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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/occ/common.c

···
 		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_lock_interruptible(&occ->lock);
+
+	if (rc)
+		return rc;
+
+	if (active) {
+		if (occ->active) {
+			rc = -EALREADY;
+			goto unlock;
+		}
+
+		occ->error_count = 0;
+		occ->last_safe = 0;
+
+		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;
-
-	/* 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);
-		return rc;
-	}
-
-	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);
-		return rc;
-	}
-
-	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_setup_sysfs(occ);
 	if (rc)
···
 	return rc;
 }
 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 <[e-mail]>");
 MODULE_DESCRIPTION("Common OCC hwmon code");

drivers/hwmon/occ/common.h

···
 	struct attribute_group group;
 	const struct attribute_group *groups[2];
 
+	bool active;
 	int error;                      /* final transfer error after retry */
 	int last_error;			/* latest transfer error */
 	unsigned int error_count;       /* number of xfr errors observed */
···
 	u8 prev_mode;
 };
 
-int occ_setup(struct occ *occ, const char *name);
+int occ_active(struct occ *occ, bool active);
+int occ_setup(struct occ *occ);
 int occ_setup_sysfs(struct occ *occ);
 void occ_shutdown(struct occ *occ);
+void occ_shutdown_sysfs(struct occ *occ);
 void occ_sysfs_poll_done(struct occ *occ);
 int occ_update_response(struct occ *occ);
 

drivers/hwmon/occ/p8_i2c.c

···
 	occ->poll_cmd_data = 0x10;		/* P8 OCC poll data */
 	occ->send_cmd = p8_i2c_occ_send_cmd;
 
-	return occ_setup(occ, "p8_occ");
+	return occ_setup(occ);
 }
 
 static int p8_i2c_occ_remove(struct i2c_client *client)

drivers/hwmon/occ/p9_sbe.c

···
 	occ->poll_cmd_data = 0x20;		/* P9 OCC poll data */
 	occ->send_cmd = p9_sbe_occ_send_cmd;
 
-	rc = occ_setup(occ, "p9_occ");
+	rc = occ_setup(occ);
 	if (rc == -ESHUTDOWN)
 		rc = -ENODEV;	/* Host is shutdown, don't spew errors */
 

drivers/hwmon/occ/sysfs.c

···
 #include <linux/export.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/kernel.h>
+#include <linux/kstrtox.h>
 #include <linux/sysfs.h>
 
 #include "common.h"
 
 /* OCC status register */
 #define OCC_STAT_MASTER			BIT(7)
-#define OCC_STAT_ACTIVE			BIT(0)
 
 /* OCC extended status register */
 #define OCC_EXT_STAT_DVFS_OT		BIT(7)
···
 #define OCC_EXT_STAT_QUICK_DROP		BIT(4)
 #define OCC_EXT_STAT_DVFS_VDD		BIT(3)
 #define OCC_EXT_STAT_GPU_THROTTLE	GENMASK(2, 0)
+
+static ssize_t occ_active_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	int rc;
+	bool active;
+	struct occ *occ = dev_get_drvdata(dev);
+
+	rc = kstrtobool(buf, &active);
+	if (rc)
+		return rc;
+
+	rc = occ_active(occ, active);
+	if (rc)
+		return rc;
+
+	return count;
+}
 
 static ssize_t occ_sysfs_show(struct device *dev,
 			      struct device_attribute *attr, char *buf)
···
 	struct occ_poll_response_header *header;
 	struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
 
-	rc = occ_update_response(occ);
-	if (rc)
-		return rc;
+	if (occ->active) {
+		rc = occ_update_response(occ);
+		if (rc)
+			return rc;
 
-	header = (struct occ_poll_response_header *)occ->resp.data;
+		header = (struct occ_poll_response_header *)occ->resp.data;
 
-	switch (sattr->index) {
-	case 0:
-		val = !!(header->status & OCC_STAT_MASTER);
-		break;
-	case 1:
-		val = !!(header->status & OCC_STAT_ACTIVE);
-		break;
-	case 2:
-		val = !!(header->ext_status & OCC_EXT_STAT_DVFS_OT);
-		break;
-	case 3:
-		val = !!(header->ext_status & OCC_EXT_STAT_DVFS_POWER);
-		break;
-	case 4:
-		val = !!(header->ext_status & OCC_EXT_STAT_MEM_THROTTLE);
-		break;
-	case 5:
-		val = !!(header->ext_status & OCC_EXT_STAT_QUICK_DROP);
-		break;
-	case 6:
-		val = header->occ_state;
-		break;
-	case 7:
-		if (header->status & OCC_STAT_MASTER)
-			val = hweight8(header->occs_present);
-		else
+		switch (sattr->index) {
+		case 0:
+			val = !!(header->status & OCC_STAT_MASTER);
+			break;
+		case 1:
 			val = 1;
-		break;
-	case 8:
-		val = header->ips_status;
-		break;
-	case 9:
-		val = header->mode;
-		break;
-	case 10:
-		val = !!(header->ext_status & OCC_EXT_STAT_DVFS_VDD);
-		break;
-	case 11:
-		val = header->ext_status & OCC_EXT_STAT_GPU_THROTTLE;
-		break;
-	default:
-		return -EINVAL;
+			break;
+		case 2:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_OT);
+			break;
+		case 3:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_POWER);
+			break;
+		case 4:
+			val = !!(header->ext_status &
+				 OCC_EXT_STAT_MEM_THROTTLE);
+			break;
+		case 5:
+			val = !!(header->ext_status & OCC_EXT_STAT_QUICK_DROP);
+			break;
+		case 6:
+			val = header->occ_state;
+			break;
+		case 7:
+			if (header->status & OCC_STAT_MASTER)
+				val = hweight8(header->occs_present);
+			else
+				val = 1;
+			break;
+		case 8:
+			val = header->ips_status;
+			break;
+		case 9:
+			val = header->mode;
+			break;
+		case 10:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_VDD);
+			break;
+		case 11:
+			val = header->ext_status & OCC_EXT_STAT_GPU_THROTTLE;
+			break;
+		default:
+			return -EINVAL;
+		}
+	} else {
+		if (sattr->index == 1)
+			val = 0;
+		else if (sattr->index <= 11)
+			val = -ENODATA;
+		else
+			return -EINVAL;
 	}
 
 	return sysfs_emit(buf, "%d\n", val);
···
 }
 
 static SENSOR_DEVICE_ATTR(occ_master, 0444, occ_sysfs_show, NULL, 0);
-static SENSOR_DEVICE_ATTR(occ_active, 0444, occ_sysfs_show, NULL, 1);
+static SENSOR_DEVICE_ATTR(occ_active, 0644, occ_sysfs_show, occ_active_store,
+			  1);
 static SENSOR_DEVICE_ATTR(occ_dvfs_overtemp, 0444, occ_sysfs_show, NULL, 2);
 static SENSOR_DEVICE_ATTR(occ_dvfs_power, 0444, occ_sysfs_show, NULL, 3);
 static SENSOR_DEVICE_ATTR(occ_mem_throttle, 0444, occ_sysfs_show, NULL, 4);
···
 	 * On the first poll response, we haven't yet created the sysfs
 	 * attributes, so don't make any notify calls.
 	 */
-	if (!occ->hwmon)
+	if (!occ->active)
 		goto done;
 
 	if ((header->status & OCC_STAT_MASTER) !=
 	    (occ->prev_stat & OCC_STAT_MASTER)) {
 		name = sensor_dev_attr_occ_master.dev_attr.attr.name;
-		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
-	}
-
-	if ((header->status & OCC_STAT_ACTIVE) !=
-	    (occ->prev_stat & OCC_STAT_ACTIVE)) {
-		name = sensor_dev_attr_occ_active.dev_attr.attr.name;
 		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
 	}
 
···
 	return sysfs_create_group(&occ->bus_dev->kobj, &occ_sysfs);
 }
 
-void occ_shutdown(struct occ *occ)
+void occ_shutdown_sysfs(struct occ *occ)
 {
 	sysfs_remove_group(&occ->bus_dev->kobj, &occ_sysfs);
 }
-EXPORT_SYMBOL_GPL(occ_shutdown);