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=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 3476AC433B4 for ; Tue, 6 Apr 2021 18:01:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4EC2613D8 for ; Tue, 6 Apr 2021 18:01:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236445AbhDFSBt (ORCPT ); Tue, 6 Apr 2021 14:01:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234333AbhDFSBs (ORCPT ); Tue, 6 Apr 2021 14:01:48 -0400 Received: from mail-ua1-x92a.google.com (mail-ua1-x92a.google.com [IPv6:2607:f8b0:4864:20::92a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72600C06174A for ; Tue, 6 Apr 2021 11:01:40 -0700 (PDT) Received: by mail-ua1-x92a.google.com with SMTP id s2so654853uap.1 for ; Tue, 06 Apr 2021 11:01:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=nbgL2Qq4BnarnUuwkqdsPhJlo1aRh+4yOXd+IwjHg+o=; b=Tsy8czEEzk6mVMWek893ZuICWwWNznqaOeneAGUu0Xy0w6oRImpv3CyYSo1dq66qfG BHHkJfB0K7VklqQUEWYa+yBwbX1q1wnuT4VwcQw7PyeaGcX44V9e8Z/wNwGNcP5NDCiG ij9mol6gRQEWCJ+LQvCCjqESbmstqwXnS5+Ko= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=nbgL2Qq4BnarnUuwkqdsPhJlo1aRh+4yOXd+IwjHg+o=; b=JWtJ7HB1w+uOvtZTA/eZtoGtt9XVb1DoyM2flszXwbEU7DPdOLkyuKqWK8lpzEcTQz tnrY3O7xusEERVC4hifJWjPCSwvfDMHYTDaDZI+uhdUAwkorGv/aPesZCXyo67d0fr/k Ls9Be0p2N9udvqEpsiymk6acjuDgbkl6fanb8lBZ9VYSbyyYllD8OkHcGml4r1/0cW1f vSdE9wsPhnt9bBv1QjmkwgCcGusr+PU94I2V9lFG0MgEsAGfGlpzOTrbbpRVkK6ApCCh FMwoFPh+zelE4HZBlLeuug4vW1FGPdy8i6S/Vblh/0UoPuqi1SDgscS5Pc/zdNmrV31M 1wlw== X-Gm-Message-State: AOAM530cERLNIf6PTLfUSUJjg7rPqoUk2phf1RBy4zQqXHepHIE6ee7V e0LpaRMhi5by1JFoNlSlvhqvkVLDfHv/eyR9TOhEtg== X-Google-Smtp-Source: ABdhPJxIBX8FPIcavna8dpkkkJzqxvRkitCszIZiZaoDO1jByymqs+zNZyMuzPZKO/wRuv3V5UH7u+KPe8SbGetujrQ= X-Received: by 2002:ab0:3885:: with SMTP id z5mr4476593uav.84.1617732099269; Tue, 06 Apr 2021 11:01:39 -0700 (PDT) MIME-Version: 1.0 References: <20210405231344.1403025-1-grundler@chromium.org> In-Reply-To: From: Grant Grundler Date: Tue, 6 Apr 2021 18:01:27 +0000 Message-ID: Subject: Re: [PATCH net-next v4 0/4] usbnet: speed reporting for devices without MDIO To: Andrew Lunn Cc: Grant Grundler , Oliver Neukum , Jakub Kicinski , Roland Dreier , nic_swsd , netdev , "David S . Miller" , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Key part of Andew's reply: "Yes, this discussion should not prevent this patchset from being merged."] On Tue, Apr 6, 2021 at 1:00 PM Andrew Lunn wrote: > > > > Speed: 2500Mb/s and Duplex: Half is very unlikely. You really only > > > ever see 10 Half and occasionally 100 Half. Anything above that will > > > be full duplex. > > > > > > It is probably best to admit the truth and use DUPLEX_UNKNOWN. > > > > Agreed. I didn't notice this "lie" until I was writing the commit > > message and wasn't sure off-hand how to fix it. Decided a follow on > > patch could fix it up once this series lands. > > > > You are right that DUPLEX_UNKNOWN is the safest (and usually correct) default. > > Additionally, if RX and TX speed are equal, I am willing to assume > > this is DUPLEX_FULL. > > Is this same interface used by WiFi? I doubt WiFi could work with this driver interface (though maybe with "SendEncapsulatedCommand"). All the Wifi Devices I'm familiar with need WPA support and communicate through 80211 kernel subsystem. I was thinking of just about everything else: Cellular modem (cdc_ether), xDSL, or other broadband. > Ethernet does not support > different rates in each direction. So if RX and TX are different, i > would actually say something is broken. Agreed. The question is: Is there data or some heuristics we can use to determine if the physical layer/link is ethernet? I'm pessimistic we will be able to since this is at odds with the intent of the CDC spec. > 10 Half is still doing 10Mbps > in each direction, it just cannot do both at the same time. > WiFi can have asymmetric speeds. *nod* > > I can propose something like this in a patch: > > > > grundler <1637>git diff > > diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c > > index 86eb1d107433..a7ad9a0fb6ae 100644 > > --- a/drivers/net/usb/usbnet.c > > +++ b/drivers/net/usb/usbnet.c > > @@ -978,6 +978,11 @@ int usbnet_get_link_ksettings_internal(struct > > net_device *net, > > else > > cmd->base.speed = SPEED_UNKNOWN; > > > > + if (dev->rx_speed == dev->tx_speed) > > + cmd->base.duplex = DUPLEX_FULL; > > + else > > + cmd->base.duplex =DUPLEX_UNKNOWN; > > + > > return 0; > > } > > EXPORT_SYMBOL_GPL(usbnet_get_link_ksettings_internal); > > So i would say this is wrong. I would just set DUPLEX_UNKNOWN and be > done. Ok. > > I can send this out later once this series lands or you are welcome to > > post this with additional checks if you like. > > Yes, this discussion should not prevent this patchset from being > merged. Good. That's what I'm hoping for. > > If we want to assume autoneg is always on (regardless of which type of > > media cdc_ncm/cdc_ether are talking to), we could set both supported > > and advertising to AUTO and lp_advertising to UNKNOWN. > > I pretty much agree autoneg has to be on. If it is not, and it is > using a forced speed, there would need to be an additional API to set > what it is forced to. There could be such proprietary calls, but the > generic cdc_ncm/cdc_ether won't support them. Good observation. Agreed. > But i also don't know how setting autoneg actually helps the user. Just to let them know the link rate can change and is dynamically determined. > Everybody just assumes it is supported. If you really know auto-neg is > not supported and you can reliably indicate that autoneg is not > supported, that would be useful. But i expect most users want to know > if their USB 2.0 device is just doing 100Mbps, or if their USB 3.0 > device can do 2.5G. For that, you need to see what is actually > supported. Yes. Other than using a table to look up USB VID:PID, I don't see anything in the spec which provides "media-specific" information. I was curious about the "can do 2.5Gbps?" question by looking at the CDC Ethernet Networking Functional Descriptor (USBECM12) and other CDC specs. The spec feels like a "compatibility wrapper" to make a cellular modem look like an ethernet device. This statement in the ECM120.pdf I have suggests we can not determine media layer: The effect of a "reset" on the device physical layer is media-dependent and beyond the scope of this specification. cheers, grant