Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760674AbcDFABm (ORCPT ); Tue, 5 Apr 2016 20:01:42 -0400 Received: from foss.arm.com ([217.140.101.70]:54246 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754007AbcDFABk (ORCPT ); Tue, 5 Apr 2016 20:01:40 -0400 Date: Wed, 6 Apr 2016 01:01:33 +0100 From: Mark Rutland To: Octavian Purdila Cc: "Tirdea, Irina" , "Rafael J. Wysocki" , Len Brown , Mika Westerberg , Linus Walleij , "linux-gpio@vger.kernel.org" , "linux-acpi@vger.kernel.org" , Rob Herring , Heikki Krogerus , Andy Shevchenko , "Ciocan, Cristina" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "charles.garcia-tobin@arm.com" Subject: Re: [RFC PATCH 0/4] Add ACPI support for pinctrl configuration Message-ID: <20160406000130.GB8903@svinekod> References: <1459424685-26965-1-git-send-email-irina.tirdea@intel.com> <20160404225200.GA1615@svinekod> <1F3AC3675D538145B1661F571FE1805F2F2342A6@irsmsx105.ger.corp.intel.com> <20160405181625.GA3064@svinekod> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1729 Lines: 39 On Tue, Apr 05, 2016 at 11:09:34PM +0300, Octavian Purdila wrote: > On Tue, Apr 5, 2016 at 9:16 PM, Mark Rutland wrote: > > * The firmware is to some extent expected to manage pinctrl today (for power > > management of devices it does know about), and hence a pinctrl device is > > potentially under shared management of ACPI and the OS. > > > > * The ACPI specification says nothing about this style of pinctrl management, > > so it is unclear what the expectations are: > > Does it say anything at all about pinctrl management? To the best of my knowledge the ACPI spec does not explicitly mention pinctrl. In another reply it was mentioned that there is work in progress for pinmuxing, so evidently it is on the ASWG radar and within the scope of ACPI. I was trying to point out that it is _implicitly_ firmware's responsibility to do any pinctrl today, due to the ACPI model for power management, and the lack of an existing ACPI mechanisms to provide pinctrl data. In practice, firmware configures pinctrl at boot, and may modify pinctrl as part of the runtime power management firmware is put in charge of. The lack of any statement about pinctrl would mean that there is effectively no reasonable limitation on what firmware might do with pinctrl, and we cannot assume specific behaviour from the firmware. [...] > Since our focus is for open-ended configurations and for hardware that > it is not know to firmware we only considered the case where the pins > are not touched after the system boots. > > Now I wonder what are the cases were the firmware changes the pin > configuration after boot. Device power management and suspend/resume seem like the obvious cases. Thanks, Mark