]> git.proxmox.com Git - mirror_ubuntu-disco-kernel.git/commitdiff
hwmon: (lm90) Add support for max6695 and max6696
authorGuenter Roeck <guenter.roeck@ericsson.com>
Thu, 28 Oct 2010 18:31:43 +0000 (20:31 +0200)
committerJean Delvare <khali@endymion.delvare>
Thu, 28 Oct 2010 18:31:43 +0000 (20:31 +0200)
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Documentation/hwmon/lm90
drivers/hwmon/Kconfig
drivers/hwmon/lm90.c

index bc2c2b4e0d538fc47e65f8fdceae159fd20614f1..6e963b696d850929f121e510aa02512138a17671 100644 (file)
@@ -84,6 +84,17 @@ Supported chips:
     Addresses scanned: I2C 0x4c
     Datasheet: Publicly available at the Maxim website
                http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
+  * Maxim MAX6695
+    Prefix: 'max6695'
+    Addresses scanned: I2C 0x18
+    Datasheet: Publicly available at the Maxim website
+               http://www.maxim-ic.com/datasheet/index.mvp/id/4199
+  * Maxim MAX6696
+    Prefix: 'max6695'
+    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
+                           0x4c, 0x4d and 0x4e
+    Datasheet: Publicly available at the Maxim website
+               http://www.maxim-ic.com/datasheet/index.mvp/id/4199
   * Winbond/Nuvoton W83L771AWG/ASG
     Prefix: 'w83l771'
     Addresses scanned: I2C 0x4c
@@ -152,6 +163,12 @@ MAX6680 and MAX6681:
   * Selectable address
   * Remote sensor type selection
 
+MAX6695 and MAX6696:
+  * Better local resolution
+  * Selectable address (max6696)
+  * Second critical temperature limit
+  * Two remote sensors
+
 W83L771AWG/ASG
   * The AWG and ASG variants only differ in package format.
   * Filter and alert configuration register at 0xBF
index c357c835eb1e232387f755553c285e911c793a2a..9a3742b67c8ceca37057127e110711b1e3140562 100644 (file)
@@ -614,8 +614,8 @@ config SENSORS_LM90
          If you say yes here you get support for National Semiconductor LM90,
          LM86, LM89 and LM99, Analog Devices ADM1032 and ADT7461, Maxim
          MAX6646, MAX6647, MAX6648, MAX6649, MAX6657, MAX6658, MAX6659,
-         MAX6680, MAX6681 and MAX6692, and Winbond/Nuvoton W83L771AWG/ASG
-         sensor chips.
+         MAX6680, MAX6681, MAX6692, MAX6695, MAX6696, and Winbond/Nuvoton
+         W83L771AWG/ASG sensor chips.
 
          This driver can also be built as a module.  If so, the module
          will be called lm90.
index de544817d673212b04b1a90a9464019bb4f3f9fa..366bb624e655628bd646e44f4d030f7f411016d5 100644 (file)
  * chips. The MAX6680 and MAX6681 only differ in the pinout so they can
  * be treated identically.
  *
+ * This driver also supports the MAX6695 and MAX6696, two other sensor
+ * chips made by Maxim. These are also quite similar to other Maxim
+ * chips, but support three temperature sensors instead of two. MAX6695
+ * and MAX6696 only differ in the pinout so they can be treated identically.
+ *
  * This driver also supports the ADT7461 chip from Analog Devices.
  * It's supported in both compatibility and extended mode. It is mostly
  * compatible with LM90 except for a data format difference for the
@@ -96,7 +101,7 @@ static const unsigned short normal_i2c[] = {
        0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, 0x4c, 0x4d, 0x4e, I2C_CLIENT_END };
 
 enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
-       max6646, w83l771 };
+       max6646, w83l771, max6696 };
 
 /*
  * The LM90 registers
@@ -137,9 +142,10 @@ enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
 #define LM90_REG_R_TCRIT_HYST          0x21
 #define LM90_REG_W_TCRIT_HYST          0x21
 
-/* MAX6646/6647/6649/6657/6658/6659 registers */
+/* MAX6646/6647/6649/6657/6658/6659/6695/6696 registers */
 
 #define MAX6657_REG_R_LOCAL_TEMPL      0x11
+#define MAX6696_REG_R_STATUS2          0x12
 #define MAX6659_REG_R_REMOTE_EMERG     0x16
 #define MAX6659_REG_W_REMOTE_EMERG     0x16
 #define MAX6659_REG_R_LOCAL_EMERG      0x17
@@ -154,6 +160,8 @@ enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
 #define LM90_HAVE_LOCAL_EXT    (1 << 2) /* extended local temperature  */
 #define LM90_HAVE_REM_LIMIT_EXT        (1 << 3) /* extended remote limit       */
 #define LM90_HAVE_EMERGENCY    (1 << 4) /* 3rd upper (emergency) limit */
+#define LM90_HAVE_EMERGENCY_ALARM (1 << 5)/* emergency alarm           */
+#define LM90_HAVE_TEMP3                (1 << 6) /* 3rd temperature sensor      */
 
 /*
  * Functions declaration
@@ -166,6 +174,9 @@ static void lm90_init_client(struct i2c_client *client);
 static void lm90_alert(struct i2c_client *client, unsigned int flag);
 static int lm90_remove(struct i2c_client *client);
 static struct lm90_data *lm90_update_device(struct device *dev);
+static inline void lm90_select_remote_channel(struct i2c_client *client,
+                                             struct lm90_data *data,
+                                             int channel);
 
 /*
  * Driver data (common to all clients)
@@ -186,6 +197,8 @@ static const struct i2c_device_id lm90_id[] = {
        { "max6659", max6659 },
        { "max6680", max6680 },
        { "max6681", max6680 },
+       { "max6695", max6696 },
+       { "max6696", max6696 },
        { "w83l771", w83l771 },
        { }
 };
@@ -217,22 +230,29 @@ struct lm90_data {
        int flags;
 
        u8 config_orig;         /* Original configuration register value */
-       u8 alert_alarms;        /* Which alarm bits trigger ALERT# */
+       u16 alert_alarms;       /* Which alarm bits trigger ALERT# */
+                               /* Upper 8 bits for max6695/96 */
 
        /* registers values */
-       s8 temp8[6];    /* 0: local low limit
+       s8 temp8[8];    /* 0: local low limit
                           1: local high limit
                           2: local critical limit
                           3: remote critical limit
-                          4: local emergency limit (max6659 only)
-                          5: remote emergency limit (max6659 only) */
-       s16 temp11[5];  /* 0: remote input
+                          4: local emergency limit (max6659 and max6695/96)
+                          5: remote emergency limit (max6659 and max6695/96)
+                          6: remote 2 critical limit (max6695/96 only)
+                          7: remote 2 emergency limit (max6695/96 only) */
+       s16 temp11[8];  /* 0: remote input
                           1: remote low limit
                           2: remote high limit
-                          3: remote offset (except max6646 and max6657/58/59)
-                          4: local input */
+                          3: remote offset (except max6646, max6657/58/59,
+                                            and max6695/96)
+                          4: local input
+                          5: remote 2 input (max6695/96 only)
+                          6: remote 2 low limit (max6695/96 only)
+                          7: remote 2 high limit (ma6695/96 only) */
        u8 temp_hyst;
-       u8 alarms; /* bitvector */
+       u16 alarms; /* bitvector (upper 8 bits for max6695/96) */
 };
 
 /*
@@ -390,13 +410,15 @@ static ssize_t show_temp8(struct device *dev, struct device_attribute *devattr,
 static ssize_t set_temp8(struct device *dev, struct device_attribute *devattr,
                         const char *buf, size_t count)
 {
-       static const u8 reg[6] = {
+       static const u8 reg[8] = {
                LM90_REG_W_LOCAL_LOW,
                LM90_REG_W_LOCAL_HIGH,
                LM90_REG_W_LOCAL_CRIT,
                LM90_REG_W_REMOTE_CRIT,
                MAX6659_REG_W_LOCAL_EMERG,
                MAX6659_REG_W_REMOTE_EMERG,
+               LM90_REG_W_REMOTE_CRIT,
+               MAX6659_REG_W_REMOTE_EMERG,
        };
 
        struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
@@ -421,7 +443,11 @@ static ssize_t set_temp8(struct device *dev, struct device_attribute *devattr,
                data->temp8[nr] = temp_to_u8(val);
        else
                data->temp8[nr] = temp_to_s8(val);
+
+       lm90_select_remote_channel(client, data, nr >= 6);
        i2c_smbus_write_byte_data(client, reg[nr], data->temp8[nr]);
+       lm90_select_remote_channel(client, data, 0);
+
        mutex_unlock(&data->update_lock);
        return count;
 }
@@ -453,10 +479,13 @@ static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
        struct {
                u8 high;
                u8 low;
-       } reg[3] = {
-               { LM90_REG_W_REMOTE_LOWH, LM90_REG_W_REMOTE_LOWL },
-               { LM90_REG_W_REMOTE_HIGHH, LM90_REG_W_REMOTE_HIGHL },
-               { LM90_REG_W_REMOTE_OFFSH, LM90_REG_W_REMOTE_OFFSL }
+               int channel;
+       } reg[5] = {
+               { LM90_REG_W_REMOTE_LOWH, LM90_REG_W_REMOTE_LOWL, 0 },
+               { LM90_REG_W_REMOTE_HIGHH, LM90_REG_W_REMOTE_HIGHL, 0 },
+               { LM90_REG_W_REMOTE_OFFSH, LM90_REG_W_REMOTE_OFFSL, 0 },
+               { LM90_REG_W_REMOTE_LOWH, LM90_REG_W_REMOTE_LOWL, 1 },
+               { LM90_REG_W_REMOTE_HIGHH, LM90_REG_W_REMOTE_HIGHL, 1 }
        };
 
        struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(devattr);
@@ -485,11 +514,14 @@ static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
        else
                data->temp11[index] = temp_to_s8(val) << 8;
 
+       lm90_select_remote_channel(client, data, reg[nr].channel);
        i2c_smbus_write_byte_data(client, reg[nr].high,
                                  data->temp11[index] >> 8);
        if (data->flags & LM90_HAVE_REM_LIMIT_EXT)
                i2c_smbus_write_byte_data(client, reg[nr].low,
                                          data->temp11[index] & 0xff);
+       lm90_select_remote_channel(client, data, 0);
+
        mutex_unlock(&data->update_lock);
        return count;
 }
@@ -643,6 +675,62 @@ static const struct attribute_group lm90_emergency_group = {
        .attrs = lm90_emergency_attributes,
 };
 
+static SENSOR_DEVICE_ATTR(temp1_emergency_alarm, S_IRUGO, show_alarm, NULL, 15);
+static SENSOR_DEVICE_ATTR(temp2_emergency_alarm, S_IRUGO, show_alarm, NULL, 13);
+
+static struct attribute *lm90_emergency_alarm_attributes[] = {
+       &sensor_dev_attr_temp1_emergency_alarm.dev_attr.attr,
+       &sensor_dev_attr_temp2_emergency_alarm.dev_attr.attr,
+       NULL
+};
+
+static const struct attribute_group lm90_emergency_alarm_group = {
+       .attrs = lm90_emergency_alarm_attributes,
+};
+
+/*
+ * Additional attributes for devices with 3 temperature sensors
+ */
+static SENSOR_DEVICE_ATTR_2(temp3_input, S_IRUGO, show_temp11, NULL, 0, 5);
+static SENSOR_DEVICE_ATTR_2(temp3_min, S_IWUSR | S_IRUGO, show_temp11,
+       set_temp11, 3, 6);
+static SENSOR_DEVICE_ATTR_2(temp3_max, S_IWUSR | S_IRUGO, show_temp11,
+       set_temp11, 4, 7);
+static SENSOR_DEVICE_ATTR(temp3_crit, S_IWUSR | S_IRUGO, show_temp8,
+       set_temp8, 6);
+static SENSOR_DEVICE_ATTR(temp3_crit_hyst, S_IRUGO, show_temphyst, NULL, 6);
+static SENSOR_DEVICE_ATTR(temp3_emergency, S_IWUSR | S_IRUGO, show_temp8,
+       set_temp8, 7);
+static SENSOR_DEVICE_ATTR(temp3_emergency_hyst, S_IRUGO, show_temphyst,
+                         NULL, 7);
+
+static SENSOR_DEVICE_ATTR(temp3_crit_alarm, S_IRUGO, show_alarm, NULL, 9);
+static SENSOR_DEVICE_ATTR(temp3_fault, S_IRUGO, show_alarm, NULL, 10);
+static SENSOR_DEVICE_ATTR(temp3_min_alarm, S_IRUGO, show_alarm, NULL, 11);
+static SENSOR_DEVICE_ATTR(temp3_max_alarm, S_IRUGO, show_alarm, NULL, 12);
+static SENSOR_DEVICE_ATTR(temp3_emergency_alarm, S_IRUGO, show_alarm, NULL, 14);
+
+static struct attribute *lm90_temp3_attributes[] = {
+       &sensor_dev_attr_temp3_input.dev_attr.attr,
+       &sensor_dev_attr_temp3_min.dev_attr.attr,
+       &sensor_dev_attr_temp3_max.dev_attr.attr,
+       &sensor_dev_attr_temp3_crit.dev_attr.attr,
+       &sensor_dev_attr_temp3_crit_hyst.dev_attr.attr,
+       &sensor_dev_attr_temp3_emergency.dev_attr.attr,
+       &sensor_dev_attr_temp3_emergency_hyst.dev_attr.attr,
+
+       &sensor_dev_attr_temp3_fault.dev_attr.attr,
+       &sensor_dev_attr_temp3_min_alarm.dev_attr.attr,
+       &sensor_dev_attr_temp3_max_alarm.dev_attr.attr,
+       &sensor_dev_attr_temp3_crit_alarm.dev_attr.attr,
+       &sensor_dev_attr_temp3_emergency_alarm.dev_attr.attr,
+       NULL
+};
+
+static const struct attribute_group lm90_temp3_group = {
+       .attrs = lm90_temp3_attributes,
+};
+
 /* pec used for ADM1032 only */
 static ssize_t show_pec(struct device *dev, struct device_attribute *dummy,
                        char *buf)
@@ -720,6 +808,30 @@ static int lm90_read_reg(struct i2c_client *client, u8 reg, u8 *value)
        return 0;
 }
 
+/*
+ * client->update_lock must be held when calling this function (unless we are
+ * in detection or initialization steps), and while a remote channel other
+ * than channel 0 is selected. Also, calling code must make sure to re-select
+ * external channel 0 before releasing the lock. This is necessary because
+ * various registers have different meanings as a result of selecting a
+ * non-default remote channel.
+ */
+static inline void lm90_select_remote_channel(struct i2c_client *client,
+                                             struct lm90_data *data,
+                                             int channel)
+{
+       u8 config;
+
+       if (data->kind == max6696) {
+               lm90_read_reg(client, LM90_REG_R_CONFIG1, &config);
+               config &= ~0x08;
+               if (channel)
+                       config |= 0x08;
+               i2c_smbus_write_byte_data(client, LM90_REG_W_CONFIG1,
+                                         config);
+       }
+}
+
 /* Return 0 if detection is successful, -ENODEV otherwise */
 static int lm90_detect(struct i2c_client *new_client,
                       struct i2c_board_info *info)
@@ -794,6 +906,23 @@ static int lm90_detect(struct i2c_client *new_client,
                }
        } else
        if (man_id == 0x4D) { /* Maxim */
+               int reg_emerg, reg_emerg2, reg_status2;
+
+               /*
+                * We read MAX6659_REG_R_REMOTE_EMERG twice, and re-read
+                * LM90_REG_R_MAN_ID in between. If MAX6659_REG_R_REMOTE_EMERG
+                * exists, both readings will reflect the same value. Otherwise,
+                * the readings will be different.
+                */
+               if ((reg_emerg = i2c_smbus_read_byte_data(new_client,
+                                               MAX6659_REG_R_REMOTE_EMERG)) < 0
+                || i2c_smbus_read_byte_data(new_client, LM90_REG_R_MAN_ID) < 0
+                || (reg_emerg2 = i2c_smbus_read_byte_data(new_client,
+                                               MAX6659_REG_R_REMOTE_EMERG)) < 0
+                || (reg_status2 = i2c_smbus_read_byte_data(new_client,
+                                               MAX6696_REG_R_STATUS2)) < 0)
+                       return -ENODEV;
+
                /*
                 * The MAX6657, MAX6658 and MAX6659 do NOT have a chip_id
                 * register. Reading from that address will return the last
@@ -816,6 +945,24 @@ static int lm90_detect(struct i2c_client *new_client,
                        else
                                name = "max6659";
                } else
+               /*
+                * Even though MAX6695 and MAX6696 do not have a chip ID
+                * register, reading it returns 0x01. Bit 4 of the config1
+                * register is unused and should return zero when read. Bit 0 of
+                * the status2 register is unused and should return zero when
+                * read.
+                *
+                * MAX6695 and MAX6696 have an additional set of temperature
+                * limit registers. We can detect those chips by checking if
+                * one of those registers exists.
+                */
+               if (chip_id == 0x01
+                && (reg_config1 & 0x10) == 0x00
+                && (reg_status2 & 0x01) == 0x00
+                && reg_emerg == reg_emerg2
+                && reg_convrate <= 0x07) {
+                       name = "max6696";
+               } else
                /*
                 * The chip_id register of the MAX6680 and MAX6681 holds the
                 * revision of the chip. The lowest bit of the config1 register
@@ -861,6 +1008,11 @@ static int lm90_detect(struct i2c_client *new_client,
 
 static void lm90_remove_files(struct i2c_client *client, struct lm90_data *data)
 {
+       if (data->flags & LM90_HAVE_TEMP3)
+               sysfs_remove_group(&client->dev.kobj, &lm90_temp3_group);
+       if (data->flags & LM90_HAVE_EMERGENCY_ALARM)
+               sysfs_remove_group(&client->dev.kobj,
+                                  &lm90_emergency_alarm_group);
        if (data->flags & LM90_HAVE_EMERGENCY)
                sysfs_remove_group(&client->dev.kobj,
                                   &lm90_emergency_group);
@@ -901,6 +1053,9 @@ static int lm90_probe(struct i2c_client *new_client,
        case lm86:
                data->alert_alarms = 0x7b;
                break;
+       case max6696:
+               data->alert_alarms = 0x187c;
+               break;
        default:
                data->alert_alarms = 0x7c;
                break;
@@ -908,20 +1063,24 @@ static int lm90_probe(struct i2c_client *new_client,
 
        /* Set chip capabilities */
        if (data->kind != max6657 && data->kind != max6659
-           && data->kind != max6646)
+           && data->kind != max6646 && data->kind != max6696)
                data->flags |= LM90_HAVE_OFFSET;
 
        if (data->kind == max6657 || data->kind == max6659
-           || data->kind == max6646)
+           || data->kind == max6646 || data->kind == max6696)
                data->flags |= LM90_HAVE_LOCAL_EXT;
 
        if (data->kind != max6657 && data->kind != max6659
-           && data->kind != max6646 && data->kind != max6680)
+           && data->kind != max6646 && data->kind != max6680
+           && data->kind != max6696)
                data->flags |= LM90_HAVE_REM_LIMIT_EXT;
 
-       if (data->kind == max6659)
+       if (data->kind == max6659 || data->kind == max6696)
                data->flags |= LM90_HAVE_EMERGENCY;
 
+       if (data->kind == max6696)
+               data->flags |= LM90_HAVE_EMERGENCY_ALARM | LM90_HAVE_TEMP3;
+
        /* Initialize the LM90 chip */
        lm90_init_client(new_client);
 
@@ -946,6 +1105,18 @@ static int lm90_probe(struct i2c_client *new_client,
                if (err)
                        goto exit_remove_files;
        }
+       if (data->flags & LM90_HAVE_EMERGENCY_ALARM) {
+               err = sysfs_create_group(&new_client->dev.kobj,
+                                        &lm90_emergency_alarm_group);
+               if (err)
+                       goto exit_remove_files;
+       }
+       if (data->flags & LM90_HAVE_TEMP3) {
+               err = sysfs_create_group(&new_client->dev.kobj,
+                                        &lm90_temp3_group);
+               if (err)
+                       goto exit_remove_files;
+       }
 
        data->hwmon_dev = hwmon_device_register(&new_client->dev);
        if (IS_ERR(data->hwmon_dev)) {
@@ -993,6 +1164,12 @@ static void lm90_init_client(struct i2c_client *client)
        if (data->kind == max6680)
                config |= 0x18;
 
+       /*
+        * Select external channel 0 for max6695/96
+        */
+       if (data->kind == max6696)
+               config &= ~0x08;
+
        config &= 0xBF; /* run */
        if (config != data->config_orig) /* Only write if changed */
                i2c_smbus_write_byte_data(client, LM90_REG_W_CONFIG1, config);
@@ -1016,10 +1193,14 @@ static int lm90_remove(struct i2c_client *client)
 static void lm90_alert(struct i2c_client *client, unsigned int flag)
 {
        struct lm90_data *data = i2c_get_clientdata(client);
-       u8 config, alarms;
+       u8 config, alarms, alarms2 = 0;
 
        lm90_read_reg(client, LM90_REG_R_STATUS, &alarms);
-       if ((alarms & 0x7f) == 0) {
+
+       if (data->kind == max6696)
+               lm90_read_reg(client, MAX6696_REG_R_STATUS2, &alarms2);
+
+       if ((alarms & 0x7f) == 0 && (alarms2 & 0xfe) == 0) {
                dev_info(&client->dev, "Everything OK\n");
        } else {
                if (alarms & 0x61)
@@ -1032,6 +1213,10 @@ static void lm90_alert(struct i2c_client *client, unsigned int flag)
                        dev_warn(&client->dev,
                                 "temp%d diode open, please check!\n", 2);
 
+               if (alarms2 & 0x18)
+                       dev_warn(&client->dev,
+                                "temp%d out of range, please check!\n", 3);
+
                /* Disable ALERT# output, because these chips don't implement
                  SMBus alert correctly; they should only hold the alert line
                  low briefly. */
@@ -1087,6 +1272,7 @@ static struct lm90_data *lm90_update_device(struct device *dev)
        if (time_after(jiffies, data->last_updated + HZ / 2 + HZ / 10)
         || !data->valid) {
                u8 h, l;
+               u8 alarms;
 
                dev_dbg(&client->dev, "Updating lm90 data.\n");
                lm90_read_reg(client, LM90_REG_R_LOCAL_LOW, &data->temp8[0]);
@@ -1135,7 +1321,27 @@ static struct lm90_data *lm90_update_device(struct device *dev)
                        lm90_read_reg(client, MAX6659_REG_R_REMOTE_EMERG,
                                      &data->temp8[5]);
                }
-               lm90_read_reg(client, LM90_REG_R_STATUS, &data->alarms);
+               lm90_read_reg(client, LM90_REG_R_STATUS, &alarms);
+               data->alarms = alarms;  /* save as 16 bit value */
+
+               if (data->kind == max6696) {
+                       lm90_select_remote_channel(client, data, 1);
+                       lm90_read_reg(client, LM90_REG_R_REMOTE_CRIT,
+                                     &data->temp8[6]);
+                       lm90_read_reg(client, MAX6659_REG_R_REMOTE_EMERG,
+                                     &data->temp8[7]);
+                       lm90_read16(client, LM90_REG_R_REMOTE_TEMPH,
+                                   LM90_REG_R_REMOTE_TEMPL, &data->temp11[5]);
+                       if (!lm90_read_reg(client, LM90_REG_R_REMOTE_LOWH, &h))
+                               data->temp11[6] = h << 8;
+                       if (!lm90_read_reg(client, LM90_REG_R_REMOTE_HIGHH, &h))
+                               data->temp11[7] = h << 8;
+                       lm90_select_remote_channel(client, data, 0);
+
+                       if (!lm90_read_reg(client, MAX6696_REG_R_STATUS2,
+                                          &alarms))
+                               data->alarms |= alarms << 8;
+               }
 
                /* Re-enable ALERT# output if it was originally enabled and
                 * relevant alarms are all clear */