From: Chen Yu <yu.c.chen@xxxxxxxxx>
commit 4e0ba5577dba686f96c1c10ef4166380667fdec7 upstream.
Currently intel_idle driver gets the c-state information from ACPI
_CST if the processor model is not recognized by it. However the
c-state in _CST starts with index 1 which is different from the
index in intel_idle driver's internal c-state table.
While intel_idle_max_cstate_reached() was previously introduced to
deal with intel_idle driver's internal c-state table, re-using
this function directly on _CST is incorrect.
Fix this by subtracting 1 from the index when checking max_cstate
in the _CST case.
For example, append intel_idle.max_cstate=1 in boot command line,
Before the patch:
grep . /sys/devices/system/cpu/cpu0/cpuidle/state*/name
POLL
After the patch:
grep . /sys/devices/system/cpu/cpu0/cpuidle/state*/name
/sys/devices/system/cpu/cpu0/cpuidle/state0/name:POLL
/sys/devices/system/cpu/cpu0/cpuidle/state1/name:C1_ACPI
Fixes: 18734958e9bf ("intel_idle: Use ACPI _CST for processor models without C-state tables")
Reported-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
Cc: 5.6+ <stable@xxxxxxxxxxxxxxx> # 5.6+
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/idle/intel_idle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1235,7 +1235,7 @@ static void __init intel_idle_init_cstat
struct acpi_processor_cx *cx;
struct cpuidle_state *state;
- if (intel_idle_max_cstate_reached(cstate))
+ if (intel_idle_max_cstate_reached(cstate - 1))
break;
cx = &acpi_state_table.states[cstate];
