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 2563AC53210 for ; Mon, 2 Jan 2023 14:38:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232824AbjABOit (ORCPT ); Mon, 2 Jan 2023 09:38:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232614AbjABOiX (ORCPT ); Mon, 2 Jan 2023 09:38:23 -0500 Received: from mx1.tq-group.com (mx1.tq-group.com [93.104.207.81]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0121300; Mon, 2 Jan 2023 06:38:21 -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=1672670302; x=1704206302; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=nS3cdjPCgxeWFQVGp6kkWcgS22f4xwfU4K6Ctd7cTms=; b=oYWf+GfQ6qerBMn/bTPt7tem6AzHkm285PPGqk2K92Xn6aVr04myBNRF eC65c03RRJVy/WbaurdrtMPekl4n9ef2uvcPshKNfGAAb+ESAWyHnA2yh 9Ae34nqZ5IkvtN7Yp1UgJhTJZdkbm0SOCySR57XPKhhq5M9weMfIyJO77 41Gnbo4lNOsBjnNOW7EgyUoIHm9MfXlzl2vOBNZGsP7iPAcSPYIoXCybD cIQfnBCiPombdD/592NMPOQbbcQYeFh1EqPVI4MaYf5lk2e4hOUcQRgP0 ujknk/m+VqAF/YFt7s++mN9yBzoVBBMvWBgfXi7H+tHqThDAjDWFhLF1l A==; X-IronPort-AV: E=Sophos;i="5.96,294,1665439200"; d="scan'208";a="28206221" Received: from unknown (HELO tq-pgp-pr1.tq-net.de) ([192.168.6.15]) by mx1-pgp.tq-group.com with ESMTP; 02 Jan 2023 15:38:19 +0100 Received: from mx1.tq-group.com ([192.168.6.7]) by tq-pgp-pr1.tq-net.de (PGP Universal service); Mon, 02 Jan 2023 15:38:20 +0100 X-PGP-Universal: processed; by tq-pgp-pr1.tq-net.de on Mon, 02 Jan 2023 15:38:20 +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=1672670299; x=1704206299; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=nS3cdjPCgxeWFQVGp6kkWcgS22f4xwfU4K6Ctd7cTms=; b=Lfs1+oj2lWB6O+HBqVOIYFZieNP4UIPe3F87t6OyyHvNFJydeeMtu6Nh i2mmJrB/x6ZwhkdBDLXbgLkWDJT90eNAgS0iSAR+r2GB+hCWUwcLGafnL Qn4MHXtyBZ3AJdDTrG2klMMQfH66czVbUkqw8j6YjUgwXihLE+kP5IVFS CcAFWcXK0kJ6d3de921LYSuYbmHKTTpFaLLzz41eHT40VzK6BWPM01Rzn aopd7wzuOtrpd7Di3LxKvH1+6al+g4H1vkFS9JtQq8fmS2J++V/zEmYFD 0uwxFEdRMb09woaRWDdCXvtAANBzSrs+j0GdGpivcerpvz4B3P2SMNGR6 g==; X-IronPort-AV: E=Sophos;i="5.96,294,1665439200"; d="scan'208";a="28206220" Received: from vtuxmail01.tq-net.de ([10.115.0.20]) by mx1.tq-group.com with ESMTP; 02 Jan 2023 15:38:19 +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 AAAE6280056; Mon, 2 Jan 2023 15:38:19 +0100 (CET) From: Alexander Stein To: Doug Anderson , Matthias Kaehlcke , Icenowy Zheng , Stefan Wahren Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, stable@vger.kernel.org, Ravi Chandra Sadineni Subject: Re: [PATCH v2 1/2] usb: misc: onboard_usb_hub: Don't create platform devices for DT nodes without 'vdd-supply' Date: Mon, 02 Jan 2023 15:38:19 +0100 Message-ID: <1783674.3VsfAaAtOV@steina-w> Organization: TQ-Systems GmbH In-Reply-To: References: <20221222022605.v2.1.If5e7ec83b1782e4dffa6ea759416a27326c8231d@changeid> <3724284.kQq0lBPeGt@steina-w> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi Stefan, Am Montag, 2. Januar 2023, 12:44:33 CET schrieb Stefan Wahren: > Hello Alexander, >=20 > Am 02.01.23 um 10:20 schrieb Alexander Stein: > > Hi everybody, > >=20 > > Am Freitag, 23. Dezember 2022, 08:46:45 CET schrieb Icenowy Zheng: > >> =E5=9C=A8 2022-12-22=E6=98=9F=E6=9C=9F=E5=9B=9B=E7=9A=84 11:26 -0800= =EF=BC=8CDoug Anderson=E5=86=99=E9=81=93=EF=BC=9A > >>=20 > >>> Hi, > >>>=20 > >>> On Wed, Dec 21, 2022 at 6:26 PM Matthias Kaehlcke > >>>=20 > >>> 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. > >>>>=20 > >>>> 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. > >>>>=20 > >>>> 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 > >>>> --- > >>>>=20 > >>>> Changes in v2: > >>>> - don't create platform devices when "vdd-supply" is missing, > >>>>=20 > >>>> rather than returning an error from _find_onboard_hub() > >>>>=20 > >>>> - check for "vdd-supply" not "vdd" (Johan) > >>>> - updated subject and commit message > >>>> - added 'Link' tag (regzbot) > >>>>=20 > >>>> drivers/usb/misc/onboard_usb_hub_pdevs.c | 13 +++++++++++++ > >>>> 1 file changed, 13 insertions(+) > >>>=20 > >>> I'm a tad bit skeptical. > >>>=20 > >>> 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. > >>>=20 > >>> 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? > >>=20 > >> Well technically in my final DT a regulator is included (to have the > >> Vbus enabled when enabling the hub), however I am still against this > >> patch, because the driver should work w/o vdd-supply (or w/o reset- > >> gpios), and changing this behavior is a DT binding stability breakage. > >=20 > > I second that. The bindings don't require neither vdd-supply nor > > reset-gpios. > >=20 > > But I have to admit I lack to understand the purpose of this series in = the > > first place. What is the benefit or fix? >=20 > did you followed the provided link from the patch? Ah, I didn't notice that. Thanks. Admittedly I've yet to fully understand t= hat=20 race condition, but Matthias already suspects this series might not be enou= gh,=20 even for boards which do use vdd-supply. Just for the record, this series breaks my board if, as suspected by Doug=20 Anderson and Icenowy Zheng, there is no vdd-supply. The reset line will nev= er=20 be touched. Best regards, Alexander > Best regards >=20 > > Best regards, > > Alexader > >=20 > >> In addition the kernel never fails because of a lacking regulator > >> unless explicitly forbid dummy regulators. > >>=20 > >> BTW USB is a discoverable bus, and if a hub do not need special > >> handlement, it just does not need to appear in the DT, thus no onboard > >> hub DT node. > >>=20 > >>> 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... 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? > >>=20 > >> I agree.