[RFC][PATCH] cpufreq: intel_pstate: Delete intel_pstate sysfs if failed to register the driver

[Chen Yu]

There is a corner case that if the intel_pstate driver failed to be
registered(might be due to invalid MSR access) and with the acpi_cpufreq
loaded, the intel_pstate sysfs might still be created, which makes the
user confusing(turbostat for example):

grep . /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
acpi-cpufreq

grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:0
/sys/devices/system/cpu/intel_pstate/min_perf_pct:0
grep: /sys/devices/system/cpu/intel_pstate/no_turbo: Resource temporarily unavailable
grep: /sys/devices/system/cpu/intel_pstate/num_pstates: Resource temporarily unavailable
/sys/devices/system/cpu/intel_pstate/status:off
grep: /sys/devices/system/cpu/intel_pstate/turbo_pct: Resource temporarily unavailable

The existing of intel_pstate sysfs does not mean that the intel_pstate driver
has been successfully loaded(for example, echo off to status), but the
intel_pstate sysfs should not co-exist when acpi-cpufreq is also present.
Fix this issue by deleting the intel_pstate sysfs if the driver failed
to be loaded during bootup.

Reported-by: Wendy Wang <wendy.wang@xxxxxxxxx>
Suggested-by: Zhang Rui <rui.zhang@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 drivers/cpufreq/intel_pstate.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 9a515c460a00..8c5f9680de83 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1420,6 +1420,26 @@ static void __init intel_pstate_sysfs_expose_params(void)
 	}
 }
 
+static void __init intel_pstate_sysfs_clean(void)
+{
+	if (!intel_pstate_kobject)
+		return;
+
+	sysfs_remove_group(intel_pstate_kobject, &intel_pstate_attr_group);
+
+	if (per_cpu_limits)
+		goto release_kobj;
+
+	sysfs_remove_file(intel_pstate_kobject, &max_perf_pct.attr);
+	sysfs_remove_file(intel_pstate_kobject, &min_perf_pct.attr);
+
+	if (x86_match_cpu(intel_pstate_cpu_ee_disable_ids))
+		sysfs_remove_file(intel_pstate_kobject, &energy_efficiency.attr);
+
+release_kobj:
+	kobject_put(intel_pstate_kobject);
+}
+
 static void intel_pstate_sysfs_expose_hwp_dynamic_boost(void)
 {
 	int rc;
@@ -3063,8 +3083,10 @@ static int __init intel_pstate_init(void)
 	mutex_lock(&intel_pstate_driver_lock);
 	rc = intel_pstate_register_driver(default_driver);
 	mutex_unlock(&intel_pstate_driver_lock);
-	if (rc)
+	if (rc) {
+		intel_pstate_sysfs_clean();
 		return rc;
+	}
 
 	if (hwp_active) {
 		const struct x86_cpu_id *id;
-- 
2.17.1