Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752969AbbL2ApX (ORCPT ); Mon, 28 Dec 2015 19:45:23 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:54355 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257AbbL2ApV (ORCPT ); Mon, 28 Dec 2015 19:45:21 -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> 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: <5681D7A8.2030101@ti.com> Date: Tue, 29 Dec 2015 09:45:28 +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: <1451342963.14631.13.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: 2730 Lines: 67 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. On the other hand, 'ena_gpio' is used for each regulator control itself. For example, WM8994 has two LDOs which are controlled by external pins. LDOs are enabled/disabled through LDO1ENA and LDO2ENA pins. In this case, 'ena_gpio' is used. http://www.cirrus.com/en/pubs/proDatasheet/WM8994_v4.4.pdf (please refer to page 224 and 225) 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/