hwmon: (pmbus/max31785) Add dual tachometer support

The dual tachometer feature is implemented in hardware with a TACHSEL
input to indicate the rotor under measurement, and exposed on the device
by extending the READ_FAN_SPEED_1 word with two extra bytes*. The need
to read the non-standard four-byte response leads to a cut-down
implementation of i2c_smbus_xfer_emulated() included in the driver.
Further, to expose the second rotor tachometer value to userspace the
values are exposed through virtual pages. We re-route accesses to
FAN_CONFIG_1_2 and READ_FAN_SPEED_1 on pages 23-28 (not defined by the
hardware) to the same registers on pages 0-5, and with the latter command
we extract the value from the second word of the four-byte response.

* The documentation recommends the slower rotor be associated with
TACHSEL=0, which corresponds to the first word of the response. The
TACHSEL=0 measurement is used by the controller's closed-loop fan
management to judge target fan rate.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/Documentation/hwmon/max31785 b/Documentation/hwmon/max31785
index 7b0a0a8cdb6b119d04aa8974622a7ffc5e5f99cf..270c5f865261a030cf026bdde2975f400ce73a65 100644 (file)
--- a/Documentation/hwmon/max31785
+++ b/Documentation/hwmon/max31785
@@ -17,8 +17,9 @@ management with temperature and remote voltage sensing. Various fan control
 features are provided, including PWM frequency control, temperature hysteresis,
 dual tachometer measurements, and fan health monitoring.
 
-For dual rotor fan configuration, the MAX31785 exposes the slowest rotor of the
-two in the fan[1-4]_input attributes.
+For dual-rotor configurations the MAX31785A exposes the second rotor tachometer
+readings in attributes fan[5-8]_input. By contrast the MAX31785 only exposes
+the slowest rotor measurement, and does so in the fan[1-4]_input attributes.
 
 Usage Notes
 -----------
@@ -31,7 +32,8 @@ Sysfs attributes
 
 fan[1-4]_alarm         Fan alarm.
 fan[1-4]_fault         Fan fault.
-fan[1-4]_input         Fan RPM.
+fan[1-8]_input         Fan RPM. On the MAX31785A, inputs 5-8 correspond to the
+                       second rotor of fans 1-4
 fan[1-4]_target                Fan input target
 
 in[1-6]_crit           Critical maximum output voltage

diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c
index 8706a696c89a6c840ebd65d51d33272cf05a2d0c..bffab449be3989821a5bebd0025181a7b9736399 100644 (file)
--- a/drivers/hwmon/pmbus/max31785.c
+++ b/drivers/hwmon/pmbus/max31785.c
@@ -16,9 +16,79 @@
 
 enum max31785_regs {
        MFR_REVISION            = 0x9b,
+       MFR_FAN_CONFIG          = 0xf1,
 };
 
+#define MAX31785                       0x3030
+#define MAX31785A                      0x3040
+
+#define MFR_FAN_CONFIG_DUAL_TACH       BIT(12)
+
 #define MAX31785_NR_PAGES              23
+#define MAX31785_NR_FAN_PAGES          6
+
+static int max31785_read_byte_data(struct i2c_client *client, int page,
+                                  int reg)
+{
+       if (page < MAX31785_NR_PAGES)
+               return -ENODATA;
+
+       switch (reg) {
+       case PMBUS_VOUT_MODE:
+               return -ENOTSUPP;
+       case PMBUS_FAN_CONFIG_12:
+               return pmbus_read_byte_data(client, page - MAX31785_NR_PAGES,
+                                           reg);
+       }
+
+       return -ENODATA;
+}
+
+static int max31785_write_byte(struct i2c_client *client, int page, u8 value)
+{
+       if (page < MAX31785_NR_PAGES)
+               return -ENODATA;
+
+       return -ENOTSUPP;
+}
+
+static int max31785_read_long_data(struct i2c_client *client, int page,
+                                  int reg, u32 *data)
+{
+       unsigned char cmdbuf[1];
+       unsigned char rspbuf[4];
+       int rc;
+
+       struct i2c_msg msg[2] = {
+               {
+                       .addr = client->addr,
+                       .flags = 0,
+                       .len = sizeof(cmdbuf),
+                       .buf = cmdbuf,
+               },
+               {
+                       .addr = client->addr,
+                       .flags = I2C_M_RD,
+                       .len = sizeof(rspbuf),
+                       .buf = rspbuf,
+               },
+       };
+
+       cmdbuf[0] = reg;
+
+       rc = pmbus_set_page(client, page);
+       if (rc < 0)
+               return rc;
+
+       rc = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
+       if (rc < 0)
+               return rc;
+
+       *data = (rspbuf[0] << (0 * 8)) | (rspbuf[1] << (1 * 8)) |
+               (rspbuf[2] << (2 * 8)) | (rspbuf[3] << (3 * 8));
+
+       return rc;
+}
 
 static int max31785_get_pwm(struct i2c_client *client, int page)
 {
@@ -62,9 +132,30 @@ static int max31785_get_pwm_mode(struct i2c_client *client, int page)
 static int max31785_read_word_data(struct i2c_client *client, int page,
                                   int reg)
 {
+       u32 val;
        int rv;
 
        switch (reg) {
+       case PMBUS_READ_FAN_SPEED_1:
+               if (page < MAX31785_NR_PAGES)
+                       return -ENODATA;
+
+               rv = max31785_read_long_data(client, page - MAX31785_NR_PAGES,
+                                            reg, &val);
+               if (rv < 0)
+                       return rv;
+
+               rv = (val >> 16) & 0xffff;
+               break;
+       case PMBUS_FAN_COMMAND_1:
+               /*
+                * PMBUS_FAN_COMMAND_x is probed to judge whether or not to
+                * expose fan control registers.
+                *
+                * Don't expose fan_target attribute for virtual pages.
+                */
+               rv = (page >= MAX31785_NR_PAGES) ? -ENOTSUPP : -ENODATA;
+               break;
        case PMBUS_VIRT_PWM_1:
                rv = max31785_get_pwm(client, page);
                break;
@@ -157,11 +248,15 @@ static int max31785_write_word_data(struct i2c_client *client, int page,
 #define MAX31785_VOUT_FUNCS \
        (PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT)
 
+#define MAX37185_NUM_FAN_PAGES 6
+
 static const struct pmbus_driver_info max31785_info = {
        .pages = MAX31785_NR_PAGES,
 
        .write_word_data = max31785_write_word_data,
+       .read_byte_data = max31785_read_byte_data,
        .read_word_data = max31785_read_word_data,
+       .write_byte = max31785_write_byte,
 
        /* RPM */
        .format[PSC_FAN] = direct,
@@ -208,13 +303,46 @@ static const struct pmbus_driver_info max31785_info = {
        .func[22] = MAX31785_VOUT_FUNCS,
 };
 
+static int max31785_configure_dual_tach(struct i2c_client *client,
+                                       struct pmbus_driver_info *info)
+{
+       int ret;
+       int i;
+
+       for (i = 0; i < MAX31785_NR_FAN_PAGES; i++) {
+               ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
+               if (ret < 0)
+                       return ret;
+
+               ret = i2c_smbus_read_word_data(client, MFR_FAN_CONFIG);
+               if (ret < 0)
+                       return ret;
+
+               if (ret & MFR_FAN_CONFIG_DUAL_TACH) {
+                       int virtual = MAX31785_NR_PAGES + i;
+
+                       info->pages = virtual + 1;
+                       info->func[virtual] |= PMBUS_HAVE_FAN12;
+                       info->func[virtual] |= PMBUS_PAGE_VIRTUAL;
+               }
+       }
+
+       return 0;
+}
+
 static int max31785_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)
 {
        struct device *dev = &client->dev;
        struct pmbus_driver_info *info;
+       bool dual_tach = false;
        s64 ret;
 
+       if (!i2c_check_functionality(client->adapter,
+                                    I2C_FUNC_SMBUS_BYTE_DATA |
+                                    I2C_FUNC_SMBUS_WORD_DATA))
+               return -ENODEV;
+
        info = devm_kzalloc(dev, sizeof(struct pmbus_driver_info), GFP_KERNEL);
        if (!info)
                return -ENOMEM;
@@ -225,6 +353,25 @@ static int max31785_probe(struct i2c_client *client,
        if (ret < 0)
                return ret;
 
+       ret = i2c_smbus_read_word_data(client, MFR_REVISION);
+       if (ret < 0)
+               return ret;
+
+       if (ret == MAX31785A) {
+               dual_tach = true;
+       } else if (ret == MAX31785) {
+               if (!strcmp("max31785a", id->name))
+                       dev_warn(dev, "Expected max3175a, found max31785: cannot provide secondary tachometer readings\n");
+       } else {
+               return -ENODEV;
+       }
+
+       if (dual_tach) {
+               ret = max31785_configure_dual_tach(client, info);
+               if (ret < 0)
+                       return ret;
+       }
+
        return pmbus_do_probe(client, id, info);
 }