From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CBBCC49ED7 for ; Tue, 10 Sep 2019 19:07:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5DDF21479 for ; Tue, 10 Sep 2019 19:07:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kemnade.info header.i=@kemnade.info header.b="mEBIfoi6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727597AbfIJTH0 (ORCPT ); Tue, 10 Sep 2019 15:07:26 -0400 Received: from mail.andi.de1.cc ([85.214.55.253]:48152 "EHLO mail.andi.de1.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725797AbfIJTHZ (ORCPT ); Tue, 10 Sep 2019 15:07:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kemnade.info; s=20180802; h=Content-Type:MIME-Version:References: In-Reply-To:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=AEDjfrYYUhQdX6HMeGMCyoTKE7nAS03kl1QMQ2bdVZE=; b=mEBIfoi68woBxE9Faku/eplgd yOUOAxJqNJN1rFDopEdy7+rMcT4NKo9TvRp0UmRFxgvBNCepCYwBeT1NJzCJ2a/Tlu9JkowFA4dJ3 fyppG3GcpF4QxkNpHXt/P1ezPOI5ZDiw8Q//YQWapU0YdIvOKcIeDdlVHCfZseQ3AbZpA=; Received: from p200300ccff17ef007ee9d3fffe1fa246.dip0.t-ipconnect.de ([2003:cc:ff17:ef00:7ee9:d3ff:fe1f:a246] helo=eeepc) by mail.andi.de1.cc with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1i7lTt-0006RZ-5m; Tue, 10 Sep 2019 21:07:13 +0200 Received: from [::1] (helo=localhost) by eeepc with esmtp (Exim 4.89) (envelope-from ) id 1i7lTs-0001Px-6x; Tue, 10 Sep 2019 21:07:12 +0200 Date: Tue, 10 Sep 2019 21:06:48 +0200 From: Andreas Kemnade To: Daniel Thompson Cc: lee.jones@linaro.org, jingoohan1@gmail.com, jacek.anaszewski@gmail.com, pavel@ucw.cz, dmurphy@ti.com, robh+dt@kernel.org, mark.rutland@arm.com, b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org, "H. Nikolaus Schaller" Subject: Re: [PATCH 1/2] backlight: lm3630a: add an enable gpio for the HWEN pin Message-ID: <20190910210648.3594912d@kemnade.info> In-Reply-To: <20190910102156.vmprsjebmlphkv34@holly.lan> References: <20190908203704.30147-1-andreas@kemnade.info> <20190908203704.30147-2-andreas@kemnade.info> <20190909105729.w5552rtop7rhghy2@holly.lan> <20190909221349.46ca5a1f@aktux> <20190910102156.vmprsjebmlphkv34@holly.lan> X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; i686-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/d51yUFk84RybqHzz4cluJyL"; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Sig_/d51yUFk84RybqHzz4cluJyL Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 10 Sep 2019 11:21:56 +0100 Daniel Thompson wrote: [...] > > > Is this needed? > > >=20 > > > This is a remove path, not a power management path, and we have no id= ea > > > what the original status of the pin was anyway? > > > =20 > >=20 > > Looking at Ishdn on page 5 of the datasheet, switching it off everytime > > possible seems not needed. We would need to call chip_init() everytime > > we enable the gpio or live with default values. > > Therefore I did decide to not put it into any power management path. > > But switching it on and not switching it off feels so unbalanced. =20 >=20 > Either the power consumed by the controller when strings aren't lit up > matters, in which case the driver should implement proper power > management or it doesn't matter and changing the pin state isn't needed. >=20 > I'm happy with either of the above but this looks like a third way, > where eager users could hack in a bit of extra power management by > forcing drivers to unbind.=20 >=20 I think I will take the simple way. I am quite sure that the power consumption with HWEN on and leds off does not matter. If someone later comes up and finds out that I misread the datasheet, things are prepared to be improved. At least the hardware can be properly described in the devicetree. 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