linux-kernel - [PATCH] platform/x86/intel-uncore-freq: Check write blocked for ELC

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Message-ID: <20250727210513.2898630-1-srinivas.pandruvada@linux.intel.com>
Date: Sun, 27 Jul 2025 14:05:13 -0700
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: hdegoede@...hat.com,
	ilpo.jarvinen@...ux.intel.com
Cc: platform-driver-x86@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	stable@...r.kernel.org
Subject: [PATCH] platform/x86/intel-uncore-freq: Check write blocked for ELC

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

Fixes: bb516dc79c4a ("platform/x86/intel-uncore-freq: Add support for efficiency latency control")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: stable@...r.kernel.org
---
Non urgent patch. It can go through regular merge window even if it has fix tag.
This is not a current production use case.

Rebased on
https://kernel.googlesource.com/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86
for-next

 .../x86/intel/uncore-frequency/uncore-frequency-tpmi.c       | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-tpmi.c b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-tpmi.c
index 6df55c8e16b7..bfcf92aa4d69 100644
--- a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-tpmi.c
+++ b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-tpmi.c
@@ -192,9 +192,14 @@ 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;
-- 
2.49.0