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

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Message-ID: <20080206230702.GA12395@kroah.com>
Date:	Wed, 6 Feb 2008 15:07:02 -0800
From:	Greg KH <greg@...ah.com>
To:	Roel Kluin <12o3l@...cali.nl>
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	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
Subject: Re: [PATCH][drivers/misc/thinkpad_acpi.c] duplicate test if (level
	& TP_EC_FAN_FULLSPEED)

On Tue, Feb 05, 2008 at 09:34:54AM +0100, Roel Kluin wrote:
> 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

Please send us a real copy of the patch, when it goes into Linus's tree,
so we know what to apply, and that it is safe to do so.

thanks,

greg k-h
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