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intel_idle: Fix max_cstate for processor models without C-state tables

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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: 18734958e9 ("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>
This commit is contained in:
Chen Yu 2020-10-25 00:29:53 +08:00 committed by Rafael J. Wysocki
parent 3650b228f8
commit 4e0ba5577d
1 changed files with 1 additions and 1 deletions
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2
drivers/idle/intel_idle.c
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@ -1239,7 +1239,7 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
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];