (usec) {
                 bxt_cstates[2].exit_latency = usec;
                 bxt_cstates[2].target_residency = usec;
         }
 
         rdmsrl(MSR_PKGC7_IRTL, msr);
-        if (msr) {
-                unsigned int usec = irtl_2_usec(msr);
-
+        usec = irtl_2_usec(msr);
+        if (usec) {
                 bxt_cstates[3].exit_latency = usec;
                 bxt_cstates[3].target_residency = usec;
         }
 
         rdmsrl(MSR_PKGC8_IRTL, msr);
-        if (msr) {
-                unsigned int usec = irtl_2_usec(msr);
-
+        usec = irtl_2_usec(msr);
+        if (usec) {
                 bxt_cstates[4].exit_latency = usec;
                 bxt_cstates[4].target_residency = usec;
         }
 
         rdmsrl(MSR_PKGC9_IRTL, msr);
-        if (msr) {
-                unsigned int usec = irtl_2_usec(msr);
-
+        usec = irtl_2_usec(msr);
+        if (usec) {
                 bxt_cstates[5].exit_latency = usec;
                 bxt_cstates[5].target_residency = usec;
         }
 
         rdmsrl(MSR_PKGC10_IRTL, msr);
-        if (msr) {
-                unsigned int usec = irtl_2_usec(msr);
-
+        usec = irtl_2_usec(msr);
+        if (usec) {
                 bxt_cstates[6].exit_latency = usec;
                 bxt_cstates[6].target_residency = usec;
         }