[PATCH 7/7] hwmon: (marvel-env) Notify userspace of environmental events

[Matt Turner <mattst88@gmail.com>]

The firmware reports each change of a sensor's state as a system event
machine check. On one, reread every node from a workqueue and notify
userspace of the alarms that changed. The notifier runs in machine check
context, so it only queues an irq_work, which queues the work.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 Documentation/hwmon/marvel-env.rst |  4 ++
 drivers/hwmon/Kconfig              |  1 +
 drivers/hwmon/marvel-env.c         | 89 ++++++++++++++++++++++++++++++++++++--
 3 files changed, 90 insertions(+), 4 deletions(-)

diff --git a/Documentation/hwmon/marvel-env.rst b/Documentation/hwmon/marvel-env.rst
index db36127c3805..f88feba7bfe4 100644
--- a/Documentation/hwmon/marvel-env.rst
+++ b/Documentation/hwmon/marvel-env.rst
@@ -27,6 +27,10 @@ A refresh keeps the boot CPU in the console with interrupts disabled for up
 to 300 ms per unit, so a unit is refreshed at most once every
 ``update_interval`` milliseconds (10000 by default).
 
+The firmware also reports every change of state as a system event machine
+check. When one arrives, the driver refreshes all units and notifies
+userspace through the alarm attributes.
+
 Sysfs entries
 -------------
 
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 50a1bf966f30..6d17c2e89a7c 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1258,6 +1258,7 @@ config SENSORS_MACSMC_HWMON
 config SENSORS_MARVEL_ENV
 	tristate "Marvel (EV7) AlphaServer environmental sensors"
 	depends on ALPHA_MARVEL || ALPHA_GENERIC
+	select IRQ_WORK
 	help
 	  If you say yes here you get support for the temperature, fan,
 	  voltage and power supply sensors of Marvel AlphaServers (the
diff --git a/drivers/hwmon/marvel-env.c b/drivers/hwmon/marvel-env.c
index cdc7e059e17b..3dd2ea658fa3 100644
--- a/drivers/hwmon/marvel-env.c
+++ b/drivers/hwmon/marvel-env.c
@@ -11,13 +11,16 @@
  */
 
 #include <linux/hwmon.h>
+#include <linux/irq_work.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/notifier.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/workqueue.h>
 
 #include <asm/gct.h>
 #include <asm/marvel_env.h>
@@ -81,17 +84,22 @@ struct marvel_env_node {
 struct marvel_env_chan {
 	struct marvel_env_node *node;
 	unsigned int pkt;		/* packet offset in the node */
+	u8 last_status;
 	char label[32];
 };
 
 struct marvel_env_data {
 	struct device *dev;
+	struct device *hwmon;
 	struct mutex lock;		/* serializes refreshes and reads */
 	unsigned int update_interval;	/* ms */
 	struct marvel_env_node *nodes;
 	unsigned int nr_nodes;
 	struct marvel_env_chan *chans[hwmon_max];
 	unsigned int nr_chans[hwmon_max];
+	struct irq_work irq_work;
+	struct work_struct work;
+	struct notifier_block nb;
 };
 
 static const char * const pe_names[] = {
@@ -226,6 +234,7 @@ static void marvel_env_add_chan(struct marvel_env_data *data,
 	c = &data->chans[type][data->nr_chans[type]++];
 	c->node = n;
 	c->pkt = pkt;
+	c->last_status = env_status(n, pkt + env_status_off(type));
 
 	if (n->cabinet || n->drawer)
 		len = scnprintf(c->label, sizeof(c->label), "Cab%u Dra%u ",
@@ -460,6 +469,72 @@ static const struct {
 	{ hwmon_power, HWMON_P_ALARM | HWMON_P_LABEL },
 };
 
+static const u32 marvel_env_alarm[hwmon_max] = {
+	[hwmon_temp] = hwmon_temp_max_alarm,
+	[hwmon_fan] = hwmon_fan_min_alarm,
+	[hwmon_in] = hwmon_in_alarm,
+	[hwmon_power] = hwmon_power_alarm,
+};
+
+/* Reread everything after a system event and report changed alarms. */
+static void marvel_env_event_work(struct work_struct *work)
+{
+	struct marvel_env_data *data =
+		container_of(work, struct marvel_env_data, work);
+	unsigned int i, k;
+
+	mutex_lock(&data->lock);
+	for (i = 0; i < data->nr_nodes; i++) {
+		data->nodes[i].valid = false;
+		marvel_env_refresh(data, &data->nodes[i]);
+	}
+
+	for (k = 0; k < ARRAY_SIZE(marvel_env_hwmon); k++) {
+		enum hwmon_sensor_types type = marvel_env_hwmon[k].type;
+
+		for (i = 0; i < data->nr_chans[type]; i++) {
+			struct marvel_env_chan *c = &data->chans[type][i];
+			u8 status = env_status(c->node,
+					       c->pkt + env_status_off(type));
+
+			if (status == c->last_status)
+				continue;
+			c->last_status = status;
+			hwmon_notify_event(data->hwmon, type,
+					   marvel_env_alarm[type], i);
+		}
+	}
+	mutex_unlock(&data->lock);
+}
+
+static void marvel_env_irq_work(struct irq_work *irq_work)
+{
+	struct marvel_env_data *data =
+		container_of(irq_work, struct marvel_env_data, irq_work);
+
+	schedule_work(&data->work);
+}
+
+/* Runs in machine check context, so only queue the irq_work. */
+static int marvel_env_event(struct notifier_block *nb, unsigned long action,
+			    void *unused)
+{
+	struct marvel_env_data *data =
+		container_of(nb, struct marvel_env_data, nb);
+
+	irq_work_queue(&data->irq_work);
+	return NOTIFY_OK;
+}
+
+static void marvel_env_unregister(void *arg)
+{
+	struct marvel_env_data *data = arg;
+
+	atomic_notifier_chain_unregister(&marvel_env_notifier, &data->nb);
+	irq_work_sync(&data->irq_work);
+	cancel_work_sync(&data->work);
+}
+
 static const struct hwmon_channel_info * const marvel_env_chip_info =
 	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL);
 
@@ -469,7 +544,6 @@ static int marvel_env_probe(struct platform_device *pdev)
 	const struct hwmon_channel_info **info;
 	struct marvel_env_data *data;
 	struct hwmon_chip_info *chip;
-	struct device *hwmon;
 	unsigned int i, k, nr_info = 0;
 
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
@@ -534,9 +608,16 @@ static int marvel_env_probe(struct platform_device *pdev)
 	chip->ops = &marvel_env_ops;
 	chip->info = info;
 
-	hwmon = devm_hwmon_device_register_with_info(dev, DRVNAME, data, chip,
-						     NULL);
-	return PTR_ERR_OR_ZERO(hwmon);
+	data->hwmon = devm_hwmon_device_register_with_info(dev, DRVNAME, data,
+							   chip, NULL);
+	if (IS_ERR(data->hwmon))
+		return PTR_ERR(data->hwmon);
+
+	init_irq_work(&data->irq_work, marvel_env_irq_work);
+	INIT_WORK(&data->work, marvel_env_event_work);
+	data->nb.notifier_call = marvel_env_event;
+	atomic_notifier_chain_register(&marvel_env_notifier, &data->nb);
+	return devm_add_action_or_reset(dev, marvel_env_unregister, data);
 }
 
 static struct platform_driver marvel_env_driver = {

-- 
2.56.1