platform/x86/intel-uncore-freq: Check write blocked for ELC

commit dff6f36 upstream.

Add the missing write_blocked check for updating sysfs related to uncore
efficiency latency control (ELC). If write operation is blocked return
error.

Fixes: bb516dc ("platform/x86/intel-uncore-freq: Add support for efficiency latency control")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250727210513.2898630-1-srinivas.pandruvada@linux.intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: spandruvada

drivers/platform/x86/intel/uncore-frequency/uncore-frequency-tpmi.c

@@ -191,9 +191,14 @@ static int uncore_read_control_freq(struct uncore_data *data, unsigned int *valu
 static int write_eff_lat_ctrl(struct uncore_data *data, unsigned int val, enum uncore_index index)
 {
 	struct tpmi_uncore_cluster_info *cluster_info;
+	struct tpmi_uncore_struct *uncore_root;
 	u64 control;
 
 	cluster_info = container_of(data, struct tpmi_uncore_cluster_info, uncore_data);
+	uncore_root = cluster_info->uncore_root;
+
+	if (uncore_root->write_blocked)
+		return -EPERM;
 
 	if (cluster_info->root_domain)
 		return -ENODATA;