| From 4e0ba5577dba686f96c1c10ef4166380667fdec7 Mon Sep 17 00:00:00 2001 |
| From: Chen Yu <yu.c.chen@intel.com> |
| Date: Sun, 25 Oct 2020 00:29:53 +0800 |
| Subject: intel_idle: Fix max_cstate for processor models without C-state tables |
| |
| 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]; |
