There is request to disable specific c-states during bootup for
debug purpose. For example, deeper c-states except C1,C1E,C10
are disabled during bootup otherwise it might not boot up well
due to incorrect setting in FW.
For example, intel_idle.mask_cstate=0x3c, would disable cstate
2,3,4,5 in the table
(1<<2) | (1<<3) | (1<<4) | (1<<5)
which is C6,C7s,C8,C9 on Broxton.
This could have it come up as present, but with c-states disabled,
so user can enable those c-states later to test.
Cc: Len Brown <len.br...@intel.com>
Cc: "Wysocki, Rafael J" <rafael.j.wyso...@intel.com>
Cc: Rui Zhang <rui.zh...@intel.com>
Cc: David Box <david.e....@intel.com>
Cc: "Tan, Raymond" <raymond....@intel.com>
Signed-off-by: Chen Yu <yu.c.c...@intel.com>
---
.../admin-guide/kernel-parameters.txt | 7 ++++
drivers/idle/intel_idle.c | 36 +++++++++++++++++++
2 files changed, 43 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index 7ccd158b3894..93a326c42877 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1733,6 +1733,13 @@
provided by tboot because it makes the system
vulnerable to DMA attacks.
+ intel_idle.mask_cstate= [HW,X86]
+ Mask of C-states to be disabled during bootup. For
+ example, mask_cstate=0x3c, would disable cstate 2,3,4,5
+ in the table
+ (1<<2) | (1<<3) | (1<<4) | (1<<5)
+ which is C6,C7s,C8,C9 on Broxton.
+
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
0 disables intel_idle and fall back on acpi_idle.
1 to 9 specify maximum depth of C-state.
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index fa5ff77b8fe4..ed3233864b69 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -63,6 +63,8 @@ static struct cpuidle_driver intel_idle_driver = {
/* intel_idle.max_cstate=0 disables driver */
static int max_cstate = CPUIDLE_STATE_MAX - 1;
+static unsigned int mask_cstate;
+
static unsigned int mwait_substates;
#define LAPIC_TIMER_ALWAYS_RELIABLE 0xFFFFFFFF
@@ -1354,6 +1356,12 @@ static void __init intel_idle_cpuidle_driver_init(void)
if (num_substates == 0)
continue;
+ if ((1UL<<cstate) & mask_cstate) {
+ pr_info("Disable #%d[%s] by user\n",
+ cstate,
+ cpuidle_state_table[cstate].name);
+ cpuidle_state_table[cstate].disabled = 1;
+ }
/* if state marked as disabled, skip it */
if (cpuidle_state_table[cstate].disabled != 0) {
pr_debug("state %s is disabled\n",
@@ -1480,3 +1488,31 @@ device_initcall(intel_idle_init);
* is the easiest way (currently) to continue doing that.
*/
module_param(max_cstate, int, 0444);
+
+static int mask_cstate_set(const char *arg, const struct kernel_param *kp)
+{
+ int ret = 0;
+ unsigned long new_mask_cstate, max_bit;
+
+ ret = kstrtoul(arg, 0, &new_mask_cstate);
+ if (ret)
+ goto exit_mask;
+
+ max_bit = find_last_bit(&new_mask_cstate, BITS_PER_LONG);
+ if (max_bit >= CPUIDLE_STATE_MAX) {
+ ret = -EINVAL;
+ goto exit_mask;
+ }
+
+ mask_cstate = new_mask_cstate;
+ smp_mb();
+
+exit_mask:
+ return ret;
+}
+
+static const struct kernel_param_ops mask_cstate_ops = {
+ .set = mask_cstate_set,
+ .get = param_get_int,
+};
+module_param_cb(mask_cstate, &mask_cstate_ops, &mask_cstate, 0644);
--
2.17.1
