[char-misc-next v2 7/7] watchdog: mei_wdt: re-register device on event

[Tomas Winkler <tomas.winkler@intel.com>]

From: Alexander Usyskin <alexander.usyskin@intel.com>

For Intel SKL platform the ME device can inform the host via
asynchronous notification that the watchdog feature was activated
on the device. The activation doesn't require reboot.
In that case the driver registers the watchdog device with the kernel.
In the same manner the feature can be deactivated without reboot
in that case the watchdog device should be unregistered.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
V2: rework un/registration in runtime

 drivers/watchdog/mei_wdt.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/drivers/watchdog/mei_wdt.c b/drivers/watchdog/mei_wdt.c
index 00d1b8e630b7..cd79920c473b 100644
--- a/drivers/watchdog/mei_wdt.c
+++ b/drivers/watchdog/mei_wdt.c
@@ -87,6 +87,7 @@ static const char *mei_wdt_state_str(enum mei_wdt_state state)
  * @state: watchdog internal state
  * @resp_required: ping required response
  * @response: ping response
+ * @unregister: unregister worker
  * @timeout: watchdog current timeout
  *
  * @dbgfs_dir: debugfs dir entry
@@ -101,6 +102,7 @@ struct mei_wdt {
 	enum mei_wdt_state state;
 	bool resp_required;
 	struct completion response;
+	struct work_struct unregister;
 	u16 timeout;
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -237,6 +239,13 @@ static void mei_wdt_unregister(struct mei_wdt *wdt)
 	mutex_unlock(&wdt->reg_lock);
 }
 
+static void mei_wdt_unregister_work(struct work_struct *work)
+{
+	struct mei_wdt *wdt = container_of(work, struct mei_wdt, unregister);
+
+	mei_wdt_unregister(wdt);
+}
+
 /**
  * mei_wdt_register - register with the watchdog subsystem
  *
@@ -350,8 +359,13 @@ static void mei_wdt_event_rx(struct mei_cl_device *cldev)
 		return;
 	}
 
-	if (wdt->state == MEI_WDT_RUNNING)
+	if (wdt->state == MEI_WDT_RUNNING) {
+		if (res.wdstate & MEI_WDT_WDSTATE_NOT_REQUIRED) {
+			wdt->state = MEI_WDT_NOT_REQUIRED;
+			schedule_work(&wdt->unregister);
+		}
 		goto out;
+	}
 
 	if (wdt->state == MEI_WDT_PROBE) {
 		if (res.wdstate & MEI_WDT_WDSTATE_NOT_REQUIRED) {
@@ -372,6 +386,21 @@ out:
 		complete(&wdt->response);
 }
 
+/*
+ * mei_wdt_notify_event - callback for event notification
+ *
+ * @cldev: bus device
+ */
+static void mei_wdt_notify_event(struct mei_cl_device *cldev)
+{
+	struct mei_wdt *wdt = mei_cldev_get_drvdata(cldev);
+
+	if (wdt->state != MEI_WDT_NOT_REQUIRED)
+		return;
+	wdt->state = MEI_WDT_IDLE;
+	mei_wdt_register(wdt);
+}
+
 /**
  * mei_wdt_event - callback for event receive
  *
@@ -384,6 +413,9 @@ static void mei_wdt_event(struct mei_cl_device *cldev,
 {
 	if (events & BIT(MEI_CL_EVENT_RX))
 		mei_wdt_event_rx(cldev);
+
+	if (events & BIT(MEI_CL_EVENT_NOTIF))
+		mei_wdt_notify_event(cldev);
 }
 
 /**
@@ -543,6 +575,7 @@ static int mei_wdt_probe(struct mei_cl_device *cldev,
 	wdt->resp_required = mei_cldev_ver(cldev) > 0x1;
 	mutex_init(&wdt->reg_lock);
 	wdt->is_registered = false;
+	INIT_WORK(&wdt->unregister, mei_wdt_unregister_work);
 	init_completion(&wdt->response);
 
 	mei_cldev_set_drvdata(cldev, wdt);
@@ -553,9 +586,13 @@ static int mei_wdt_probe(struct mei_cl_device *cldev,
 		goto err_out;
 	}
 
-	ret = mei_cldev_register_event_cb(wdt->cldev, BIT(MEI_CL_EVENT_RX),
+	ret = mei_cldev_register_event_cb(wdt->cldev,
+					  BIT(MEI_CL_EVENT_RX) |
+					  BIT(MEI_CL_EVENT_NOTIF),
 					  mei_wdt_event, NULL);
-	if (ret) {
+
+	/* on legacy devices notification is not supported */
+	if (ret && ret != -EOPNOTSUPP) {
 		dev_err(&cldev->dev, "Could not register event ret=%d\n", ret);
 		goto err_disable;
 	}
@@ -599,6 +636,8 @@ static int mei_wdt_remove(struct mei_cl_device *cldev)
 	if (!completion_done(&wdt->response))
 		complete(&wdt->response);
 
+	cancel_work_sync(&wdt->unregister);
+
 	mei_wdt_unregister(wdt);
 
 	kref_put(&wdt->refcnt, mei_wdt_release);
-- 
2.4.3