Re: [v4,6/6] pmbus: max31785: Add dual tachometer support

From: Andrew Jeffery
Date: Thu Nov 09 2017 - 22:12:41 EST

On Sun, 2017-11-05 at 06:58 -0800, Guenter Roeck wrote:
> On Fri, Nov 03, 2017 at 03:53:06PM +1100, Andrew Jeffery wrote:
> > 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 undefined (in hardware) pages
> > 23-28 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 provides the first word of the response. The TACHSEL=0
> > measurement is used by the controller's closed-loop fan management.
> >
> > Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> > ---
> > Documentation/hwmon/max31785 | 8 ++-
> > drivers/hwmon/pmbus/max31785.c | 159 ++++++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 163 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/hwmon/max31785 b/Documentation/hwmon/max31785
> > index e9edbf11948f..8e75efc5e4b9 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 0d97ddf67079..2ca7febb2843 100644
> > --- a/drivers/hwmon/pmbus/max31785.c
> > +++ b/drivers/hwmon/pmbus/max31785.c
> > @@ -16,10 +16,82 @@
> >
> > 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
> >
> > +static int max31785_read_byte_data(struct i2c_client *client, int page,
> > + int reg)
> > +{
> > + switch (reg) {
> > + case PMBUS_VOUT_MODE:
> > + if (page < MAX31785_NR_PAGES)
> > + return -ENODATA;
> > +
> > + return -ENOTSUPP;
> > + case PMBUS_FAN_CONFIG_12:
> > + if (page < MAX31785_NR_PAGES)
> > + return -ENODATA;
> > +
> > + 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)
> > {
> > int config;
> > @@ -76,7 +148,25 @@ static int max31785_read_word_data(struct i2c_client *client, int page,
> > int rv;
> >
> > switch (reg) {
> > + case PMBUS_READ_FAN_SPEED_1:
> > + {
> > + u32 val;
> > +
> > + 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_VIRT_PWM_1:
> > + if (page >= MAX31785_NR_PAGES)
> > + return -ENOTSUPP;
> > +
> > rv = max31785_get_pwm(client, page);
> > if (rv < 0)
> > return rv;
> > @@ -85,10 +175,13 @@ static int max31785_read_word_data(struct i2c_client *client, int page,
> > rv /= 100;
> > break;
> > case PMBUS_VIRT_PWM_ENABLE_1:
> > + if (page >= MAX31785_NR_PAGES)
> > + return -ENOTSUPP;
> > +
> > rv = max31785_get_pwm_mode(client, page);
> > break;
> > default:
> > - rv = -ENODATA;
> > + rv = (page >= MAX31785_NR_PAGES) ? -ENXIO : -ENODATA;
> > break;
> > }
> >
> > @@ -100,6 +193,9 @@ static const int max31785_pwm_modes[] = { 0x7fff, 0x2710, 0xffff };
> > static int max31785_write_word_data(struct i2c_client *client, int page,
> > int reg, u16 word)
> > {
> > + if (page >= MAX31785_NR_PAGES)
> > + return -ENXIO;
> > +
> > switch (reg) {
> > case PMBUS_VIRT_PWM_ENABLE_1:
> > if (word >= ARRAY_SIZE(max31785_pwm_modes))
> > @@ -127,7 +223,9 @@ 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,
> > @@ -174,6 +272,55 @@ static const struct pmbus_driver_info max31785_info = {
> > .func[22] = MAX31785_VOUT_FUNCS,
> > };
> >
> > +static int max31785_configure(struct i2c_client *client,
> > + const struct i2c_device_id *id,
> > + struct pmbus_driver_info *info)
> > +{
> > + struct device *dev = &client->dev;
> > + bool dual_tach = false;
> > + int ret;
> > + int i;
> > +
> > + ret = i2c_smbus_read_word_data(client, MFR_REVISION);
> > + if (ret < 0)
> > + return ret;
> > +
> > + if (!strcmp("max31785a", id->name)) {
> > + if (ret == MAX31785A)
> > + dual_tach = true;
> > + else
> > + dev_warn(dev, "Expected max3175a, found max31785: cannot provide secondary tachometer readings\n");
> > + } else if (!strcmp("max31785", id->name)) {
> > + if (ret == MAX31785A)
> > + dev_info(dev, "Expected max31785, found max3175a: suppressing secondary tachometer attributes\n");
> > + } else {
> > + return -EINVAL;
> > + }
>
> This is too restrictive. I would suggest to move the chip detection part
> to the probe function. Also, since you have it, you should weed out any other
> types (ret could be anything) and not just assume it is MAX31785 if it isn't
> MAX31785A.
>
> The "excpected" messages are ok, but don't unnecessaily suppress attributes.
> If there is a need to do this for some reason, there should be a configuration
> parameter: forcing the user to specify the wrong type on purpose to suppress
> information is just wrong.
>
> dual_tach should not depend on the type in id but on the detected type.

No worries, will fix all of the above.

Thanks for the feedback.

Andrew

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