linux-kernel - Re: [PATCH][drivers/misc/thinkpad_acpi.c] duplicate test if (level & TP_EC_FAN

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Message-ID: <47A81FAE.2090709@tiscali.nl>
Date:	Tue, 05 Feb 2008 09:34:54 +0100
From:	Roel Kluin <12o3l@...cali.nl>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	Roland Dreier <rdreier@...co.com>, len.brown@...el.com,
	ibm-acpi-devel@...ts.sourceforge.net, linux-acpi@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, stable@...nel.org,
	Greg KH <greg@...ah.com>
Subject: Re: [PATCH][drivers/misc/thinkpad_acpi.c] duplicate test if (level
 & TP_EC_FAN_FULLSPEED)

Henrique de Moraes Holschuh wrote:
> On Tue, 05 Feb 2008, Roel Kluin wrote:
>> Roland Dreier wrote:
>>>  >                 /* safety net should the EC not support AUTO
>>>  >                  * or FULLSPEED mode bits and just ignore them */
>>>  >                 if (level & TP_EC_FAN_FULLSPEED)
>>>  >                         level |= 7;     /* safety min speed 7 */
>>>  >                 else if (level & TP_EC_FAN_FULLSPEED)
>>>  >                         level |= 4;     /* safety min speed 4 */
>>>  > 
>>>  > Note the duplicate test 'if (level & TP_EC_FAN_FULLSPEED)'. should
>>>  > this be replaced by
>>>
>>> Actually I suspect one of the two tests should be against TP_EC_FAN_AUTO
>>> (based on the comment).
>> Thanks Roland, for your info
>>
>> based on the comments in commit eaa7571b2d1a08873e4bdd8e6db3431df61cd9ad,
>> I think this should be modified like below:
>>
>> ACPI: thinkpad-acpi: add a safety net for TPEC fan control mode
>> The Linux ThinkPad community is not positive that all ThinkPads that do
>> HFSP EC fan control do implement full-speed and auto modes, some of the
>> earlier ones supporting HFSP might not.
>>
>> If the EC ignores the AUTO or FULL-SPEED bits, it will pay attention to the
>> lower three bits that set the fan level. And as thinkpad-acpi was leaving
>> these set to zero, it would stop(!) the fan, which is Not A Good Thing.
>> So, as a safety net, we now make sure to also set the fan level part of the
>> HFSP register to speed 7 for full-speed, and a minimum of speed 4 for auto
>> mode.
>> --
>> second TP_EC_FAN_FULLSPEED should be P_EC_FAN_AUTO
>>
>>
>> Signed-off-by: Roel Kluin <12o3l@...cali.nl>
>> ---
>> diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
>> index cf56647..3c323fe 100644
>> --- a/drivers/misc/thinkpad_acpi.c
>> +++ b/drivers/misc/thinkpad_acpi.c
>> @@ -4138,7 +4138,7 @@ static int fan_set_level(int level)
>>  		 * or FULLSPEED mode bits and just ignore them */
>>  		if (level & TP_EC_FAN_FULLSPEED)
>>  			level |= 7;	/* safety min speed 7 */
>> -		else if (level & TP_EC_FAN_FULLSPEED)
>> +		else if (level & TP_EC_FAN_AUTO)
>>  			level |= 4;	/* safety min speed 4 */
>>  
>>  		if (!acpi_ec_write(fan_status_offset, level))
> 
> ACK.  This needs to be sent to stable as well.  I think both 2.6.22 and
> 2.6.23 need this patch.
> 

CC stable@...nel.org
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