[i2c] SMBus collision on Asus Commando, Intel QX6700

[Jean Delvare]

Hi Trevor,

On Mon, 30 Apr 2007 15:44:48 -0700 (PDT), Trevor Bowen wrote:
> I am trying to debug my first install of lm_sensors on a brand
> new box (Asus Commando, Intel QX6700).  Fortunately, lm_sensors came
> preinstalled with my recent CentOS 5 install.  However, I am getting
> the following error, when I run sensors:
> 
> # sensors
> Can't access procfs/sysfs file
> Unable to find i2c bus information;
> For 2.6 kernels, make sure you have mounted sysfs and libsensors
> was compiled with sysfs support!
> For older kernels, make sure you have done 'modprobe i2c-proc'!

Your OS might be recent, but this looks like an old version of
lm-sensors.

> I have run sensors-detect.  And, I am trying to manually check the
> suggested steps, which when I ran into the above problem.
> 
> I have verified that I have the correct modules inserted and that I
> have sysfs correctly mounted for my kernel version (2.6.18-8.1.1.el5)
> - please see below.

The error message above is admittedly confusing (and was improved by
now.) What it really means it that no hardware monitoring devices were
found. Which means that either the relevant drivers were not loaded, or
they were loaded but do not work as intended.

> Interestingly, dmesg shows several weird errors that I do not understand
> and that look disturbing to me:
> 
> # dmesg
> ... <unrelated lines snipped>
> i2c /dev entries driver
> 
> i801_smbus 0000:00:1f.3: Bus collision! SMBus may be locked until next hard reset. (sorry!)
> 
> ... <duplicate lines snipped>
> i801_smbus 0000:00:1f.3: Bus collision! SMBus may be locked until next hard reset. (sorry!)
> 
> Removing netfilter NETLINK layer.
> 
> i801_smbus 0000:00:1f.3: Bus collision! SMBus may be locked until next hard reset. (sorry!)
> 
> ... <duplicate lines snipped>
> i801_smbus 0000:00:1f.3: Bus collision! SMBus may be locked until next hard reset. (sorry!)

Hmm, that's bad (in case you didn't notice yet.) This suggests that
there is another master on your SMBus, or too much noise on the SMBus
lines.

> I am sure that the hardware is fine, because I monitored everything
> correctly using Asus Probe monitoring tool on Windows XP, just before
> I installed CentOS 5 on the box this morning.

But are you sure that Asus Probe was using the Intel 82801 SMBus to get
the data? It could as well be getting the data from a Super-I/O chip
with embedded hardware monitoring functions, for example.

> Just in case, here's "mount" and "lsmod" results:
> (...)
> # lsmod | grep i2c
> i2c_dev                43849  0
> i2c_isa                39105  1 w83781d
> i2c_ec                 38593  1 sbs
> i2c_i801               41429  0
> i2c_core               56129  6 eeprom,i2c_dev,w83781d,i2c_isa,i2c_ec,i2c_i801

Loading i2c-i801 and i2c-ec at the same time is probably not a good
idea - both drivers could be attempting to grab the same device. I'm
not sure if it could explain the error messages above, though. Is
i2c-ec loaded automatically by your distribution? Does it work? Please
provide the output of "i2cdetect -l".

-- 
Jean Delvare