From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756283AbcAOJQK (ORCPT ); Fri, 15 Jan 2016 04:16:10 -0500 Received: from mail-pf0-f193.google.com ([209.85.192.193]:35737 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751112AbcAOJP2 (ORCPT ); Fri, 15 Jan 2016 04:15:28 -0500 Subject: Re: [PATCH v2 06/12] mmc: pwrseq: add support for power-on sequencing through DT To: Javier Martinez Canillas References: <1452155155-16232-1-git-send-email-wxt@rock-chips.com> <1452155155-16232-7-git-send-email-wxt@rock-chips.com> <568FAA07.1010509@osg.samsung.com> <6960259.dpUH8KWsNS@phil> <5693D226.2000307@osg.samsung.com> Cc: Heiko Stuebner , Ulf Hansson , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, leecam@google.com, keescook@google.com, NeilBrown , Srinivas Kandagatla , Alexandre Courbot , leozwang@google.com, Caesar Wang From: Caesar Wang Message-ID: <5698B8A9.9040002@gmail.com> Date: Fri, 15 Jan 2016 17:15:21 +0800 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: <5693D226.2000307@osg.samsung.com> 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 Hi Javier, 在 2016年01月12日 00:02, Javier Martinez Canillas 写道: > Hello Heiko, > > On 01/08/2016 11:42 PM, Heiko Stuebner wrote: >> Am Freitag, 8. Januar 2016, 09:22:31 schrieb Javier Martinez Canillas: >>>> For example: >>>> we need enable wifi module power to via the WL_REG_ON >>>> pin, we need enable it as the regulator if this pin is connected to >>>> the gpio of cpu. >>> This part confuses me, so does your chip have an actual regulator that >>> needs to be enabled or is just a fake regulator whose gpio property is >>> used not to enable the regulator but to toggle the WL_REG_ON pin of >>> the WiFi chip? >> another option would be to use the reset-gpio-handles. rk3288-veyron and I >> think some Exynos as well use it that way. >> > Yes I know, my point was that the reset-gpios property should be used > instead of a fake regulator if what's needed is to toggle a chip pin. > >>>> Maybe, someone will say that can pull up/down from dts. >>>> Unfortunately some SoCs can't support pinctrl pull up/down in >>>> internal. >>> Can you please elaborate on this? AFAIU this limitation is the reason >>> why you went with the regulator approach so I think it deserve a more >>> deep explanation. >> On the rk3036 each pin has an individual unchangable pull direction. So it's >> either no bias or pulling in the predefined direction (the pin_default bias >> option). >> > I think each change has to be justified on its own so I would say that > having a regulator enabled as a part of a SDIO chip's power sequencing > is something needed for many platforms, and that this provider should > be extended to support that (something like commit msg in patch 05/12). > > And then in the kylin DTS change (patch 08/12), I would explain why a > chained regulators approach is used/needed instead of the reset-gpios > due any platform limitations. Okay, I 'm agreed with your points in here. The reset-gpios/pwrsq can meet the demand of some wlan chips trigger condition. No matter whatever is the BT_EN or WL_EN triggers pin. >> Heiko >> > Best regards, -- Thanks, Caesar