From mboxrd@z Thu Jan  1 00:00:00 1970
Return-path: <peteasa@gmail.com>
Subject: Re: [PATCH] dell-smm-hwmon: Cache fan_type() calls and use
 fan_status() for fan detection
To: =?UTF-8?Q?Pali_Roh=c3=a1r?= <pali.rohar@gmail.com>,
 Thorsten Leemhuis <fedora@leemhuis.info>
References: <1463842001-17785-1-git-send-email-pali.rohar@gmail.com>
 <201605271245.47383@pali>
 <01084692-618a-31db-76f8-60176d1cd2cc@leemhuis.info>
 <201605271521.10294@pali>
Cc: Jan C Peters <jcpeters89@gmail.com>,
 =?UTF-8?Q?David_Santamar=c3=ada_Rogado?= <howl.nsp@gmail.com>,
 Jean Delvare <jdelvare@suse.com>, Guenter Roeck <linux@roeck-us.net>,
 Tolga Cakir <cevelnet@gmail.com>, linux-hwmon@vger.kernel.org,
 linux-kernel@vger.kernel.org
From: Peter Saunderson <peteasa@gmail.com>
Message-ID: <574B4293.9010404@gmail.com>
Date: Sun, 29 May 2016 20:27:15 +0100
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I have just tested removing i8k_get_fan_type() function from the 
dell-smm-hwmon driver in the kernel on my Dell Inspiron 580 and the fan 
speed problem goes away.  My patch simply replaced fan_type with 
fan_status in i8k_init_hwmon and used the index as the type in 
i8k_hwmon_show_fan_label since index and the type were the same 
numerical value on my machine.

Removing i8k_get_fan_type() function for Dell Inspiron 580 would be a 
very good fix!  Well done for finding it!

On 27/05/16 14:21, Pali Rohár wrote:
> So, once kernel call i8k_get_fan_type() function, then fan speed going
> up/down? Even if it was called only at once? Can you confirm it? Caching
> patch cause that for each fan that function is called exactly one time.
Yes even if the i8k_get_fan_type() function is called once I get the fan 
speed problem.
> If this is problem, we can probably create DMI list of machines which do
> not like i8k_get_fan_type() call and disable it for them.
Please add Dell Inspiron 580 to any blacklist that you create.  The 
DMI_PRODUCT_NAME seems to have a white space at the end:

	{
		/*
		 * CPU fan speed going up and down on Dell Inspiron 580
		 * for unknown reasons.
		 */
		.ident = "Dell Inspiron 580",
		.matches = {
			DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
			DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "Inspiron 580 "),
		},
	},