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 D9B96C433F5 for ; Tue, 25 Jan 2022 14:05:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385761AbiAYOFL (ORCPT ); Tue, 25 Jan 2022 09:05:11 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:10054 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244466AbiAYOCA (ORCPT ); Tue, 25 Jan 2022 09:02:00 -0500 Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 20PDa1B1026888; Tue, 25 Jan 2022 14:01:41 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : references : date : in-reply-to : message-id : mime-version : content-type; s=pp1; bh=hM+U2dlqP46OUo4fwxEPEJfGWMF4re/nYmzSS2JOeRc=; b=hZCiJ2CAWduSzQpBnyHIC33rqkEsePodhpbctvVzBHdarFOvdKVcjQ25zxq+UuskPeYX cP/LFODS+jLGf8G7mQvfJCjjM1OdRQs4b0e11EU7kRIb+gCSg6OsUVfR2N8RlVKG3d2y P2gR/7qPM9zRqc6bChkHBf90Ujawqt3Gtqi0b/ykT1JIVLXOQTl2Q1l4dohHYN8bzBSB YypXC+oaCk+KKRjYU1SQxF253PlFOL9lgIig7Tvze5Opln/ZYwMfjENF9OF9ZwtXTuSt Q3JY+cObvrKsaYnIFVyHbXZnmBwNqcurivUyT5HqMI6n5AHbyFMltFWTY+evXnORzAHp FA== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com with ESMTP id 3dthxvrvuy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 25 Jan 2022 14:01:41 +0000 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 20PDwLK9020971; Tue, 25 Jan 2022 14:01:39 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma06ams.nl.ibm.com with ESMTP id 3dr96jetbv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 25 Jan 2022 14:01:39 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 20PE1aLX42860816 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Jan 2022 14:01:37 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D0E7742047; Tue, 25 Jan 2022 14:01:36 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 930654204B; Tue, 25 Jan 2022 14:01:36 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.152.85.9]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 25 Jan 2022 14:01:36 +0000 (GMT) From: Sven Schnelle To: Peter Zijlstra Cc: Mathias Nyman , Greg KH , Dave Hansen , Lu Baolu , x86@kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Chunfeng Yun Subject: Re: earlyprintk=xdbc seems broken References: Date: Tue, 25 Jan 2022 15:01:36 +0100 In-Reply-To: (Peter Zijlstra's message of "Tue, 25 Jan 2022 14:54:01 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-GUID: iYUsxqAKHKiGZOdJeA37eLFAyGmJX0Zv X-Proofpoint-ORIG-GUID: iYUsxqAKHKiGZOdJeA37eLFAyGmJX0Zv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-25_02,2022-01-25_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 mlxscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 spamscore=0 priorityscore=1501 clxscore=1015 suspectscore=0 impostorscore=0 mlxlogscore=765 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2201250092 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Tue, Jan 25, 2022 at 02:09:18PM +0100, Sven Schnelle wrote: >> Peter Zijlstra writes: >> >> > Now the documentation states we need this super speed A<->A cable, but >> > could you also update the documentation for usb-c ? There's a fair >> > number of usb-c only devices out there now. >> >> Stupid beginners question: Would every USB3 A-A cable work, or are the >> debug cables special? I've read the RX/TX pairs have to be swapped, but >> to me it looks like that's always the case? > > I'm using a random USB3 A-A cable (it came with an HDMI frame grabber of > of AliExpress). The official one has a wire missing I think, to avoid > ground loops or something like that. > > The easiest thing to do is try the runtime DBC option: > > echo enable > /sys/bus/pci/devices/0000:00:14.0/dbc > > If that works you can see what it takes to make the earlyprintk one > working. This thread seems to have much of that covered. Thanks, the sysfs test works for me. I have two A-A cables, one is from a cheap PCI-e extender, the other one from a KVM switch. Both work, which is great. So i assume that most A-A cable would work. I'm building a new kernel now with the patch on top, lets see. Thanks!