On Sun, Mar 9, 2014 at 8:04 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > On 03/08/2014 10:36 PM, Laszlo Papp wrote: >> >> On Sat, Mar 8, 2014 at 11:50 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >>> >>> On 03/07/2014 10:17 AM, Guenter Roeck wrote: >>>> >>>> >>>> On Fri, Mar 07, 2014 at 03:47:08PM +0000, Laszlo Papp wrote: >>>>> >>>>> >>>>> On Fri, Mar 7, 2014 at 3:37 PM, Jean Delvare <jdelvare@xxxxxxx> wrote: >>>>>>>> >>>>>>>> >>>>>>>> I'm quite confused. While I admit that the term "tachometer speed" >>>>>>>> is >>>>>>>> awkward, the max6650 driver is reporting fan speeds in RPM as every >>>>>>>> other hwmon driver. So I really have no idea what you think is >>>>>>>> wrong. >>>>>>>> What did you think "tachometer speed" was, if not the fan speed? >>>>>>>> Does >>>>>>>> the max6650 driver not return correct fan speeds for you? >>>>> >>>>> >>>>> >>>>> That is some strange behavior. If I do "echo 1 > pwm1_enable; echo 0 > >>>>> pwm1; cat fan1_input", I still see 30 for the connected fan, whereas I >>>>> can see it stopped. Is this an expected behavior? I would expect zero >>>>> as a user. >>>>> >>>> I seem to recall that I had seen that as well, with no fan connected. >>>> Maybe the tachometer registers always read at least '1'. I would think >>>> it is wrong, but we'll have to understand the chip a bit better >>>> to be able to provide a fix. Unless you already have a fix ready, >>>> of course. I'll try to re-test tonight if I find the time. >>>> >>> >>> The reason is (most likely) that your fan input does not have a pull-up >>> resistor. Per datasheet, the fan inputs need a 10kOhm pull-up resistor. >>> I confirmed this with my test board - with the pull-up resistor, >>> inputs read 0, Without pull-up, the reported value is 1, which >>> translates to 30 RPM. >>> >>> You might also need the 10 uF capacitor on the FB pin. >> >> >> Hmm, interesting, but then I wonder how it works fine when getting the >> data from userspace with ioctl (i.e .without the driver) through >> /dev/i2c-1. There must be some trick in that case that I am not yet >> aware of. I will double check the schematics on Monday. >> > > With i2cdump on my system I can see that the tachometer register > holds 0 if the resistor is in place, and the sensors command reports > a fan speed or 0 rpm. If the resistor is not in place, the register > content is 1 and sensors reports 30 rpm. > > sudo i2cdump -y -f 1 0x48 > No size specified (using byte-data access) > 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef > 00: 00 00 0a 0a ff ff 00 00 00 00 00 00 01 01 00 00 ..??........??.. > 10: 01 01 01 01 1f 1f 02 02 91 91 91 91 91 91 91 91 ???????????????? > 20: 00 00 0a 0a ff ff 00 00 00 00 00 00 01 01 00 00 ..??........??.. > > groeck@desktop:~$ sensors max6651-i2c-1-48 > max6651-i2c-1-48 > Adapter: i2c-diolan-u2c at bus 003 device 002 > fan1: 30 RPM (div = 4) > fan2: 0 RPM > fan3: 30 RPM > fan4: 30 RPM > > Only fan2 (TACH1 chip input) has the resistor installed. Hmm, ok. Thank you for the detailed reply! _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
