linux-kernel - Re: [PATCH v4] i8k: Autodetect maximal fan speed and fan RPM multiplier

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Message-Id: <201412221607.34978@pali>
Date:	Mon, 22 Dec 2014 16:07:34 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Valdis.Kletnieks@...edu,
	Steven Honeyman <stevenhoneyman@...il.com>,
	Jean Delvare <jdelvare@...e.de>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Jochen Eisinger <jochen@...guin-breeder.org>
Subject: Re: [PATCH v4] i8k: Autodetect maximal fan speed and fan RPM multiplier

On Sunday 21 December 2014 20:51:14 Guenter Roeck wrote:
> On 12/21/2014 09:23 AM, Pali Rohár wrote:
> > This patch adds new function i8k_get_fan_nominal_speed() for
> > doing SMM call which will return nominal fan RPM for
> > specified fan speed. It returns nominal RPM value at which
> > fan operate when speed (0, 1, 2, 3) is set. It looks like
> > RPM value is not accurate, but still provides very useful
> > information.
> > 
> > First it can be used to validate if certain fan speed could
> > be accepted by SMM for setting fan speed and we can use
> > this routine to detect maximal fan speed.
> > 
> > Second it returns RPM value, so we can check if value looks
> > correct with multiplier 30 or multiplier 1 (until now only
> > these two multiplier were used). If RPM value with
> > multiplier 30 is too high, then multiplier 1 is used.
> > 
> > In case when SMM reports that new function is not supported
> > we will fallback to old hardcoded values. Maximal fan speed
> > would be 2 and RPM multiplier 30.
> > 
> > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> > Tested-by: Pali Rohár <pali.rohar@...il.com>
> 
> Auto-detection of both multiplier and maximum speed tested
> working on M140 (after removing its configuration entry).
> 
> On Studio 1555, multiplier auto-detection works, but fan_max
> auto-detection fails. A speed value of '3' is accepted, but
> it does not set the fan speed to its maximum. Also, after
> setting the speed value to '3', reading it back returns to
> old value. No idea what it does or is expected to do. Reading
> the nominal speed does return a valid value.
> 
> Given that, I think we should not try to auto-detect fan_max,
> but keep the current code (meaning either use 2 or 3
> depending on the configuration data, with 2 as default if
> nothing else is known).
> 
> Thanks,
> Guenter

Ok. In this case I will remove max fan speed detection code and 
we will use config data for those some machines which support 
TURBO speed. If multiplier detection on Studio is working fine, I 
can send another patch which remove config data for Studio 
(because default multiplier is 2).

Can you check which nominal value Studio returns for speed 3? 
Maybe it is some special?

-- 
Pali Rohár
pali.rohar@...il.com

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