linux-kernel - Re: [PATCH] dell-smm-hwmon: Cache fan_type() calls and use fan

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Message-Id: <201605271245.47383@pali>
Date:	Fri, 27 May 2016 12:45:47 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Thorsten Leemhuis <fedora@...mhuis.info>
Cc:	Jan C Peters <jcpeters89@...il.com>,
	David Santamaría Rogado <howl.nsp@...il.com>,
	Peter Saunderson <peteasa@...il.com>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Tolga Cakir <cevelnet@...il.com>, linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dell-smm-hwmon: Cache fan_type() calls and use fan_status() for fan detection

On Friday 27 May 2016 12:01:21 Thorsten Leemhuis wrote:
> Pali Rohár wrote on 27.05.2016 11:47:
> > […]
> > I do not see any long taking SMM call here. Are you really sure
> > that your machine freeze when loading or using dell-smm-hwmon?
> 
> Uhh, sorry, it seems something got mixed up somewhere. As mentioned
> earlier in this thread already: The Studio XPS 8000 I have here never
> froze when loading or using dell-smm-hwmon. I only saw its CPU fan
> speed going up and down as described in
> https://bugzilla.kernel.org/show_bug.cgi?id=100121 From the mail that
> started this thread I got the impression that all those problems are
> all related somehow, so I went testing the patch as asked.

Looks like there are two different problems with dell-smm-hwmon driver:

1) Fan speed going randomly up and down without system freeze

2) System freeze at boot time and at that time fan speed goes up

I though that problem with fan speed is SMM freeze, but from your log I 
see that it is not truth. And my patch seems to fix problem 2).

So for problem 1) I need to know:

* Is it regression? I.e. is there kernel version under which i8k (or 
dell-smm-hwmon) is working?

* If it is regression, then I need somebody to fully fully bisect 
problematic commit. And then starts reverting it on top of new kernel 
versions (to check that only that commit cause problem 1)).

-- 
Pali Rohár
pali.rohar@...il.com

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