Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754061AbbL3AWI (ORCPT ); Tue, 29 Dec 2015 19:22:08 -0500 Received: from arroyo.ext.ti.com ([192.94.94.40]:55068 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753838AbbL3AWE (ORCPT ); Tue, 29 Dec 2015 19:22:04 -0500 Subject: Re: [PATCH 4/6] regulator: lp872x: Add enable GPIO pin support To: Paul Kocialkowski References: <1450868319-20513-1-git-send-email-contact@paulk.fr> <1450868319-20513-5-git-send-email-contact@paulk.fr> <20151223115632.GS16023@sirena.org.uk> <568088B4.6090207@ti.com> <1451342963.14631.13.camel@collins> <5681D7A8.2030101@ti.com> <1451387613.18148.9.camel@collins> CC: Mark Brown , , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Russell King , =?UTF-8?Q?Beno=c3=aet_Cousson?= , Tony Lindgren , Liam Girdwood , , , From: Milo Kim Message-ID: <568323B7.7080101@ti.com> Date: Wed, 30 Dec 2015 09:22:15 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <1451387613.18148.9.camel@collins> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3491 Lines: 84 Hi Paul, On 29/12/15 20:13, Paul Kocialkowski wrote: > Hi Milo, > > Le mardi 29 décembre 2015 à 09:45 +0900, Milo Kim a écrit : >> Hi Paul, >> >> On 29/12/15 07:49, Paul Kocialkowski wrote: >>> Hi Milo, thanks for the review, >>> >>> Le lundi 28 décembre 2015 à 09:56 +0900, Milo Kim a écrit : >>>> Hi Paul, >>>> >>>> On 23/12/15 20:56, Mark Brown wrote: >>>>> On Wed, Dec 23, 2015 at 11:58:37AM +0100, Paul Kocialkowski wrote: >>>>> >>>>>> + gpio = lp->pdata->enable_gpio; >>>>>> + if (!gpio_is_valid(gpio)) >>>>>> + return 0; >>>>>> + >>>>>> + /* Always set enable GPIO high. */ >>>>>> + ret = devm_gpio_request_one(lp->dev, gpio, GPIOF_OUT_INIT_HIGH, "LP872X EN"); >>>>>> + if (ret) { >>>>>> + dev_err(lp->dev, "gpio request err: %d\n", ret); >>>>>> + return ret; >>>>>> + } >>>>> >>>>> This isn't really adding support for the enable GPIO as the changelog >>>>> suggests, it's requesting but not managing the GPIO. Since there is >>>>> core support for manging enable GPIOs this seems especially silly, >>>>> please tell the core about the GPIO and then it will work at runtime >>>>> too. >>>>> >>>> >>>> With reference to my previous mail, external GPIOs for LDO3 and BUCK2 in >>>> LP8725 can be specified through regulator_config.ena_gpio. BUCK2 only >>>> can be controlled by external pin when CONFIG pin is grounded. >>>> >>>> Please see the description at page 5 of the datasheet. >>>> >>>> http://www.ti.com/lit/ds/symlink/lp8725.pdf >>> >>> After reading the datasheets thoroughly, it seems to me that for the >>> lp8720, the EN pin is used to enable the regulators output, which is a >>> good fit for the core regulator GPIO framework, as there is no reason to >>> keep it on when no regulator is in use. The serial interface is already >>> available when EN=0 and regulators can be configured in that state. The >>> lp8725 seems seems to behave the same when CONFIG=0 (the datasheet >>> clearly states: "CONFIG=0: EN=1 turns on outputs or standby mode if >>> EN=0"). On the other hand, it is indeed used as a power-on pin when >>> CONFIG=1. >> >> I think it's different use case. LP8720/5 are designed for system PMU, >> so some regulators are enabled by default after the device is on. EN pin >> is used for turning on/off the chip. This pin does not control regulator >> outputs directly. It's separate functional block in the silicon. > > Well, I really don't understand why the EN pin would turn on/off the > chip. All it does it enable the regulators outputs (by entering IDLE > mode), the serial block is already available in STANDBY state. > > If we want some regulators enabled at boot, the best thing to do seems > to be to request the GPIO with the GPIOF_INIT_HIGH flag, as done in e.g. > the max8952 regulator driver: > > if (pdata->reg_data->constraints.boot_on) > config.ena_gpio_flags |= GPIOF_OUT_INIT_HIGH; According to MAX8952 datasheet, output regulator is enabled/disabled using EN pin, so ena_gpio is used correctly. However, LP8720/5 regulators are enabled/disabled through I2C command. Only few regulators of LP8725 can be on/off by separate external pins. (B2_EN and LDO3_EN) Please note that EN pin in LP8720/5 is not the control pin for enabling/disabling regulators. Best regards, Milo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/