linux-kernel - [char-misc-next 7/7] mei: csc: wake device while reading firmware status

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Message-ID: <20260201094358.1440593-8-alexander.usyskin@intel.com>
Date: Sun,  1 Feb 2026 11:43:58 +0200
From: Alexander Usyskin <alexander.usyskin@...el.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Menachem Adin <menachem.adin@...el.com>,
	Alexander Usyskin <alexander.usyskin@...el.com>,
	linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [char-misc-next 7/7] mei: csc: wake device while reading firmware status

The CSC has firmware status registers in MMIO and they may be
unaccessible while device is suspended.
Wake device while reading firmware status via sysfs.

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
---
 drivers/misc/mei/main.c    | 18 ++++++++++++++----
 drivers/misc/mei/mei_dev.h |  2 ++
 drivers/misc/mei/pci-csc.c |  2 ++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 6f26d5160788..54f70f513482 100644
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -4,6 +4,7 @@
  * Intel Management Engine Interface (Intel MEI) Linux driver
  */
 
+#include <linux/cleanup.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/kernel.h>
@@ -13,6 +14,7 @@
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/fcntl.h>
+#include <linux/pm_runtime.h>
 #include <linux/poll.h>
 #include <linux/init.h>
 #include <linux/ioctl.h>
@@ -982,14 +984,22 @@ static DEVICE_ATTR_RO(trc);
 static ssize_t fw_status_show(struct device *device,
 		struct device_attribute *attr, char *buf)
 {
-	struct mei_device *dev = dev_get_drvdata(device);
+	struct mei_device *mdev = dev_get_drvdata(device);
 	struct mei_fw_status fw_status;
 	int err, i;
 	ssize_t cnt = 0;
 
-	mutex_lock(&dev->device_lock);
-	err = mei_fw_status(dev, &fw_status);
-	mutex_unlock(&dev->device_lock);
+	if (mdev->read_fws_need_resume) {
+		err = pm_runtime_resume_and_get(mdev->parent);
+		if (err) {
+			dev_err(device, "read fw_status resume error = %d\n", err);
+			return err;
+		}
+	}
+	scoped_guard(mutex, &mdev->device_lock)
+		err = mei_fw_status(mdev, &fw_status);
+	if (mdev->read_fws_need_resume)
+		pm_runtime_put_autosuspend(mdev->parent);
 	if (err) {
 		dev_err(device, "read fw_status error = %d\n", err);
 		return err;
diff --git a/drivers/misc/mei/mei_dev.h b/drivers/misc/mei/mei_dev.h
index 1796c6793a94..d8634a726990 100644
--- a/drivers/misc/mei/mei_dev.h
+++ b/drivers/misc/mei/mei_dev.h
@@ -491,6 +491,7 @@ struct mei_dev_timeouts {
  *
  * @recvd_hw_ready : hw ready message received flag
  * @pg_blocked  : low power mode is not allowed
+ * @read_fws_need_resume: the FW status handler needs HW woken from sleep
  *
  * @wait_hw_ready : wait queue for receive HW ready message form FW
  * @wait_pg     : wait queue for receive PG message from FW
@@ -577,6 +578,7 @@ struct mei_device {
 
 	bool recvd_hw_ready;
 	bool pg_blocked;
+	bool read_fws_need_resume;
 
 	/*
 	 * waiting queue for receive message from FW
diff --git a/drivers/misc/mei/pci-csc.c b/drivers/misc/mei/pci-csc.c
index 15e170b1e0b6..70792bf9b3c0 100644
--- a/drivers/misc/mei/pci-csc.c
+++ b/drivers/misc/mei/pci-csc.c
@@ -67,6 +67,8 @@ static int mei_csc_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (!mdev)
 		return -ENOMEM;
 
+	mdev->read_fws_need_resume = true;
+
 	hw = to_me_hw(mdev);
 
 	/*
-- 
2.43.0