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=-9.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 C0D57C433E6 for ; Wed, 10 Feb 2021 21:06:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8EB9864ECF for ; Wed, 10 Feb 2021 21:06:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232957AbhBJVFp (ORCPT ); Wed, 10 Feb 2021 16:05:45 -0500 Received: from mail-wm1-f53.google.com ([209.85.128.53]:50221 "EHLO mail-wm1-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232103AbhBJVFi (ORCPT ); Wed, 10 Feb 2021 16:05:38 -0500 Received: by mail-wm1-f53.google.com with SMTP id 190so3067124wmz.0; Wed, 10 Feb 2021 13:05:21 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=2TDlg5kjQ/FiLU6fnovw1yongTK1pX31S0OpLZGyLWg=; b=TOJtLrRKBK2DT9E+OxSKWPiVTt5PUV4EwCyND0ro8YRjm41R6dXTjB/XGMyJRjZM5a WUY/6e3rW7LL1bJ8SYsisNBfMHY5gz0JoMO6/F1rDvgAX0uI7iwofMzAO1o4wBZqPYFa oqE6Oipf34aC/C7V3gsIkHSZrS1s5GeQqRBjrbp4nWcVRsNjF/IF72qM9NHy5mesbdgH njtuBowsoYEQ6cmk6uzIiFpnKV+e8HVSbPGgeLl5elokhW0oFA9B/NCYcvzXWyiYbB+x PIzxCCmRxy+IlxKyHn0eY9RLmsebCmHxzfyfxRTpLO/HBCYiarXZD19j0Oqa2WkfX6rQ fLHA== X-Gm-Message-State: AOAM530mOd8eZYRs+119t1fBuKocDnnxprFPsbw0vp/GQ/q4p/9YeZi1 QTDEnP+CTPaKtFzJ8u8RwXE= X-Google-Smtp-Source: ABdhPJzU6v3Y59YhX2bXBM8NSYFzwjKrJ+YlvSb1W4JYumBTJJMDV+0v5geobBTZEgmiwsMEvzcsmQ== X-Received: by 2002:a1c:dd55:: with SMTP id u82mr914409wmg.135.1612991095811; Wed, 10 Feb 2021 13:04:55 -0800 (PST) Received: from kozik-lap (adsl-84-226-167-205.adslplus.ch. [84.226.167.205]) by smtp.googlemail.com with ESMTPSA id s23sm4554534wmc.29.2021.02.10.13.04.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Feb 2021 13:04:53 -0800 (PST) Date: Wed, 10 Feb 2021 22:04:51 +0100 From: Krzysztof Kozlowski To: Matthias Kaehlcke Cc: Greg Kroah-Hartman , Rob Herring , Frank Rowand , devicetree@vger.kernel.org, Peter Chen , Stephen Boyd , Alan Stern , Ravi Chandra Sadineni , Bastien Nocera , linux-kernel@vger.kernel.org, Douglas Anderson , linux-usb@vger.kernel.org, Al Cooper , "Alexander A. Klimov" , Andy Gross , Bjorn Andersson , Masahiro Yamada , Mathias Nyman , linux-arm-msm@vger.kernel.org Subject: Re: [PATCH v5 0/4] USB: misc: Add onboard_usb_hub driver Message-ID: <20210210210451.3coi62cynptzb6wf@kozik-lap> References: <20210210171040.684659-1-mka@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210210171040.684659-1-mka@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Feb 10, 2021 at 09:10:35AM -0800, Matthias Kaehlcke wrote: > This series adds the onboard_usb_hub_driver, the corresponding > device tree bindings and creation of onboard_usb_hub platform in > the xhci-plat driver during probe(). > > The main issue the driver addresses is that a USB hub needs to be > powered before it can be discovered. For discrete onboard hubs (an > example for such a hub is the Realtek RTS5411) this is often solved > by supplying the hub with an 'always-on' regulator, which is kind > of a hack. It seems you are re-developing the power sequence drivers which perform exactly this. Peter Chen some time ago was bringing power sequence to USB devices, but I lost track where this ended up. Some of his (and my) very old work (2017...) can be found here: https://github.com/krzk/linux/tree/wip/odroid-u3-usb3503-pwrseq Instead of adding custom driver hiding some USB hub implementation, power sequence seems a generic solution. What if you need to power cycle other embedded USB device? Not a hub? I was not aware of previous discussions so maybe I am repeating someone. Best regards, Krzysztof