[PATCH net-next v4] eth: fbnic: Add hardware monitoring support via HWMON interface

[Sanman Pradhan <sanman.p211993@gmail.com>]

From: Sanman Pradhan <sanmanpradhan@meta.com>

This patch adds support for hardware monitoring to the fbnic driver,
allowing for temperature and voltage sensor data to be exposed to
userspace via the HWMON interface. The driver registers a HWMON device
and provides callbacks for reading sensor data, enabling system
admins to monitor the health and operating conditions of fbnic.

Signed-off-by: Sanman Pradhan <sanmanpradhan@meta.com>

---
v4:
  - Fix label name in fbnic_pci.c

v3: https://patchwork.kernel.org/project/netdevbpf/patch/20241004204953.2223536-1-sanman.p211993@gmail.com/

v2: https://patchwork.kernel.org/project/netdevbpf/patch/20241003173618.2479520-1-sanman.p211993@gmail.com/

v1: https://lore.kernel.org/netdev/153c5be4-158e-421a-83a5-5632a9263e87@roeck-us.net/T/

---
 drivers/net/ethernet/meta/fbnic/Makefile      |  1 +
 drivers/net/ethernet/meta/fbnic/fbnic.h       |  4 +
 drivers/net/ethernet/meta/fbnic/fbnic_hwmon.c | 81 +++++++++++++++++++
 drivers/net/ethernet/meta/fbnic/fbnic_mac.h   |  7 ++
 drivers/net/ethernet/meta/fbnic/fbnic_pci.c   |  7 +-
 5 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 drivers/net/ethernet/meta/fbnic/fbnic_hwmon.c

diff --git a/drivers/net/ethernet/meta/fbnic/Makefile b/drivers/net/ethernet/meta/fbnic/Makefile
index ed4533a73c57..41494022792a 100644
--- a/drivers/net/ethernet/meta/fbnic/Makefile
+++ b/drivers/net/ethernet/meta/fbnic/Makefile
@@ -11,6 +11,7 @@ fbnic-y := fbnic_devlink.o \
 	   fbnic_ethtool.o \
 	   fbnic_fw.o \
 	   fbnic_hw_stats.o \
+	   fbnic_hwmon.o \
 	   fbnic_irq.o \
 	   fbnic_mac.o \
 	   fbnic_netdev.o \
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic.h b/drivers/net/ethernet/meta/fbnic/fbnic.h
index 0f9e8d79461c..2d3aa20bc876 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic.h
+++ b/drivers/net/ethernet/meta/fbnic/fbnic.h
@@ -18,6 +18,7 @@
 struct fbnic_dev {
 	struct device *dev;
 	struct net_device *netdev;
+	struct device *hwmon;

 	u32 __iomem *uc_addr0;
 	u32 __iomem *uc_addr4;
@@ -127,6 +128,9 @@ void fbnic_devlink_unregister(struct fbnic_dev *fbd);
 int fbnic_fw_enable_mbx(struct fbnic_dev *fbd);
 void fbnic_fw_disable_mbx(struct fbnic_dev *fbd);

+void fbnic_hwmon_register(struct fbnic_dev *fbd);
+void fbnic_hwmon_unregister(struct fbnic_dev *fbd);
+
 int fbnic_pcs_irq_enable(struct fbnic_dev *fbd);
 void fbnic_pcs_irq_disable(struct fbnic_dev *fbd);

diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_hwmon.c b/drivers/net/ethernet/meta/fbnic/fbnic_hwmon.c
new file mode 100644
index 000000000000..bcd1086e3768
--- /dev/null
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_hwmon.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) Meta Platforms, Inc. and affiliates. */
+
+#include <linux/hwmon.h>
+
+#include "fbnic.h"
+#include "fbnic_mac.h"
+
+static int fbnic_hwmon_sensor_id(enum hwmon_sensor_types type)
+{
+	if (type == hwmon_temp)
+		return FBNIC_SENSOR_TEMP;
+	if (type == hwmon_in)
+		return FBNIC_SENSOR_VOLTAGE;
+
+	return -EOPNOTSUPP;
+}
+
+static umode_t fbnic_hwmon_is_visible(const void *drvdata,
+				      enum hwmon_sensor_types type,
+				      u32 attr, int channel)
+{
+	if (type == hwmon_temp && attr == hwmon_temp_input)
+		return 0444;
+	if (type == hwmon_in && attr == hwmon_in_input)
+		return 0444;
+
+	return 0;
+}
+
+static int fbnic_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			    u32 attr, int channel, long *val)
+{
+	struct fbnic_dev *fbd = dev_get_drvdata(dev);
+	const struct fbnic_mac *mac = fbd->mac;
+	int id;
+
+	id = fbnic_hwmon_sensor_id(type);
+	return id < 0 ? id : mac->get_sensor(fbd, id, val);
+}
+
+static const struct hwmon_ops fbnic_hwmon_ops = {
+	.is_visible = fbnic_hwmon_is_visible,
+	.read = fbnic_hwmon_read,
+};
+
+static const struct hwmon_channel_info *fbnic_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT),
+	NULL
+};
+
+static const struct hwmon_chip_info fbnic_chip_info = {
+	.ops = &fbnic_hwmon_ops,
+	.info = fbnic_hwmon_info,
+};
+
+void fbnic_hwmon_register(struct fbnic_dev *fbd)
+{
+	if (!IS_REACHABLE(CONFIG_HWMON))
+		return;
+
+	fbd->hwmon = hwmon_device_register_with_info(fbd->dev, "fbnic",
+						     fbd, &fbnic_chip_info,
+						     NULL);
+	if (IS_ERR(fbd->hwmon)) {
+		dev_notice(fbd->dev,
+			   "Failed to register hwmon device %pe\n",
+			fbd->hwmon);
+		fbd->hwmon = NULL;
+	}
+}
+
+void fbnic_hwmon_unregister(struct fbnic_dev *fbd)
+{
+	if (!IS_REACHABLE(CONFIG_HWMON) || !fbd->hwmon)
+		return;
+
+	hwmon_device_unregister(fbd->hwmon);
+	fbd->hwmon = NULL;
+}
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_mac.h b/drivers/net/ethernet/meta/fbnic/fbnic_mac.h
index 476239a9d381..05a591653e09 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic_mac.h
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_mac.h
@@ -47,6 +47,11 @@ enum {
 #define FBNIC_LINK_MODE_PAM4	(FBNIC_LINK_50R1)
 #define FBNIC_LINK_MODE_MASK	(FBNIC_LINK_AUTO - 1)

+enum fbnic_sensor_id {
+	FBNIC_SENSOR_TEMP,		/* Temp in millidegrees Centigrade */
+	FBNIC_SENSOR_VOLTAGE,		/* Voltage in millivolts */
+};
+
 /* This structure defines the interface hooks for the MAC. The MAC hooks
  * will be configured as a const struct provided with a set of function
  * pointers.
@@ -83,6 +88,8 @@ struct fbnic_mac {

 	void (*link_down)(struct fbnic_dev *fbd);
 	void (*link_up)(struct fbnic_dev *fbd, bool tx_pause, bool rx_pause);
+
+	int (*get_sensor)(struct fbnic_dev *fbd, int id, long *val);
 };

 int fbnic_mac_init(struct fbnic_dev *fbd);
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_pci.c b/drivers/net/ethernet/meta/fbnic/fbnic_pci.c
index a4809fe0fc24..10b9573d829e 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic_pci.c
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_pci.c
@@ -289,9 +289,11 @@ static int fbnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

 	fbnic_devlink_register(fbd);

+	fbnic_hwmon_register(fbd);
+
 	if (!fbd->dsn) {
 		dev_warn(&pdev->dev, "Reading serial number failed\n");
-		goto init_failure_mode;
+		goto hwmon_unregister;
 	}

 	netdev = fbnic_netdev_alloc(fbd);
@@ -310,6 +312,8 @@ static int fbnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

 ifm_free_netdev:
 	fbnic_netdev_free(fbd);
+hwmon_unregister:
+	fbnic_hwmon_unregister(fbd);
 init_failure_mode:
 	dev_warn(&pdev->dev, "Probe error encountered, entering init failure mode. Normal networking functionality will not be available.\n");
 	 /* Always return 0 even on error so devlink is registered to allow
@@ -345,6 +349,7 @@ static void fbnic_remove(struct pci_dev *pdev)
 		fbnic_netdev_free(fbd);
 	}

+	fbnic_hwmon_unregister(fbd);
 	fbnic_devlink_unregister(fbd);
 	fbnic_fw_disable_mbx(fbd);
 	fbnic_free_irqs(fbd);
--
2.43.5