net: phy: as21xxx: add hwmon temperature sensor

AS21xxx firmware exposes the on-chip temperature monitor through the
CFG_PARAM/DIRECT IPC command. The monitor needs to be configured and started
before a temperature sample is available. Once started, the GET operation
returns the current temperature as a signed 16.16 Celsius value in response
words 1 and 2.

Add optional hwmon support and expose the temperature as temp1_input in
millidegrees Celsius. If the firmware rejects the temperature monitor setup,
keep probing the PHY and simply skip hwmon registration.

Signed-off-by: Pietro Ameruoso <p.ameruoso@live.it>

Author: pameruoso

drivers/net/phy/Kconfig

@@ -80,6 +80,7 @@ comment "MII PHY device drivers"
 
 config AS21XXX_PHY
 	tristate "Aeonsemi AS21xxx PHYs"
+	depends on HWMON || HWMON=n
 	help
 	  Currently supports the Aeonsemi AS21xxx PHY.
 

drivers/net/phy/as21xxx.c

@@ -7,6 +7,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/firmware.h>
+#include <linux/hwmon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/phy.h>
@@ -113,7 +114,10 @@
 #define IPC_CFG_PARAM_DIRECT_WOL	0x12
 
 /* Sub command of CMD_TEMP_MON */
+#define IPC_CMD_TEMP_MON_START		0x1
+#define IPC_CMD_TEMP_MON_CFG		0x3
 #define IPC_CMD_TEMP_MON_GET		0x4
+#define IPC_CMD_TEMP_MON_CONTINUOUS	0x1
 
 #define AS21XXX_MDIO_AN_C22		0xffe0
 #define AS21XXX_AN_STATES1		0x8005
@@ -603,6 +607,113 @@ static int aeon_dpc_ra_enable(struct phy_device *phydev)
 				 sizeof(data), NULL);
 }
 
+#if IS_ENABLED(CONFIG_HWMON)
+static int aeon_temp_monitor_cmd(struct phy_device *phydev, u16 sub_cmd,
+				 u16 param, u16 *ret_data)
+{
+	u16 data[4];
+
+	data[0] = IPC_CFG_PARAM_DIRECT;
+	data[1] = IPC_CFG_PARAM_DIRECT_TEMP_MON;
+	data[2] = sub_cmd;
+	data[3] = param;
+
+	return aeon_ipc_send_msg(phydev, IPC_CMD_CFG_PARAM, data,
+				 sizeof(data), ret_data);
+}
+
+static int aeon_temp_monitor_enable(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = aeon_temp_monitor_cmd(phydev, IPC_CMD_TEMP_MON_CFG,
+				    IPC_CMD_TEMP_MON_CONTINUOUS, NULL);
+	if (ret < 0)
+		return ret;
+
+	return aeon_temp_monitor_cmd(phydev, IPC_CMD_TEMP_MON_START, 0, NULL);
+}
+
+static int aeon_get_temperature(struct phy_device *phydev, long *temp)
+{
+	u16 ret_data[AEON_IPC_DATA_NUM_REGISTERS] = { 0 };
+	s32 temp_fixed;
+	int ret;
+
+	ret = aeon_temp_monitor_cmd(phydev, IPC_CMD_TEMP_MON_GET, 0, ret_data);
+	if (ret < 0)
+		return ret;
+	if (ret < 3 * sizeof(u16))
+		return -ENODATA;
+
+	temp_fixed = (s32)((u32)ret_data[1] | ((u32)ret_data[2] << 16));
+	*temp = ((s64)temp_fixed * 1000) / 65536;
+
+	return 0;
+}
+
+static int as21xxx_hwmon_read(struct device *dev,
+				      enum hwmon_sensor_types type,
+				      u32 attr, int channel, long *value)
+{
+	struct phy_device *phydev = dev_get_drvdata(dev);
+
+	if (type != hwmon_temp || attr != hwmon_temp_input)
+		return -EOPNOTSUPP;
+
+	return aeon_get_temperature(phydev, value);
+}
+
+static umode_t as21xxx_hwmon_is_visible(const void *data,
+					enum hwmon_sensor_types type,
+					u32 attr, int channel)
+{
+	if (type == hwmon_temp && attr == hwmon_temp_input)
+		return 0444;
+
+	return 0;
+}
+
+static const struct hwmon_channel_info * const as21xxx_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	NULL
+};
+
+static const struct hwmon_ops as21xxx_hwmon_ops = {
+	.is_visible	= as21xxx_hwmon_is_visible,
+	.read		= as21xxx_hwmon_read,
+};
+
+static const struct hwmon_chip_info as21xxx_hwmon_chip_info = {
+	.ops		= &as21xxx_hwmon_ops,
+	.info		= as21xxx_hwmon_info,
+};
+
+static int as21xxx_hwmon_probe(struct phy_device *phydev)
+{
+	struct device *dev = &phydev->mdio.dev;
+	struct device *hwmon_dev;
+	int ret;
+
+	ret = aeon_temp_monitor_enable(phydev);
+	if (ret < 0) {
+		phydev_warn(phydev,
+			    "failed to enable temperature monitor: %d\n", ret);
+		return 0;
+	}
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, NULL, phydev,
+						 &as21xxx_hwmon_chip_info, NULL);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+#else
+static int as21xxx_hwmon_probe(struct phy_device *phydev)
+{
+	return 0;
+}
+#endif
+
 static int as21xxx_probe(struct phy_device *phydev)
 {
 	struct as21xxx_priv *priv;
@@ -657,6 +768,10 @@ static int as21xxx_probe(struct phy_device *phydev)
 	if (ret)
 		return ret;
 
+	ret = as21xxx_hwmon_probe(phydev);
+	if (ret)
+		return ret;
+
 	/* Enable PTP clk if not already Enabled */
 	return phy_set_bits_mmd(phydev, MDIO_MMD_VEND1, VEND1_PTP_CLK,
 				VEND1_PTP_CLK_EN);