[PATCH] platform/x86/intel-uncore-freq: Fix current_freq_khz after CPU hotplug

[Guixiong Wei]

When the last CPU of a legacy uncore die goes offline,
uncore_freq_remove_die_entry() clears control_cpu. During CPU hotplug
re-add, uncore_freq_add_entry() still populates sysfs attributes before
assigning the new control CPU. As a result, the current frequency read
returns -ENXIO and current_freq_khz is omitted from the recreated sysfs
group.

Assign control_cpu before the initial read paths and before
create_attr_group() so sysfs recreation uses the new online CPU. If
sysfs creation fails, restore control_cpu to -1 to keep the error path
state consistent.

Fixes: 4d73c6772ab7 ("platform/x86: intel-uncore-freq: Conditionally create attribute for read frequency")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guixiong Wei <weiguixiong@xxxxxxxxxxxxx>
---
 .../x86/intel/uncore-frequency/uncore-frequency-common.c   | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c
index 7070c94324e0..f8137ee92e47 100644
--- a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c
+++ b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-common.c
@@ -275,15 +275,20 @@ int uncore_freq_add_entry(struct uncore_data *data, int cpu)
 			  data->package_id, data->die_id);
 	}
 
+	/*
+	 * Set the control CPU before any read path so entry recreation after CPU
+	 * hotplug can populate read-only attributes from the new online CPU.
+	 */
+	data->control_cpu = cpu;
 	uncore_read(data, &data->initial_min_freq_khz, UNCORE_INDEX_MIN_FREQ);
 	uncore_read(data, &data->initial_max_freq_khz, UNCORE_INDEX_MAX_FREQ);
 
 	ret = create_attr_group(data, data->name);
 	if (ret) {
+		data->control_cpu = -1;
 		if (data->domain_id != UNCORE_DOMAIN_ID_INVALID)
 			ida_free(&intel_uncore_ida, data->instance_id);
 	} else {
-		data->control_cpu = cpu;
 		data->valid = true;
 	}
 
-- 
2.50.1 (Apple Git-155)