Date:	Wed, 27 Aug 2014 10:55:18 +0200
From:	Goffredo Baroncelli <kreijack@...ind.it>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Goffredo Baroncelli <kreijack@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jean Delvare <jdelvare@...e.de>,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH][v5] therm_windtunnel does not work properly on PowerMac
 G4

Hi Benjamin,

do you have any feedback about this ? Do you think that it would be possible 
to include these patches in a next pull-for-linus ?

Let me know, if you want other changes.

BR
G.Baroncelli

On 08/09/2014 08:49 AM, Goffredo Baroncelli wrote:
> Hi All,
> 
> 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 5 patches to solve this 
> problem (tested on my PowerMac G4). Only the first two are strictly
> related to the problem, the others three may be skipped.
> 
> 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 a parameter to the therm_windtunnel module 
> to control the kernel log message 
> 
> 4) export the fan speed via sysfs
> 
> 5) export the temperature via the hwmon subsistem
> 
> 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.
> The patch 4) is copyied from the Bryan Christianson's patch (see
> debian bug #741663)
> The patch 5) export the temperatures via hwmon, a more standard 
> interface. I also added the internal sensor of the adm1030, which 
> I called "Case2", because it measure the same temperature /+/- 1C) 
> of the "Case" sensor.
> 
> I have to highlight that I tried to export also the fan speed,
> but I was unable to get it, without affecting the fan speed:
> when I set the bit 2 (TACH 1 En) of the register 0x1 
> (Configuration 2), it seemed that the speed every 4/5s dropped,
> then it raised quickly....
> I didn't perform other test to avoid damages.
> 
> Could you be so kindly to apply these patches ?
> 
> PS:
> I am not LKML subscriber, so please put me in CC in case of reply.
> 
> BR
> G.Baroncelli
> 
> Changelog:
> v1: 2014/07/30
> 	- first issue
> v2: 2014/08/01







> 	- protect with a mutex the check before starting the fan 
> 	  daemon (to protect from parallel drivers instantation)
> 	- reduce the number of module parameters to 1 as suggested by 
>           Jean Delvare
> 	- export the fan speed via sysfs
> v3: 2014/08/06
> 	- export the temperatures via hwmon
> 	- export the internal temperature sensor of the adm1030
> 	- little cleanup due to the suggestion of checkpatch.pl (
> 	  and Jean Delvare)
> 	- removed the "(tune +0)" in the log.
> v4: 2014/08/07
> 	- accepted some small cleanup suggestions from Jean Delvare
> 	- replaced SENSOR_DEVICE_ATTR with DEVICE_ATTR, and
> 	  added ATTRIBUTE_GROUPS() use
> v5: 2014/08/09
> 	- hanlde the return error of 
> 	  hwmon_device_register_with_groups() with IS_ERR() "macro"
> 	- better explanation about the source of patch #4
> 
> [1] I think that the guilty commit is 
> commit 81e5d8646ff6bf323dddcf172aa3cef84468fa12
> Author: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> 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.
> 
>     Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> 
> [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
> 


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