regulator: max8973: add support for junction thermal warning

The driver MAX8973 supports the driver for Maxim PMIC MAX77621.
MAX77621 supports the junction temp warning at 120 degC and
140 degC which is configurable. It generates alert signal when
junction temperature crosses these threshold.

MAX77621 does not support the continuous temp monitoring of
junction temperature. It just report whether junction temperature
crossed the threshold or not.

Add support to
- Configure junction temp warning threshold via DT property
to generate alert when it crosses the threshold.
- Add support to interrupt the host from this device when alert
occurred.
- read the junction temp via thermal framework.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

3 files changed, 103 insertions, 0 deletions

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index c77dc08b1202..129359f775d0 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -409,6 +409,7 @@ config REGULATOR_MAX8952
 config REGULATOR_MAX8973
         tristate "Maxim MAX8973 voltage regulator "
         depends on I2C
+        depends on THERMAL && THERMAL_OF
         select REGMAP_I2C
         help
           The MAXIM MAX8973 high-efficiency. three phase, DC-DC step-down
diff --git a/drivers/regulator/max8973-regulator.c b/drivers/regulator/max8973-regulator.c
index 5b75b7c2e3ea..08d2f13eca00 100644
--- a/drivers/regulator/max8973-regulator.c
+++ b/drivers/regulator/max8973-regulator.c
@@ -38,6 +38,9 @@
 #include <linux/i2c.h>
 #include <linux/slab.h>
 #include <linux/regmap.h>
+#include <linux/thermal.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
 
 /* Register definitions */
 #define MAX8973_VOUT                                    0x0
@@ -74,6 +77,7 @@
 #define MAX8973_WDTMR_ENABLE                            BIT(6)
 #define MAX8973_DISCH_ENBABLE                           BIT(5)
 #define MAX8973_FT_ENABLE                               BIT(4)
+#define MAX77621_T_JUNCTION_120                         BIT(7)
 
 #define MAX8973_CKKADV_TRIP_MASK                        0xC
 #define MAX8973_CKKADV_TRIP_DISABLE                     0xC
@@ -93,6 +97,12 @@
 #define MAX8973_VOLATGE_STEP                            6250
 #define MAX8973_BUCK_N_VOLTAGE                          0x80
 
+#define MAX77621_CHIPID_TJINT_S                         BIT(0)
+
+#define MAX77621_NORMAL_OPERATING_TEMP                  100000
+#define MAX77621_TJINT_WARNING_TEMP_120                 120000
+#define MAX77621_TJINT_WARNING_TEMP_140                 140000
+
 enum device_id {
         MAX8973,
         MAX77621
@@ -112,6 +122,9 @@ struct max8973_chip {
         int curr_gpio_val;
         struct regulator_ops ops;
         enum device_id id;
+        int junction_temp_warning;
+        int irq;
+        struct thermal_zone_device *tz_device;
 };
 
 /*
@@ -391,6 +404,10 @@ static int max8973_init_dcdc(struct max8973_chip *max,
         if (pdata->control_flags & MAX8973_CONTROL_FREQ_SHIFT_9PER_ENABLE)
                 control1 |= MAX8973_FREQSHIFT_9PER;
 
+        if ((pdata->junction_temp_warning == MAX77621_TJINT_WARNING_TEMP_120) &&
+            (max->id == MAX77621))
+                control2 |= MAX77621_T_JUNCTION_120;
+
         if (!(pdata->control_flags & MAX8973_CONTROL_PULL_DOWN_ENABLE))
                 control2 |= MAX8973_DISCH_ENBABLE;
 
@@ -457,6 +474,79 @@ static int max8973_init_dcdc(struct max8973_chip *max,
         return ret;
 }
 
+static int max8973_thermal_read_temp(void *data, int *temp)
+{
+        struct max8973_chip *mchip = data;
+        unsigned int val;
+        int ret;
+
+        ret = regmap_read(mchip->regmap, MAX8973_CHIPID1, &val);
+        if (ret < 0) {
+                dev_err(mchip->dev, "Failed to read register CHIPID1, %d", ret);
+                return ret;
+        }
+
+        /* +1 degC to trigger cool devive */
+        if (val & MAX77621_CHIPID_TJINT_S)
+                *temp = mchip->junction_temp_warning + 1000;
+        else
+                *temp = MAX77621_NORMAL_OPERATING_TEMP;
+
+        return 0;
+}
+
+static irqreturn_t max8973_thermal_irq(int irq, void *data)
+{
+        struct max8973_chip *mchip = data;
+
+        thermal_zone_device_update(mchip->tz_device);
+
+        return IRQ_HANDLED;
+}
+
+static const struct thermal_zone_of_device_ops max77621_tz_ops = {
+        .get_temp = max8973_thermal_read_temp,
+};
+
+static int max8973_thermal_init(struct max8973_chip *mchip)
+{
+        struct thermal_zone_device *tzd;
+        struct irq_data *irq_data;
+        unsigned long irq_flags = 0;
+        int ret;
+
+        if (mchip->id != MAX77621)
+                return 0;
+
+        tzd = devm_thermal_zone_of_sensor_register(mchip->dev, 0, mchip,
+                                                   &max77621_tz_ops);
+        if (IS_ERR(tzd)) {
+                ret = PTR_ERR(tzd);
+                dev_err(mchip->dev, "Failed to register thermal sensor: %d\n",
+                        ret);
+                return ret;
+        }
+
+        if (mchip->irq <= 0)
+                return 0;
+
+        irq_data = irq_get_irq_data(mchip->irq);
+        if (irq_data)
+                irq_flags = irqd_get_trigger_type(irq_data);
+
+        ret = devm_request_threaded_irq(mchip->dev, mchip->irq, NULL,
+                                        max8973_thermal_irq,
+                                        IRQF_ONESHOT | IRQF_SHARED | irq_flags,
+                                        dev_name(mchip->dev), mchip);
+        if (ret < 0) {
+                dev_err(mchip->dev, "Failed to request irq %d, %d\n",
+                        mchip->irq, ret);
+                return ret;
+        }
+
+        return 0;
+}
+
 static const struct regmap_config max8973_regmap_config = {
         .reg_bits               = 8,
         .val_bits               = 8,
@@ -521,6 +611,11 @@ static struct max8973_regulator_platform_data *max8973_parse_dt(
                 pdata->control_flags |= MAX8973_CONTROL_CLKADV_TRIP_DISABLED;
         }
 
+        pdata->junction_temp_warning = MAX77621_TJINT_WARNING_TEMP_140;
+        ret = of_property_read_u32(np, "junction-warn-millicelsius", &pval);
+        if (!ret && (pval <= MAX77621_TJINT_WARNING_TEMP_120))
+                pdata->junction_temp_warning = MAX77621_TJINT_WARNING_TEMP_120;
+
         return pdata;
 }
 
@@ -608,6 +703,7 @@ static int max8973_probe(struct i2c_client *client,
         max->enable_external_control = pdata->enable_ext_control;
         max->curr_gpio_val = pdata->dvs_def_state;
         max->curr_vout_reg = MAX8973_VOUT + pdata->dvs_def_state;
+        max->junction_temp_warning = pdata->junction_temp_warning;
 
         if (gpio_is_valid(max->enable_gpio))
                 max->enable_external_control = true;
@@ -718,6 +814,7 @@ static int max8973_probe(struct i2c_client *client,
                 return ret;
         }
 
+        max8973_thermal_init(max);
         return 0;
 }
 
diff --git a/include/linux/regulator/max8973-regulator.h b/include/linux/regulator/max8973-regulator.h
index f6a8a16a0d4d..2fcb9980262a 100644
--- a/include/linux/regulator/max8973-regulator.h
+++ b/include/linux/regulator/max8973-regulator.h
@@ -54,6 +54,10 @@
  * @reg_init_data: The regulator init data.
  * @control_flags: Control flags which are ORed value of above flags to
  *              configure device.
+ * @junction_temp_warning: Junction temp in millicelcius on which warning need
+ *                         to be set. Thermal functionality is only supported on
+ *                         MAX77621. The threshold warning supported by MAX77621
+ *                         are 120C and 140C.
  * @enable_ext_control: Enable the voltage enable/disable through external
  *              control signal from EN input pin. If it is false then
  *              voltage output will be enabled/disabled through EN bit of
@@ -67,6 +71,7 @@
 struct max8973_regulator_platform_data {
         struct regulator_init_data *reg_init_data;
         unsigned long control_flags;
+        unsigned long junction_temp_warning;
         bool enable_ext_control;
         int enable_gpio;
         int dvs_gpio;