hwmon: (occ) Delay hwmon registration until user request

Instead of registering the hwmon device at probe time, use the
existing "occ_active" sysfs file to control when the driver polls
the OCC for sensor data and registers with hwmon. The reason for
this change is that the SBE, which is the device by which the
driver communicates with the OCC, cannot handle communications
during certain system state transitions, resulting in
unrecoverable system errors.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20220427140443.11428-1-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 70 insertions, 30 deletions

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index f00cd59f1d19..d78f4bebc718 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -1149,44 +1149,75 @@ static void occ_parse_poll_response(struct occ *occ)
 		sizeof(*header), size + sizeof(*header));
 }
 
-int occ_setup(struct occ *occ, const char *name)
+int occ_active(struct occ *occ, bool active)
 {
-	int rc;
-
-	mutex_init(&occ->lock);
-	occ->groups[0] = &occ->group;
+	int rc = mutex_lock_interruptible(&occ->lock);
 
-	/* no need to lock */
-	rc = occ_poll(occ);
-	if (rc == -ESHUTDOWN) {
-		dev_info(occ->bus_dev, "host is not ready\n");
-		return rc;
-	} else if (rc < 0) {
-		dev_err(occ->bus_dev,
-			"failed to get OCC poll response=%02x: %d\n",
-			occ->resp.return_status, rc);
+	if (rc)
 		return rc;
-	}
 
-	occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
-	occ_parse_poll_response(occ);
+	if (active) {
+		if (occ->active) {
+			rc = -EALREADY;
+			goto unlock;
+		}
 
-	rc = occ_setup_sensor_attrs(occ);
-	if (rc) {
-		dev_err(occ->bus_dev, "failed to setup sensor attrs: %d\n",
-			rc);
-		return rc;
-	}
+		occ->error_count = 0;
+		occ->last_safe = 0;
 
-	occ->hwmon = devm_hwmon_device_register_with_groups(occ->bus_dev, name,
-							    occ, occ->groups);
-	if (IS_ERR(occ->hwmon)) {
-		rc = PTR_ERR(occ->hwmon);
-		dev_err(occ->bus_dev, "failed to register hwmon device: %d\n",
-			rc);
-		return rc;
+		rc = occ_poll(occ);
+		if (rc < 0) {
+			dev_err(occ->bus_dev,
+				"failed to get OCC poll response=%02x: %d\n",
+				occ->resp.return_status, rc);
+			goto unlock;
+		}
+
+		occ->active = true;
+		occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
+		occ_parse_poll_response(occ);
+
+		rc = occ_setup_sensor_attrs(occ);
+		if (rc) {
+			dev_err(occ->bus_dev,
+				"failed to setup sensor attrs: %d\n", rc);
+			goto unlock;
+		}
+
+		occ->hwmon = hwmon_device_register_with_groups(occ->bus_dev,
+							       "occ", occ,
+							       occ->groups);
+		if (IS_ERR(occ->hwmon)) {
+			rc = PTR_ERR(occ->hwmon);
+			occ->hwmon = NULL;
+			dev_err(occ->bus_dev,
+				"failed to register hwmon device: %d\n", rc);
+			goto unlock;
+		}
+	} else {
+		if (!occ->active) {
+			rc = -EALREADY;
+			goto unlock;
+		}
+
+		if (occ->hwmon)
+			hwmon_device_unregister(occ->hwmon);
+		occ->active = false;
+		occ->hwmon = NULL;
 	}
 
+unlock:
+	mutex_unlock(&occ->lock);
+	return rc;
+}
+
+int occ_setup(struct occ *occ)
+{
+	int rc;
+
+	mutex_init(&occ->lock);
+	occ->groups[0] = &occ->group;
+
 	rc = occ_setup_sysfs(occ);
 	if (rc)
 		dev_err(occ->bus_dev, "failed to setup sysfs: %d\n", rc);
@@ -1195,6 +1226,15 @@ int occ_setup(struct occ *occ, const char *name)
 }
 EXPORT_SYMBOL_GPL(occ_setup);
 
+void occ_shutdown(struct occ *occ)
+{
+	occ_shutdown_sysfs(occ);
+
+	if (occ->hwmon)
+		hwmon_device_unregister(occ->hwmon);
+}
+EXPORT_SYMBOL_GPL(occ_shutdown);
+
 MODULE_AUTHOR("Eddie James <eajames@linux.ibm.com>");
 MODULE_DESCRIPTION("Common OCC hwmon code");
 MODULE_LICENSE("GPL");