From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] ACPICA: Export mutex functions Date: Mon, 17 Apr 2017 14:03:53 -0700 Message-ID: <20170417210353.GA19771@roeck-us.net> References: <1492009990-3539-1-git-send-email-linux@roeck-us.net> <94F2FBAB4432B54E8AACC7DFDE6C92E37E5924DB@ORSMSX110.amr.corp.intel.com> <20170412212241.GA12384@roeck-us.net> <1AE640813FDE7649BE1B193DEA596E886CE92A85@SHSMSX101.ccr.corp.intel.com> <20170417155646.GA8730@roeck-us.net> <94F2FBAB4432B54E8AACC7DFDE6C92E37E59332C@ORSMSX110.amr.corp.intel.com> <94F2FBAB4432B54E8AACC7DFDE6C92E37E59345B@ORSMSX110.amr.corp.intel.com> <20170417194527.GA16734@roeck-us.net> <94F2FBAB4432B54E8AACC7DFDE6C92E37E593580@ORSMSX110.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:43070 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852AbdDQVD4 (ORCPT ); Mon, 17 Apr 2017 17:03:56 -0400 Content-Disposition: inline In-Reply-To: <94F2FBAB4432B54E8AACC7DFDE6C92E37E593580@ORSMSX110.amr.corp.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Moore, Robert" Cc: "Zheng, Lv" , "Wysocki, Rafael J" , 'Len Brown' , "'linux-acpi@vger.kernel.org'" , "'devel@acpica.org'" , "'linux-kernel@vger.kernel.org'" , "Box, David E" On Mon, Apr 17, 2017 at 08:40:38PM +0000, Moore, Robert wrote: > > > > -----Original Message----- > > From: Guenter Roeck [mailto:linux@roeck-us.net] > > Sent: Monday, April 17, 2017 12:45 PM > > To: Moore, Robert > > Cc: Zheng, Lv ; Wysocki, Rafael J > > ; 'Len Brown' ; 'linux- > > acpi@vger.kernel.org' ; 'devel@acpica.org' > > ; 'linux-kernel@vger.kernel.org' > kernel@vger.kernel.org>; Box, David E > > Subject: Re: [PATCH] ACPICA: Export mutex functions > > > > On Mon, Apr 17, 2017 at 07:27:37PM +0000, Moore, Robert wrote: > > > > > > > -----Original Message----- > > > > From: Moore, Robert > > > > Sent: Monday, April 17, 2017 10:13 AM > > > > To: Guenter Roeck ; Zheng, Lv > > > > > > > > Cc: Wysocki, Rafael J ; Len Brown > > > > ; linux-acpi@vger.kernel.org; devel@acpica.org; > > > > linux- kernel@vger.kernel.org > > > > Subject: RE: [PATCH] ACPICA: Export mutex functions > > > > > > > > There is a model for the drivers to directly acquire an AML mutex > > > > object. That is why the acquire/release public interfaces were added > > > > to ACPICA. > > > > > > > > I forget all of the details, but the model was developed with MS and > > > > others during the ACPI 6.0 timeframe. > > > > > > > > > > > [Moore, Robert] > > > > > > > > > Here is the case where the OS may need to directly acquire an AML > > mutex: > > > > > > From the ACPI spec: > > > > > > 19.6.2 Acquire (Acquire a Mutex) > > > > > > Note: For Mutex objects referenced by a _DLM object, the host OS may > > also contend for ownership. > > > > > From the context in the dsdt, and from description of expected use cases > > for _DLM objects I can find, this is what the mutex is used for (to > > serialize access to a resource on a low pin count serial interconnect, > > aka LPC). > > > > What does that mean in practice ? That I am not supposed to use it > > because it doesn't follow standard ACPI mutex declaration rules ? > > > > Thanks, > > Guenter > > > > > > [Moore, Robert] > > I'm not an expert on the _DLM method, but I would point you to the description section in the ACPI spec, 5.7.5 _DLM (DeviceLock Mutex). > I did. However, not being an ACPI expert, that doesn't tell me anything. Guenter > > > > > > > > > > > Other than this case, the OS/drivers should never need to directly > > acquire an AML mutex. > > > Bob > > >