From mboxrd@z Thu Jan 1 00:00:00 1970 From: Charles Garcia-Tobin Subject: Re: [RFC PATCH 0/4] Add ACPI support for pinctrl configuration Date: Tue, 5 Apr 2016 08:56:12 +0000 Message-ID: References: <1459424685-26965-1-git-send-email-irina.tirdea@intel.com> <20160404225200.GA1615@svinekod> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160404225200.GA1615@svinekod> Sender: linux-acpi-owner@vger.kernel.org To: Mark Rutland , Irina Tirdea Cc: "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 , Octavian Purdila , Cristina Ciocan , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On 04/04/2016 23:52, "Mark Rutland" wrote: >Hi, > >On Thu, Mar 31, 2016 at 02:44:41PM +0300, Irina Tirdea wrote: >> This is a proposal for adding ACPI support for pin controller >> configuration. >> >> It has been developed to enable the MinnowBoard and IoT community >> by providing an easy way to specify pin multiplexing and >> pin configuration. >> >> This proposal is based on using _DSD properties to specify device >> states and configuration nodes and it follows closely the device >> tree model. Device states are defined using the Device Properties >> format and the configuration nodes are defined using the >> Hierarchical Properties Extension format. The generic properties >> for the configuration nodes are the same as the ones for device >> tree, while pincontroller drivers can also define custom ones. > >>From a look of the Documentation addition, and of the current uses of >pinctrl-names in device tree bindings, one reason for requiring multiple >pinctrl states is power management. Given that, I'm somewhat concerned by >this, >as it goes against the usual ACPI model of abstracting this sort of thing >behind power control methods. > >To the best of my knowledge, that goes against the ASWG's expectations on >how >_DSD will be used (per [1]). Charles, please correct me if that document >is no >longer representative. It is though latest version was posted by Rafael a bit later: https://lists.acpica.org/pipermail/dsd/2015-December/000027.html In addition the core rules requiring that existing ACPI paradigms are not subverted through DSD (basically the concern you express) are also documented in the main DSD documentation itself: http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UU ID.pdf (section 2.3) Cheers Charles > >Additionally, pinctrl has some cross-cutting concerns (e.g. mutually >exclusive >device usage due to a shared pin), and I can imagine that may interact >poorly >with any AML or firmware assumptions about the state of the world, as >there's >no mechanism present to notify those of changes to pins. > >I think that this is a class of problem which needs to be raised with the >ASWG, >and solved in an ACPI-native fashion, rather than simply copying >properties >from DT using _DSD. If nothing else, the restrictions on FW and AML would >need >to be specified. > >Thanks, >Mark. > >[1] https://lists.acpica.org/pipermail/dsd/2015-September/000019.html >