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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 0ED0AC433ED for ; Thu, 22 Apr 2021 11:15:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C42616145E for ; Thu, 22 Apr 2021 11:15:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236085AbhDVLQ2 (ORCPT ); Thu, 22 Apr 2021 07:16:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:38230 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236074AbhDVLQ1 (ORCPT ); Thu, 22 Apr 2021 07:16:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 99AAC6145A; Thu, 22 Apr 2021 11:15:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619090153; bh=UAqK6UxxZFJ5XZ3GXSc1DWfVYEAyRQz+4ooT09o1oN0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Cf1lCsp8V2I/KXotHAitazs36hNXcxSIUIToEefTlPGCfcvTsMgZy09oZzSJ4Xvsh VPKQDHbZf3F14iGCTlq9sCDL4WsyEHNJCnmJCXsK0V8LWGF6GuOwtJnDd1BgdFbyfh uChSlt/rfR+B4dDGUCxYERRAEqU6P3txWgfE9Hc8= Date: Thu, 22 Apr 2021 13:15:50 +0200 From: Greg KH To: Roman Mamedov Cc: linux-usb@vger.kernel.org Subject: Re: Not enough bandwidth for new device state -- with Etron USB3 controller only Message-ID: References: <20210421223732.27080321@natsu> <20210422160813.41e26426@natsu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210422160813.41e26426@natsu> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Apr 22, 2021 at 04:08:13PM +0500, Roman Mamedov wrote: > Hello, > > On Thu, 22 Apr 2021 07:49:38 +0200 > Greg KH wrote: > > > Not a bug, this is how USB works. Your first hub really does not have > > enough bandwidth for that device. Well, we think it doesn't, the > > calculation for that is really really tricky and we error on the side of > > "let's not take the risk and just disable the device to be safe". > > > > Get a better hub :) > > But why the calculation is different when the hub is plugged into the onboard > USB 2.0 controller -- and there it works? You have more hubs in the way, they take up bandwidth on their own just sitting there. > I hope you don't take this as a bug report to make it stop working there as > well. :) > > If it's because the Etron controller is USB 3.0, and the higher speeds are > somehow accounted for in the bandwidth calculation, that doesn't seem right, > since both of the plugged in downstream hubs are 1.1/2.0-only. USB 2 hubs plugged into a USB 3 controller require horrible things to be done on the wire to make everything work properly. Part of that horribleness is bandwidth determination that we honestly are not the best at in Linux. But again, we err on the side of safety, which means we guess on the low-end compared to other operating systems. thanks, greg k-h