Re: 2.6.10-mm2: it87 sensor driver stops CPU fan

[Nicolas Pitre <nico@cam.org>]

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On Wed, 19 Jan 2005, Jean Delvare wrote:

> Hi Nicolas,
> 
> > FWIW, I have a Gigabyte motherboard with an it87 chip too.  Reading 
> > about this it87 polarity thing I'm suspecting something is really
> > wrong  here:
> > 
> > When system is idle, the sensors report shows:
> > CPU temp = +25°C and CPU fan = 2136 RPM (and rather noisy)
> > 
> > When system is 100% busy (with dd if=/dev/urandom of=/dev/null):
> > CPU temp = +41°C and CPU fan =   1288 RPM (and obviously much quieter)
> > 
> > I'm running a 2.6.10 kernel (not -mm) so I guess the BIOS settings for
> > fan control are not altered.  And incidentally the BIOS has a setting 
> > called "smart fan control" set to "enabled" which maps to the ITxxF 
> > automatic PWM control mode I suppose.  So if the BIOS actually set the
> > fan polarity wrong then the fan would slow down when the temperature 
> > rises and vice versa, right?
> 
> That's right, what you describe really sounds like a wrong polarity
> setting.
> 
> Could you please tell us what model it is, with what BIOS revision?

>From dmidecode:

        BIOS Information
                Vendor: Award Software International, Inc.
                Version: F5
                Release Date: 11/01/2004

        Base Board Information
                Manufacturer: Gigabyte Technology Co., Ltd.
                Product Name: 8I915GMF
                Version: x.x
                Serial Number:

> I would also appreciate a dump of the chip (isadump 0x295 0x296 unless 
> it lives at some uncommon address) to confirm the guess.

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00: 11 10 80 00 37 ff 00 37 ff 07 13 5b 00 51 40 ff
10: fe fe ff 71 d7 fe 7f fe 00 00 ff ff ff ff ff ff
20: 53 a4 cc b9 b9 89 8b ff c9 c9 fe 19 60 f7 f7 f7
30: ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00
40: 7f 7f 7f 7f 46 7f ff ff 2d ff ff ff ff ff ff ff
50: ff 1c 7f 7f 7f ff 5f 5f 90 5f f9 12 55 00 00 00
60: ff 14 41 23 82 23 ff ff 7f 7f 7f 00 00 7f ff ff
70: ff 14 41 23 82 23 ff ff ff ff ff ff ff ff ff ff
80: 00 00 00 00 ff ff ff ff 40 40 ff ff ff ff ff ff
90: 7f 7f 7f 00 00 7f ff ff 7f 7f 7f 00 00 7f ff ff
a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

> The code Jonas and I have been adding to the it87 driver recently will
> probably not work for you if you leave the "smart fan control" enabled
> in your BIOS setup screen (because we supposed that no reponsible
> motherboard maker would enable this mode without properly configuring
> the polarity beforehand - wrong guess in your case - and are not
> allowing a polarity inversion in this case).

Heh... and it's the default value.

> However, by disabling this
> mode in the BIOS setup screen, you should be able to use the new
> fix_pwm_polarity module register to get the polarity fixed, with manual
> PWM control (no auto mode yet).

I guess the BIOS setting will simply be overwritten so changing the BIOS 
should not affect subsequent use, no?

> You might also search for a BIOS update for your board. I consider the
> behavior your describe a major problem and would expect Gigabyte to fix
> it at some point in time.

Well... I can't find a straight BIOS update for this board.  There is a 
Windows application to fetch and install a new BIOS from the net but 
installing Windows on this machine just for that is not really 
practical.


Nicolas