therm_windtunnel doesn't work properly on PowerMac G4

Hi All,

I am writing to you Jean and Benjamin because it seem that both worked on these items.

On a PowerMac G4 I noticed that between the kernel v3.2 and v3.14 I lost the fan management.

I found on internet other references to this kind of problem [2]

**How reproduce:
- booting with the kernel 3.2, the fan is "quite" silent. The module therm_windtunnel is loaded and in the log there are lines like:

	[ 1342.614956] CPU-temp: 58.7 C, Case: 33.7 C,  Fan: 5 (tuned +0)
	[ 1390.637793] CPU-temp: 58.6 C, Case: 33.6 C,  Fan: 5

I had also access to the temperature via the sysfs files:
/sys/devices/temperature/case_temperature /sys/devices/temperature/cpu_temperature

- booting with the kernel 3.14, the fan is very loud. The module therm_windtunnel is not loaded. In the log there aren't any message related to the temperature. The sysfs entries don't exist.

** Analysis
In these Apple machines the module i2c-powermac requires the i2c drivers provided by the module therm_windtunnel.

Between the kernel v3.2 and v3.14 [1] some patches changed the driver name requested by the i2c-powermac module,
so the therm_windtunnel modules is not instantiated anymore.

** Proposed solution
In the following emails I sent you three patches to solve this problem (tested on my PowerMac G4)

1) change the driver name

	therm_ds1775 -> MAC,ds1775
        therm_adm1030 -> MAC,adm1030

so the i2c driver are instantiated by i2c-powermac

2) remove the (unused) method do_attach from the i2c-driver
3) add two parameters to the therm_windtunnel module to control the kernel log message

The patch 1) solve the problem. The patch 2) is a small cleanup. The patch 3) allow a better control of the log in dmesg.

Could you be so kindly to apply these patches ?

BR
G.Baroncelli

[1] I think that the guilty commit is

commit 81e5d8646ff6bf323dddcf172aa3cef84468fa12

Author: Benjamin Herrenschmidt <[email protected]>
Date:   Wed Apr 18 22:16:42 2012 +0000

i2c/powermac: Register i2c devices from device-tree

This causes i2c-powermac to register i2c devices exposed in the device-tree, enabling new-style probing of devices.

Note that we prefix the IDs with "MAC," in order to prevent the generic drivers from matching. This is done on purpose as we only want drivers specifically tested/designed to operate on powermacs to match.

This removes the special case we had for the AMS driver, and updates the driver's match table instead.

[2] There is the debian bug #741663 which highlight the same problem. In the bug discussion there is a patch like the my ones.

See also
https://lists.ozlabs.org/pipermail/linuxppc-dev/2012-July/099561.html

gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5