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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BC86C4708E for ; Wed, 4 Jan 2023 09:03:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233421AbjADJCk (ORCPT ); Wed, 4 Jan 2023 04:02:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238660AbjADJBg (ORCPT ); Wed, 4 Jan 2023 04:01:36 -0500 Received: from mx1.tq-group.com (mx1.tq-group.com [93.104.207.81]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BFE4B1E; Wed, 4 Jan 2023 01:00:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1672822849; x=1704358849; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=+sboQuLLf8L8vEbmebrmtcbyrXlcTdugHxJikNm8Nas=; b=UchXKTskI8XRyYGWphksix3qJD0sItDJbGlDWZv6vYC0Ar15iQIu/PNY AUUrNEypVt/IFvUr6Dof9RUgF14Y0IEjBK4H5MZdXd4EvVhossxUigGUQ OakS2UWyIJZ4wYCa1PwTkiziVuSzDicrhV52XVYyTpA69GRkMUciyABUF 8byFo1b83lyvnZQLp7lfYsHPevkFFC9C2fix58vrVS5RLq/59PQJkrqdC RMjdRwyoZr3BfrhLIfxGWtZjf2zKo0Ba0VXshiddN9lvNG1NXAm2QIX5p FcRnHAam8JACUeSJKuRSaZ28Ha0XSwiIjYjzYE0Xairpalzy6sSs1S3PA g==; X-IronPort-AV: E=Sophos;i="5.96,299,1665439200"; d="scan'208";a="28235618" Received: from unknown (HELO tq-pgp-pr1.tq-net.de) ([192.168.6.15]) by mx1-pgp.tq-group.com with ESMTP; 04 Jan 2023 10:00:46 +0100 Received: from mx1.tq-group.com ([192.168.6.7]) by tq-pgp-pr1.tq-net.de (PGP Universal service); Wed, 04 Jan 2023 10:00:46 +0100 X-PGP-Universal: processed; by tq-pgp-pr1.tq-net.de on Wed, 04 Jan 2023 10:00:46 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1672822846; x=1704358846; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=+sboQuLLf8L8vEbmebrmtcbyrXlcTdugHxJikNm8Nas=; b=bEOldYHQoFwbGIPMPbW0sb5HKcXfH182EsXQrP6Bw8EF9XFCI7Y77XR6 4eDtYxn56+hlLC5dNR5Nyjt/4iwoXrsjYwDAoMXtaFfZWDiBfkwNTuYtY 29NkQiXj+asc8iCrzdejPX6+1kgSTvtIJcKygcxE04b6Q7/Zvl46Fp6Th R4y6+/gMVm8Cs6cUBdb2/uuy73zFNEA27tgZybqxe7H6DAB7x7qAl64pY VzlexG5Zlmz1DSEEbcVxFdpL/GonqxcKt1omZPqBPwhc5+tphw+eLmhB8 LZ1a3/zHk/83K4DcUVEYIELNHsHoH6hU69GBsEEQjO1X7dgmYIIFSO9Mi g==; X-IronPort-AV: E=Sophos;i="5.96,299,1665439200"; d="scan'208";a="28235617" Received: from vtuxmail01.tq-net.de ([10.115.0.20]) by mx1.tq-group.com with ESMTP; 04 Jan 2023 10:00:45 +0100 Received: from steina-w.localnet (unknown [10.123.53.21]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by vtuxmail01.tq-net.de (Postfix) with ESMTPSA id 9DF8D280056; Wed, 4 Jan 2023 10:00:45 +0100 (CET) From: Alexander Stein To: Doug Anderson , Matthias Kaehlcke Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Stefan Wahren , stable@vger.kernel.org, Ravi Chandra Sadineni , Icenowy Zheng Subject: Re: [PATCH v2 1/2] usb: misc: onboard_usb_hub: Don't create platform devices for DT nodes without 'vdd-supply' Date: Wed, 04 Jan 2023 10:00:43 +0100 Message-ID: <10807929.5MRjnR8RnV@steina-w> Organization: TQ-Systems GmbH In-Reply-To: References: <20221222022605.v2.1.If5e7ec83b1782e4dffa6ea759416a27326c8231d@changeid> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi Matthias, Am Dienstag, 3. Januar 2023, 18:12:24 CET schrieb Matthias Kaehlcke: > On Thu, Dec 22, 2022 at 11:26:26AM -0800, Doug Anderson wrote: > > Hi, > > > > On Wed, Dec 21, 2022 at 6:26 PM Matthias Kaehlcke wrote: > > > The primary task of the onboard_usb_hub driver is to control the > > > power of an onboard USB hub. The driver gets the regulator from the > > > device tree property "vdd-supply" of the hub's DT node. Some boards > > > have device tree nodes for USB hubs supported by this driver, but > > > don't specify a "vdd-supply". This is not an error per se, it just > > > means that the onboard hub driver can't be used for these hubs, so > > > don't create platform devices for such nodes. > > > > > > This change doesn't completely fix the reported regression. It > > > should fix it for the RPi 3 B Plus and boards with similar hub > > > configurations (compatible DT nodes without "vdd-supply"), boards > > > that actually use the onboard hub driver could still be impacted > > > by the race conditions discussed in that thread. Not creating the > > > platform devices for nodes without "vdd-supply" is the right > > > thing to do, independently from the race condition, which will > > > be fixed in future patch. > > > > > > Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver") > > > Link: > > > https://lore.kernel.org/r/d04bcc45-3471-4417-b30b-5cf9880d785d@i2se.com > > > / Reported-by: Stefan Wahren > > > Signed-off-by: Matthias Kaehlcke > > > --- > > > > > > Changes in v2: > > > - don't create platform devices when "vdd-supply" is missing, > > > > > > rather than returning an error from _find_onboard_hub() > > > > > > - check for "vdd-supply" not "vdd" (Johan) > > > - updated subject and commit message > > > - added 'Link' tag (regzbot) > > > > > > drivers/usb/misc/onboard_usb_hub_pdevs.c | 13 +++++++++++++ > > > 1 file changed, 13 insertions(+) > > > > I'm a tad bit skeptical. > > > > It somehow feels a bit too much like "inside knowledge" to add this > > here. I guess the "onboard_usb_hub_pdevs.c" is already pretty > > entangled with "onboard_usb_hub.c", but I'd rather the "pdevs" file > > keep the absolute minimum amount of stuff in it and all of the details > > be in the other file. > > > > If this was the only issue though, I'd be tempted to let it slide. As > > it is, I'm kinda worried that your patch will break Alexander Stein, > > who should have been CCed (I've CCed him now) or Icenowy Zheng (also > > CCed now). I believe those folks are using the USB hub driver > > primarily to drive a reset GPIO. Looking at the example in the > > bindings for one of them (genesys,gl850g.yaml), I even see that the > > reset-gpio is specified but not a vdd-supply. I think you'll break > > that? > > Thanks for pointing that out. My assumption was that the regulator is > needed for the driver to do anything useful, but you are right, the > reset GPIO alone could be used in combination with an always-on regulator > to 'switch the hub on and off'. > > > In general, it feels like it should actually be fine to create the USB > > hub driver even if vdd isn't supplied. Sure, it won't do a lot, but it > > shouldn't actively hurt anything. You'll just be turning off and on > > bogus regulators and burning a few CPU cycles. I guess the problem is > > some race condition that you talk about in the commit message. I'd > > rather see that fixed... > > Yes, the race conditions needs to be fixed as well, I didn't have enough > time to write and test a patch before taking a longer break for the > holidays, so I only sent out this (supposed) partial mitigation. > > > That being said, if we want to be more efficient and not burn CPU cycles > > and memory in Stefan Wahren's case, maybe the USB hub driver itself could > > return a canonical error value from its probe when it detects that it has > > no useful job and then "onboard_usb_hub_pdevs" could just silently bail > > out? > > _probe() could return an error, however onboard_hub_create_pdevs() can't > rely on that, since the actual onboard_hub driver might not have been > loaded yet when the function is called. > > It would be nice not to instantiate the pdev and onboard_hub USB instances > if the DT node has neither a 'vdd-supply' nor 'reset-gpios'. If we aren't > ok with doing that in onboard_hub_create_pdevs() then at least the 'raw' > platform device would be created. onboard_hub_probe() could still > bail if both properties are absent, _find_onboard_hub() would have to > check it again to avoid the deferred probing 'loop' for the USB instances. I'm not really fond of checking for optional features like 'vdd-supply' and 'reset-gpios'. This issue will pop up again if some new optional feature is added again, e.g. power-domains. > Alternatively we could 'just' fix the race condition involving the 'attach > work' and the onboard_hub driver is fully instantiated even on (certain) > boards where it does nothing. It's relatively rare that USB hub nodes are > specified in the DT (unless the intention is to use this driver) and > CONFIG_USB_ONBOARD_HUB needs to be set for the instances to be created, > so maybe creating the useless instances is not such a big deal. IMHO creating a pdev shouldn't harm in any case. It's similar to having a DT node without a corresponding driver enabled or even existing. Also adding USB devices to DT is something which is to be expected. usb-device.yaml exists since 2020 and the txt version since 2016. Unfortunately I'm not able to reproduce this issue on a different platform where the same HUB but no reset-gpios is required. I also noticed that onboard-usb-hub raises the error > Failed to attach USB driver: -22 for each hub it is supposed to support. Best regards, Alexander