Register an hwmon device to expose the chip die temperature via the
standard hwmon temperature interface. The temperature sensor is only
available on chip variants that have the ZL3073X_FLAG_DIE_TEMP flag
set and its visibility is controlled via the is_visible callback.

The die temperature register provides a value in 0.1°C units that is
converted to millidegrees Celsius for the hwmon subsystem.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
 drivers/dpll/zl3073x/Makefile |  1 +
 drivers/dpll/zl3073x/core.c   |  7 ++++
 drivers/dpll/zl3073x/hwmon.c  | 67 +++++++++++++++++++++++++++++++++++
 drivers/dpll/zl3073x/hwmon.h  | 16 +++++++++
 4 files changed, 91 insertions(+)
 create mode 100644 drivers/dpll/zl3073x/hwmon.c
 create mode 100644 drivers/dpll/zl3073x/hwmon.h

diff --git a/drivers/dpll/zl3073x/Makefile b/drivers/dpll/zl3073x/Makefile
index 906ec3fbcc202..6930bf7867151 100644
--- a/drivers/dpll/zl3073x/Makefile
+++ b/drivers/dpll/zl3073x/Makefile
@@ -3,6 +3,7 @@
 obj-$(CONFIG_ZL3073X)		+= zl3073x.o
 zl3073x-objs			:= chan.o core.o devlink.o dpll.o	\
 				   flash.o fw.o out.o prop.o ref.o synth.o
+zl3073x-$(CONFIG_HWMON)		+= hwmon.o
 
 obj-$(CONFIG_ZL3073X_I2C)	+= zl3073x_i2c.o
 zl3073x_i2c-objs		:= i2c.o
diff --git a/drivers/dpll/zl3073x/core.c b/drivers/dpll/zl3073x/core.c
index 7eebfc1ad1019..dcea98c31d694 100644
--- a/drivers/dpll/zl3073x/core.c
+++ b/drivers/dpll/zl3073x/core.c
@@ -18,6 +18,7 @@
 #include "core.h"
 #include "devlink.h"
 #include "dpll.h"
+#include "hwmon.h"
 #include "regs.h"
 
 #define ZL_CHIP_INFO(_id, _nchannels, _flags)				\
@@ -1038,6 +1039,12 @@ int zl3073x_dev_probe(struct zl3073x_dev *zldev)
 	if (rc)
 		return rc;
 
+	/* Register hwmon interface */
+	rc = zl3073x_hwmon_init(zldev);
+	if (rc)
+		return dev_err_probe(zldev->dev, rc,
+				     "Failed to register hwmon device\n");
+
 	/* Register the devlink instance and parameters */
 	rc = zl3073x_devlink_register(zldev);
 	if (rc)
diff --git a/drivers/dpll/zl3073x/hwmon.c b/drivers/dpll/zl3073x/hwmon.c
new file mode 100644
index 0000000000000..4b44df4def820
--- /dev/null
+++ b/drivers/dpll/zl3073x/hwmon.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/device.h>
+#include <linux/hwmon.h>
+
+#include "core.h"
+#include "hwmon.h"
+#include "regs.h"
+
+static int zl3073x_hwmon_read(struct device *dev,
+			      enum hwmon_sensor_types type,
+			      u32 attr, int channel, long *val)
+{
+	struct zl3073x_dev *zldev = dev_get_drvdata(dev);
+	u16 raw;
+	int rc;
+
+	if (type != hwmon_temp || attr != hwmon_temp_input)
+		return -EOPNOTSUPP;
+
+	rc = zl3073x_read_u16(zldev, ZL_REG_DIE_TEMP_STATUS, &raw);
+	if (rc)
+		return rc;
+
+	/* Convert from 0.1°C units to millidegrees Celsius */
+	*val = (s16)raw * 100;
+
+	return 0;
+}
+
+static umode_t zl3073x_hwmon_is_visible(const void *data,
+					enum hwmon_sensor_types type,
+					u32 attr, int channel)
+{
+	const struct zl3073x_dev *zldev = data;
+
+	if (type == hwmon_temp && (zldev->info->flags & ZL3073X_FLAG_DIE_TEMP))
+		return 0444;
+
+	return 0;
+}
+
+static const struct hwmon_channel_info * const zl3073x_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	NULL,
+};
+
+static const struct hwmon_ops zl3073x_hwmon_ops = {
+	.is_visible = zl3073x_hwmon_is_visible,
+	.read = zl3073x_hwmon_read,
+};
+
+static const struct hwmon_chip_info zl3073x_hwmon_chip_info = {
+	.ops = &zl3073x_hwmon_ops,
+	.info = zl3073x_hwmon_info,
+};
+
+int zl3073x_hwmon_init(struct zl3073x_dev *zldev)
+{
+	struct device *hwmon;
+
+	hwmon = devm_hwmon_device_register_with_info(zldev->dev, "zl3073x",
+						     zldev,
+						     &zl3073x_hwmon_chip_info,
+						     NULL);
+	return PTR_ERR_OR_ZERO(hwmon);
+}
diff --git a/drivers/dpll/zl3073x/hwmon.h b/drivers/dpll/zl3073x/hwmon.h
new file mode 100644
index 0000000000000..6048d596985ad
--- /dev/null
+++ b/drivers/dpll/zl3073x/hwmon.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _ZL3073X_HWMON_H
+#define _ZL3073X_HWMON_H
+
+#include <linux/kconfig.h>
+
+struct zl3073x_dev;
+
+#if IS_REACHABLE(CONFIG_HWMON)
+int zl3073x_hwmon_init(struct zl3073x_dev *zldev);
+#else
+static inline int zl3073x_hwmon_init(struct zl3073x_dev *zldev) { return 0; }
+#endif
+
+#endif /* _ZL3073X_HWMON_H */
-- 
2.52.0