From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933429AbcE3P0r (ORCPT ); Mon, 30 May 2016 11:26:47 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35287 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932508AbcE3P0p (ORCPT ); Mon, 30 May 2016 11:26:45 -0400 Subject: Re: [Experimental PATCH] dell-smm-hwmon: Add support for disabling automatic BIOS fan control To: =?UTF-8?Q?Pali_Roh=c3=a1r?= References: <1463917836-12985-1-git-send-email-pali.rohar@gmail.com> <830c86c9-af25-b31a-0526-4c1bc0232c53@gmail.com> <20160530093204.GR29844@pali> Cc: Jean Delvare , Guenter Roeck , =?UTF-8?B?TWljaGHFgiBLxJlwaWXFhA==?= , Andy Lutomirski , Jethro , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org From: Gabriele Mazzotta Message-ID: Date: Mon, 30 May 2016 17:26:36 +0200 MIME-Version: 1.0 In-Reply-To: <20160530093204.GR29844@pali> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/05/2016 11:32, Pali Rohár wrote: > On Friday 27 May 2016 14:11:11 Gabriele Mazzotta wrote: >> On 22/05/2016 13:50, Pali Rohár wrote: >>> This patch exports standard hwmon pwmX_enable sysfs attribute for enabling >>> or disabling automatic fan control by BIOS. Standard value "1" is for >>> disabling automatic BIOS fan control and value "2" for enabling. >>> >>> Currently there is no way to check if BIOS auto mode is enabled (at least >>> it is not know how to do it), so hwmon sysfs attribute is write-only. >>> >>> By default BIOS auto mode is enabled by laptop firmware. >>> >>> When BIOS auto mode is enabled, custom fan speed value (set via hwmon pwmX >>> sysfs attribute) is overwritten by SMM in few seconds and therefore any >>> custom settings are without effect. So this is reason why implementing >>> option for disabling BIOS auto mode is needed. >>> >>> So finally this patch allows kernel to set and control fan speed on >>> laptops, but it can be dangerous (like setting speed of other fans). >>> >>> This new feature is highly experimental, uses Dell SMM calls, so does not >>> have to be supported by all laptops BIOSes. It was tested on Dell Latitude >>> E6440 with BIOS A5. >> >> Tested on a Dell XPS13 9333. Changing the value of pwm1_enable appears >> to have no effect here. > > Can you check what i8k_enable_fan_auto_mode() returns? Error code or not? No error. However, independently on the value I set, the BIOS always overrides the speed of the fan.