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Subject[PATCH v5 4/4] pmbus (max31785): Add dual tachometer support
Date
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>
---
Documentation/hwmon/max31785 | 8 +-
drivers/hwmon/pmbus/max31785.c | 147 ++++++++++++++++++++++++++++++++++-
2 files changed, 152 insertions(+), 3 deletions(-)

diff --git a/Documentation/hwmon/max31785 b/Documentation/hwmon/max31785
index 7b0a0a8cdb6b..270c5f865261 100644
--- 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 2699134dfbe7..b5389070ae06 100644
--- 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);
}

--
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