diff mbox series

[SRU,focal:linux-gcp,14/17] intel_idle: Fix max_cstate for processor models without C-state tables

Message ID 20240911042726.959018-15-marcelo.cerri@canonical.com
State New
Headers show
Series lp:#2080324 - linux-gcp: Improve idle support | expand

Commit Message

Marcelo Henrique Cerri Sept. 11, 2024, 4:27 a.m. UTC 
From: Chen Yu <yu.c.chen@intel.com>

BugLink: https://bugs.launchpad.net/bugs/2080324

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>
(cherry picked from commit 4e0ba5577dba686f96c1c10ef4166380667fdec7)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
---
 drivers/idle/intel_idle.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 9eb131434af3..4abbae526a3f 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1231,7 +1231,7 @@  static void 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];