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=-4.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 ECE2EC433E0 for ; Fri, 15 Jan 2021 00:52:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF2AF23AC0 for ; Fri, 15 Jan 2021 00:52:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727301AbhAOAwe (ORCPT ); Thu, 14 Jan 2021 19:52:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbhAOAwd (ORCPT ); Thu, 14 Jan 2021 19:52:33 -0500 Received: from mail-pg1-x52c.google.com (mail-pg1-x52c.google.com [IPv6:2607:f8b0:4864:20::52c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28C48C061575 for ; Thu, 14 Jan 2021 16:51:53 -0800 (PST) Received: by mail-pg1-x52c.google.com with SMTP id n25so4947598pgb.0 for ; Thu, 14 Jan 2021 16:51:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=KsfY+YixsVwmcmnHoOrotECSyW5gjYx8SVQOL2zHmB0=; b=Lu0wfW7aoj2r3PRbDnh+gTDa/E5xSFM7cG7EdFbufvN9yYpCgYXmZNKblSs7172731 sfsfE2Yhok3AoZ61p9p6XosSJ6wIZKTy9sJLAekuNjUrhFGBy8G6X8+mvKL4+8iQXeg1 TuOz1dWkRyGZIPVZPo+lV0XCxMRcpu4X91X/LNE6yc1ssnMjlrbFPbNopml6Ix1guxI7 8JuVjyax6LkD6Ug6bgM+QJJZhDR5cPOKusCAL0yRkvxVeZRsIfzX4CPY/nMrrTmtJ4Gl 69g/rcMa+zrHJcg4UxCpkvtILWLVZNNnvJCfT2EKiEm3Ofv7FxEOw+cKQ81J11q/WuJX Z5JQ== 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:user-agent; bh=KsfY+YixsVwmcmnHoOrotECSyW5gjYx8SVQOL2zHmB0=; b=mazhftFpQ/gdzZUrIYmj5OvgCEQPdIFtSyLCLOa98kjcVx05OQ79SsE99m+jt2lclX xq+y+Q9A+Fhki4AVx2IM22eAFif3SwL4tKVXlv/8ZQkNw16+59EM0Wr1TzTmVGGmIZVz 6qG9Is6hPuLXqa6BJ34vfBNWiZPJ5UJxd2n55gUIK9kXBW+MYk+r/nMHTsN459J2dXe2 OExlRJ0WLQpr35RXrx8zsuAPNHJxT34p5NWbDIeHM5hyb8rd4iO1djx2PADFo3TTE8ks 8l1DGn0jISulXqDB6mHqR2SnAMFtGiw51yB5/AsLCHk7i3uKNx7qdajF04iQcj462S5v P7jw== X-Gm-Message-State: AOAM530dbpD9OSo3yoe0IBf0iMQ3nH2t2GcCM+s1wMAk4rYebLzBwUrG qitqQbojc6OUummN/C778MA= X-Google-Smtp-Source: ABdhPJxJx0Rfcc6SXoekCmDM4fpf89cROKyJoWbDql4p+BbgpBNAluEnhQumtPjjSF+i3oGsDlON2w== X-Received: by 2002:a62:1c16:0:b029:1a6:8b06:68e9 with SMTP id c22-20020a621c160000b02901a68b0668e9mr9891490pfc.45.1610671912675; Thu, 14 Jan 2021 16:51:52 -0800 (PST) Received: from b29397-desktop ([194.5.48.251]) by smtp.gmail.com with ESMTPSA id 22sm6316246pjw.19.2021.01.14.16.51.47 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 14 Jan 2021 16:51:51 -0800 (PST) Date: Fri, 15 Jan 2021 08:51:36 +0800 From: Peter Chen To: Thinh Nguyen Cc: Felipe Balbi , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , John Youn Subject: Re: [PATCH v6 05/11] usb: gadget: composite: Report various SSP sublink speeds Message-ID: <20210115005135.GB3443@b29397-desktop> References: <20210114054708.GB18650@b29397-desktop> <227f3064-8016-33db-6575-fc1a642ef485@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <227f3064-8016-33db-6575-fc1a642ef485@synopsys.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 21-01-14 06:16:18, Thinh Nguyen wrote: > Hi Peter, > > Peter Chen wrote: > > On 21-01-13 18:53:14, Thinh Nguyen wrote: > >> If a gadget supports SuperSpeed Plus, then it may operate in different > >> sublink speeds. For example, if the gadget supports SuperSpeed Plus > >> gen2x2, then it can support 2 sublink speeds gen1 and gen2. Inform the > >> host of these speeds in the BOS descriptor. > >> > > Hi Thinh, > > > > I read USB 3.2 spec: ch9.6.2.5 SuperSpeedPlus USB Device Capability > > > > Symmetric. Rx and Tx Sublinks have the same number of lanes and operate > > at the same speed. > > Asymmetric. Rx and Tx Sublink have different number of lanes and/or > > operate at different speeds. > > > > Why your below cases are all for symmetric, at least, the example 3 > > is asymmetric, it has different speed for sublink pairs? > > Does your below cases are specification defined or user defined? > > USB 3.2 spec section 8.5.6.7: > Asymmetric lane types are only for SuperSpeed Interchip (SSIC). IMO, > It's unlikely that SSIC user will use Linux kernel. We can extend and > update the gadget framework if there's any use case for that. > > > > > >> Use 1 SSID if the gadget supports up to gen2x1, or not specified: > >> - SSID 0 for symmetric RX/TX sublink speed of 10 Gbps. > >> > >> Use 1 SSID if the gadget supports up to gen1x2: > >> - SSID 0 for symmetric RX/TX sublink speed of 5 Gbps. > >> > >> Use 2 SSIDs if the gadget supports up to gen2x2: > >> - SSID 0 for symmetric RX/TX sublink speed of 5 Gbps. > > Why SSID 0 is not 10Gbps? > > SSID 0 and 1 are arbitrary, we can do 0 for 10Gbps. There's no > constraint or standard from the USB 3.2 spec. However, you need to set > the descriptor wFunctionalitySupport.SSID to be the minimum lane speed > SSID it supports. Using SSID 0 makes it easier since we don't have to > condition it for multiple SSIDs. > > >> - SSID 1 for symmetric RX/TX sublink speed of 10 Gbps. > > Besides, would you give me an example what kinds of system design > > will use below sublink speed? > > - SSID 0 for symmetric RX/TX sublink speed of 5 Gbps. > > - SSID 1 for symmetric RX/TX sublink speed of 10 Gbps. > > > > Peter > > These 2 SSIDs indicate that the device is capable of running in gen1 and > gen2 in SSP. > Hi Thinh, I am puzzled, GEN2 is back compatible for GEN1. Then, what's the usage of this descriptor, what kinds of specific information the host wants to get? I think the host wants to get if two pairs of tx/rx are supported, that is what USB 3.2 adds. -- Thanks, Peter Chen