hwmon: (pmbus/isl68137) add support for voltage divider on Vout

Some applications require Vout to be higher than the detectable voltage
range of the Vsense pin for a given rail. In such applications, a voltage
divider may be placed between Vout and the Vsense pin, but this results
in erroneous telemetry being read back from the part. This change adds
support for a voltage divider to be defined in the devicetree for a (or
multiple) specific rail(s) for a supported digital multiphase device and
for the applicable Vout telemetry to be scaled based on the voltage
divider configuration.

This change copies the implementation of the vout-voltage-divider
devicetree property defined in the maxim,max20730 bindings schema since
it is the best fit for the use case of scaling hwmon PMBus telemetry. The
generic voltage-divider property used by many iio drivers was determined
to be a poor fit because that schema is tied directly to iio and the
isl68137 driver is not an iio driver.

Signed-off-by: Grant Peltier <[email protected]>
Message-ID: <8c2d048f87282bcf66313afbf5e923d8fc17b4d7.1731439797[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>

diff --git a/drivers/hwmon/pmbus/isl68137.c b/drivers/hwmon/pmbus/isl68137.c
index 7e53fb1d5ea3036434501cb090434ecc18e4820f..97cc951a13a4948edd1f76b38cc9cfb778eafe84 100644 (file)
--- a/drivers/hwmon/pmbus/isl68137.c
+++ b/drivers/hwmon/pmbus/isl68137.c
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/string.h>
 #include <linux/sysfs.h>
 
@@ -20,6 +21,7 @@
 
 #define ISL68137_VOUT_AVS      0x30
 #define RAA_DMPVR2_READ_VMON   0xc8
+#define MAX_CHANNELS            4
 
 enum chips {
        isl68137,
@@ -72,6 +74,17 @@ enum variants {
        raa_dmpvr2_hv,
 };
 
+struct isl68137_channel {
+       u32 vout_voltage_divider[2];
+};
+
+struct isl68137_data {
+       struct pmbus_driver_info info;
+       struct isl68137_channel channel[MAX_CHANNELS];
+};
+
+#define to_isl68137_data(x)    container_of(x, struct isl68137_data, info)
+
 static const struct i2c_device_id raa_dmpvr_id[];
 
 static ssize_t isl68137_avs_enable_show_page(struct i2c_client *client,
@@ -163,13 +176,32 @@ static const struct attribute_group *isl68137_attribute_groups[] = {
 static int raa_dmpvr2_read_word_data(struct i2c_client *client, int page,
                                     int phase, int reg)
 {
+       const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+       const struct isl68137_data *data = to_isl68137_data(info);
        int ret;
+       u64 temp;
 
        switch (reg) {
        case PMBUS_VIRT_READ_VMON:
                ret = pmbus_read_word_data(client, page, phase,
                                           RAA_DMPVR2_READ_VMON);
                break;
+       case PMBUS_READ_POUT:
+       case PMBUS_READ_VOUT:
+               /*
+                * In cases where a voltage divider is attached to the target
+                * rail between Vout and the Vsense pin, both Vout and Pout
+                * should be scaled by the voltage divider scaling factor.
+                * I.e. Vout = Vsense * Rtotal / Rout
+                */
+               ret = pmbus_read_word_data(client, page, phase, reg);
+               if (ret > 0) {
+                       temp = DIV_U64_ROUND_CLOSEST((u64)ret *
+                               data->channel[page].vout_voltage_divider[1],
+                               data->channel[page].vout_voltage_divider[0]);
+                       ret = clamp_val(temp, 0, 0xffff);
+               }
+               break;
        default:
                ret = -ENODATA;
                break;
@@ -178,6 +210,40 @@ static int raa_dmpvr2_read_word_data(struct i2c_client *client, int page,
        return ret;
 }
 
+static int raa_dmpvr2_write_word_data(struct i2c_client *client, int page,
+                                     int reg, u16 word)
+{
+       const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+       const struct isl68137_data *data = to_isl68137_data(info);
+       int ret;
+       u64 temp;
+
+       switch (reg) {
+       case PMBUS_VOUT_MAX:
+       case PMBUS_VOUT_MARGIN_HIGH:
+       case PMBUS_VOUT_MARGIN_LOW:
+       case PMBUS_VOUT_OV_FAULT_LIMIT:
+       case PMBUS_VOUT_UV_FAULT_LIMIT:
+       case PMBUS_VOUT_COMMAND:
+               /*
+                * In cases where a voltage divider is attached to the target
+                * rail between Vout and the Vsense pin, Vout related PMBus
+                * commands should be scaled based on the expected voltage
+                * at the Vsense pin.
+                * I.e. Vsense = Vout * Rout / Rtotal
+                */
+               temp = DIV_U64_ROUND_CLOSEST((u64)word *
+                               data->channel[page].vout_voltage_divider[0],
+                               data->channel[page].vout_voltage_divider[1]);
+               ret = clamp_val(temp, 0, 0xffff);
+               break;
+       default:
+               ret = -ENODATA;
+               break;
+       }
+       return ret;
+}
+
 static struct pmbus_driver_info raa_dmpvr_info = {
        .pages = 3,
        .format[PSC_VOLTAGE_IN] = direct,
@@ -220,14 +286,90 @@ static struct pmbus_driver_info raa_dmpvr_info = {
            | PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_POUT,
 };
 
+static int isl68137_probe_child_from_dt(struct device *dev,
+                                       struct device_node *child,
+                                       struct isl68137_data *data)
+{
+       u32 channel, rout, rtotal;
+       int err;
+
+       err = of_property_read_u32(child, "reg", &channel);
+       if (err) {
+               dev_err(dev, "missing reg property of %pOFn\n", child);
+               return err;
+       }
+       if (channel >= data->info.pages) {
+               dev_err(dev, "invalid reg %d of %pOFn\n", channel, child);
+               return -EINVAL;
+       }
+
+       err = of_property_read_u32_array(child, "vout-voltage-divider",
+                                        data->channel[channel].vout_voltage_divider,
+                                        ARRAY_SIZE(data->channel[channel].vout_voltage_divider));
+       if (err && err != -EINVAL) {
+               dev_err(dev,
+                       "malformed vout-voltage-divider value for channel %d\n",
+                       channel);
+               return err;
+       }
+
+       rout = data->channel[channel].vout_voltage_divider[0];
+       rtotal = data->channel[channel].vout_voltage_divider[1];
+       if (rout == 0) {
+               dev_err(dev,
+                       "Voltage divider output resistance must be greater than 0\n");
+               return -EINVAL;
+       }
+       if (rtotal < rout) {
+               dev_err(dev,
+                       "Voltage divider total resistance is less than output resistance\n");
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
+static int isl68137_probe_from_dt(struct device *dev,
+                                 struct isl68137_data *data)
+{
+       const struct device_node *np = dev->of_node;
+       struct device_node *child;
+       int err;
+
+       for_each_child_of_node(np, child) {
+               if (strcmp(child->name, "channel"))
+                       continue;
+
+               err = isl68137_probe_child_from_dt(dev, child, data);
+               if (err)
+                       return err;
+       }
+
+       return 0;
+}
+
 static int isl68137_probe(struct i2c_client *client)
 {
+       struct device *dev = &client->dev;
        struct pmbus_driver_info *info;
+       struct isl68137_data *data;
+       int i, err;
 
-       info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
-       if (!info)
+       data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+       if (!data)
                return -ENOMEM;
-       memcpy(info, &raa_dmpvr_info, sizeof(*info));
+
+       /*
+        * Initialize all voltage dividers to Rout=1 and Rtotal=1 to simplify
+        * logic in PMBus word read/write functions
+        */
+       for (i = 0; i < MAX_CHANNELS; i++)
+               memset(data->channel[i].vout_voltage_divider,
+                      1,
+                      sizeof(data->channel[i].vout_voltage_divider));
+
+       memcpy(&data->info, &raa_dmpvr_info, sizeof(data->info));
+       info = &data->info;
 
        switch (i2c_match_id(raa_dmpvr_id, client)->driver_data) {
        case raa_dmpvr1_2rail:
@@ -237,11 +379,14 @@ static int isl68137_probe(struct i2c_client *client)
                info->func[1] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
                    | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT
                    | PMBUS_HAVE_POUT;
+               info->read_word_data = raa_dmpvr2_read_word_data;
+               info->write_word_data = raa_dmpvr2_write_word_data;
                info->groups = isl68137_attribute_groups;
                break;
        case raa_dmpvr2_1rail:
                info->pages = 1;
                info->read_word_data = raa_dmpvr2_read_word_data;
+               info->write_word_data = raa_dmpvr2_write_word_data;
                break;
        case raa_dmpvr2_2rail_nontc:
                info->func[0] &= ~PMBUS_HAVE_TEMP3;
@@ -250,9 +395,11 @@ static int isl68137_probe(struct i2c_client *client)
        case raa_dmpvr2_2rail:
                info->pages = 2;
                info->read_word_data = raa_dmpvr2_read_word_data;
+               info->write_word_data = raa_dmpvr2_write_word_data;
                break;
        case raa_dmpvr2_3rail:
                info->read_word_data = raa_dmpvr2_read_word_data;
+               info->write_word_data = raa_dmpvr2_write_word_data;
                break;
        case raa_dmpvr2_hv:
                info->pages = 1;
@@ -263,11 +410,16 @@ static int isl68137_probe(struct i2c_client *client)
                info->m[PSC_POWER] = 2;
                info->R[PSC_POWER] = -1;
                info->read_word_data = raa_dmpvr2_read_word_data;
+               info->write_word_data = raa_dmpvr2_write_word_data;
                break;
        default:
                return -ENODEV;
        }
 
+       err = isl68137_probe_from_dt(dev, data);
+       if (err)
+               return err;
+
        return pmbus_do_probe(client, info);
 }
 
@@ -318,11 +470,59 @@ static const struct i2c_device_id raa_dmpvr_id[] = {
 
 MODULE_DEVICE_TABLE(i2c, raa_dmpvr_id);
 
+static const struct of_device_id isl68137_of_match[] = {
+       { .compatible = "isil,isl68137", .data = (void *)raa_dmpvr1_2rail },
+       { .compatible = "renesas,isl68220", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl68221", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl68222", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl68223", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl68224", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl68225", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl68226", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl68227", .data = (void *)raa_dmpvr2_1rail },
+       { .compatible = "renesas,isl68229", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl68233", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl68239", .data = (void *)raa_dmpvr2_3rail },
+
+       { .compatible = "renesas,isl69222", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69223", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl69224", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69225", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69227", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl69228", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl69234", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69236", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69239", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl69242", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69243", .data = (void *)raa_dmpvr2_1rail },
+       { .compatible = "renesas,isl69247", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69248", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69254", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69255", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69256", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69259", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "isil,isl69260", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,isl69268", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "isil,isl69269", .data = (void *)raa_dmpvr2_3rail },
+       { .compatible = "renesas,isl69298", .data = (void *)raa_dmpvr2_2rail },
+
+       { .compatible = "renesas,raa228000", .data = (void *)raa_dmpvr2_hv },
+       { .compatible = "renesas,raa228004", .data = (void *)raa_dmpvr2_hv },
+       { .compatible = "renesas,raa228006", .data = (void *)raa_dmpvr2_hv },
+       { .compatible = "renesas,raa228228", .data = (void *)raa_dmpvr2_2rail_nontc },
+       { .compatible = "renesas,raa229001", .data = (void *)raa_dmpvr2_2rail },
+       { .compatible = "renesas,raa229004", .data = (void *)raa_dmpvr2_2rail },
+       { },
+};
+
+MODULE_DEVICE_TABLE(of, isl68137_of_match);
+
 /* This is the driver that will be inserted */
 static struct i2c_driver isl68137_driver = {
        .driver = {
-                  .name = "isl68137",
-                  },
+               .name = "isl68137",
+               .of_match_table = isl68137_of_match,
+       },
        .probe = isl68137_probe,
        .id_table = raa_dmpvr_id,
 };