From: Chen Yu yu.c.chen@intel.com
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@intel.com Cc: 5.6+ stable@vger.kernel.org # 5.6+ Signed-off-by: Chen Yu yu.c.chen@intel.com [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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];