net: phy: realtek: add hwmon support for temp sensor on RTL822x

This adds hwmon support for the temperature sensor on RTL822x.
It's available on the standalone versions of the PHY's, and on
the integrated PHY's in RTL8125B/RTL8125D/RTL8126.

Signed-off-by: Heiner Kallweit <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/realtek/Kconfig

···
 	tristate "Realtek PHYs"
 	help
 	  Currently supports RTL821x/RTL822x and fast ethernet PHYs
+
+config REALTEK_PHY_HWMON
+	def_bool REALTEK_PHY && HWMON
+	depends on !(REALTEK_PHY=y && HWMON=m)
+	help
+	  Optional hwmon support for the temperature sensor

drivers/net/phy/realtek/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 realtek-y			+= realtek_main.o
+realtek-$(CONFIG_REALTEK_PHY_HWMON) += realtek_hwmon.o
 obj-$(CONFIG_REALTEK_PHY)	+= realtek.o

drivers/net/phy/realtek/realtek.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef REALTEK_H
+#define REALTEK_H
+
+#include <linux/phy.h>
+
+int rtl822x_hwmon_init(struct phy_device *phydev);
+
+#endif /* REALTEK_H */

drivers/net/phy/realtek/realtek_hwmon.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * HWMON support for Realtek PHY's
+ *
+ * Author: Heiner Kallweit <[e-mail]>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/phy.h>
+
+#include "realtek.h"
+
+#define RTL822X_VND2_TSALRM				0xa662
+#define RTL822X_VND2_TSRR				0xbd84
+#define RTL822X_VND2_TSSR				0xb54c
+
+static int rtl822x_hwmon_get_temp(int raw)
+{
+	if (raw >= 512)
+		raw -= 1024;
+
+	return 1000 * raw / 2;
+}
+
+static int rtl822x_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			      u32 attr, int channel, long *val)
+{
+	struct phy_device *phydev = dev_get_drvdata(dev);
+	int raw;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		raw = phy_read_mmd(phydev, MDIO_MMD_VEND2, RTL822X_VND2_TSRR) & 0x3ff;
+		*val = rtl822x_hwmon_get_temp(raw);
+		break;
+	case hwmon_temp_max:
+		/* Chip reduces speed to 1G if threshold is exceeded */
+		raw = phy_read_mmd(phydev, MDIO_MMD_VEND2, RTL822X_VND2_TSSR) >> 6;
+		*val = rtl822x_hwmon_get_temp(raw);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct hwmon_ops rtl822x_hwmon_ops = {
+	.visible = 0444,
+	.read = rtl822x_hwmon_read,
+};
+
+static const struct hwmon_channel_info * const rtl822x_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_MAX),
+	NULL
+};
+
+static const struct hwmon_chip_info rtl822x_hwmon_chip_info = {
+	.ops = &rtl822x_hwmon_ops,
+	.info = rtl822x_hwmon_info,
+};
+
+int rtl822x_hwmon_init(struct phy_device *phydev)
+{
+	struct device *hwdev, *dev = &phydev->mdio.dev;
+	const char *name;
+
+	/* Ensure over-temp alarm is reset. */
+	phy_clear_bits_mmd(phydev, MDIO_MMD_VEND2, RTL822X_VND2_TSALRM, 3);
+
+	name = devm_hwmon_sanitize_name(dev, dev_name(dev));
+	if (IS_ERR(name))
+		return PTR_ERR(name);
+
+	hwdev = devm_hwmon_device_register_with_info(dev, name, phydev,
+						     &rtl822x_hwmon_chip_info,
+						     NULL);
+	return PTR_ERR_OR_ZERO(hwdev);
+}

drivers/net/phy/realtek/realtek_main.c

···
 #include <linux/delay.h>
 #include <linux/clk.h>
 
+#include "realtek.h"
+
 #define RTL821x_PHYSR				0x11
 #define RTL821x_PHYSR_DUPLEX			BIT(13)
 #define RTL821x_PHYSR_SPEED			GENMASK(15, 14)
···
 	return ret;
 }
 
+static int rtl822x_probe(struct phy_device *phydev)
+{
+	if (IS_ENABLED(CONFIG_REALTEK_PHY_HWMON) &&
+	    phydev->phy_id != RTL_GENERIC_PHYID)
+		return rtl822x_hwmon_init(phydev);
+
+	return 0;
+}
+
 static int rtl822xb_config_init(struct phy_device *phydev)
 {
 	bool has_2500, has_sgmii;
···
 		.match_phy_device = rtl_internal_nbaset_match_phy_device,
 		.name           = "Realtek Internal NBASE-T PHY",
 		.flags		= PHY_IS_INTERNAL,
+		.probe		= rtl822x_probe,
 		.get_features   = rtl822x_get_features,
 		.config_aneg    = rtl822x_config_aneg,
 		.read_status    = rtl822x_read_status,