From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752517AbcKHNvd (ORCPT ); Tue, 8 Nov 2016 08:51:33 -0500 Received: from hqemgate14.nvidia.com ([216.228.121.143]:13313 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750724AbcKHNva (ORCPT ); Tue, 8 Nov 2016 08:51:30 -0500 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 08 Nov 2016 05:51:28 -0800 Message-ID: <5821D49E.2070308@nvidia.com> Date: Tue, 8 Nov 2016 19:05:26 +0530 From: Laxman Dewangan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Linus Walleij CC: "thierry.reding@gmail.com" , Stephen Warren , Rob Herring , Mark Rutland , Jon Hunter , Masahiro Yamada , "linux-gpio@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] pinctrl: tegra: Add driver to configure voltage and power of io pads References: <1478077742-25437-1-git-send-email-ldewangan@nvidia.com> <1478077742-25437-3-git-send-email-ldewangan@nvidia.com> <58201401.8050805@nvidia.com> <5821A6D3.7010000@nvidia.com> In-Reply-To: X-Originating-IP: [10.19.65.30] X-ClientProxiedBy: DRUKMAIL102.nvidia.com (10.25.59.20) To bgmail102.nvidia.com (10.25.59.11) Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 08 November 2016 06:59 PM, Linus Walleij wrote: > On Tue, Nov 8, 2016 at 11:20 AM, Laxman Dewangan wrote: >> On Tuesday 08 November 2016 03:45 PM, Linus Walleij wrote: >>> If you can *actually* change the volatage, it needs to be modeled >>> as a (fixed voltage?) regulator, not as a custom property for the pin >>> control attributes. I guess you definiately need the regulator framework >>> to accumulate and infer the different consumer requirements anyway >>> in that case. >> The PMIC voltage output is changed via regulator calls. >> Here, we need to have two configruations for given voltage level of >> interface: >> * One at IO voltage from PMIC via regulator call to change votlage of IO >> rail. >> * Second, configure the IO pad register to tell the IO voltage level so that >> it can configured internally for that level. > I understand! (I think.) Thanks, > > But then the two things (A) changing the regulator voltage and (B) changing > the pin setting need to happen at the same time do they > not? > > Now you're just hardcoding something into these device tree properties > and hoping that the regulators will somehow be set up in accordance to > what you set up for the pads in the device tree, correct? There is two types of configuration in given platform, the IO voltage does not get change (fixed in given platform) and in some of cases, get change dynamically like SDIO3.0 where the voltage switches to 3.3V and 1.8V. Yes, it can be integrated with the regulator handle and then it can call the required configurations through notifier and regulator_get_voltage(). But I think it is too much complex for the static configurations. This mandate also to populate the regulator handle and all power tree. The simple way for static configuration (case where voltage does not get change), just take the power tree IO voltage from DT and configure the IO pad control register. For dynamic case, there is some sequence need to be followed based on voltage direction change (towards lower or towards higher) for the voltage change and the IO pad voltage configuration and it is simple to do it from client driver. > > To me it seems like the pins/pads should all have an <&phandle> to > the regulator controlling its voltage output, in the device tree. > > In the Linux kernel, the driver has to regulator_[bulk_]get() this for > each pin, check the voltage with regulator_get_voltage() and set up > this according to the supplied voltage. > > The driver then ideally should subscribe to regulator voltage notifier > events to change the setting if the voltage changes. I guess. But > atleast the first step seems inevitable: get the voltage from a regulator. > > Else there is no dependency between the regulator and its consumer. > > So what your pins need is a regulator phandle, not a magic value to > be poked into a register, hoping things will match up. > > I understand that this is a simple quick-and-dirty solution but it is > not the right solution. Yaah, the static power tree configuration is much simple in this approach without having regulator drivers and support. Integrating with regulator driver can be done here also. I like to have both approach, through pinmux DT and also from regulator. So based on the platform, if regulator supported then populate required properties in DT for regulator else go on standard pinmux DT way (for non-regulator cases). Need your opinion?