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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F26B3C433F5 for ; Fri, 15 Apr 2022 08:50:11 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8C5881121BE; Fri, 15 Apr 2022 08:50:11 +0000 (UTC) Received: from mail-il1-x129.google.com (mail-il1-x129.google.com [IPv6:2607:f8b0:4864:20::129]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9F30E1121BD for ; Fri, 15 Apr 2022 08:50:10 +0000 (UTC) Received: by mail-il1-x129.google.com with SMTP id e1so4541896ile.2 for ; Fri, 15 Apr 2022 01:50:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=pyHZtUqk/yZ5JeYE4ce1xHZL3ov2K5bIFKslAQ/EBo8=; b=EAsd3Q5pw+uEI/l+mi0URHRfnLw2Nk+ERD/JgJ4iIZlDxVLmaiewwBbPqyatErM5Q6 PC+N9A83F+JML/HKihzczbMlyJryI9kb7VXR1qOnQxuthpGRyYzml8Q/ymoi4DxaL51w WA2d6YhL6DjhgPaBEbcGgMUT8ZQ3ZuPKB54Ey4Z9JzEzEFPorpePHGbEgIMw5Duzk6Cr xSyRGStmg0MLyV5+iLRux70/UnJz4pB2Y176ZwfNYBBOgsf1XV5spIsmzX46zckEsIbb NM6pbUJjt7hXXo3mcdb3lQ7EsmSDka1QBDvJhRf1hz5NqWatv+gKP/qDrpPxWFxUlI93 96Ag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=pyHZtUqk/yZ5JeYE4ce1xHZL3ov2K5bIFKslAQ/EBo8=; b=l78lKPka3KPAmaGpcEQi6ICshHFm+SX7cg4RHtf3bA+SPCEoiHiWw+I7xPoZRBxB3E w3vhPKQhmKaNVAlG+YVK69GHpP4Es0LnvAVxfKJrDyipyzNMAfp7ayx5lYMTwMN2Xnlh tvV8aP4/koEBEimQSpK8HFOl9OqiBMEVtTJAsLNqAzbIlB2Y00BL8vednJqztmB1EWzJ 0UHPbC3PZMO2Am3U11tnTOPj5ecqgWvt0jy2rGx9rpj836rRfCbUo5SquKbLeoay29SA KI0RWl06ZuPI9VK9HCZAHtG6p8s+tP5DhGDCqUyti5VqV6vB9XrSsshdYJSpvyzDqVnU v22g== X-Gm-Message-State: AOAM530sWgtF83mjv8jMaPsfSCzmrENX90gWiy4Php9GukZDYXL7oe+J fclI9IAgsHozTWX/+RQg6X/8SoJJBkJt1KUBhkY+LndK X-Google-Smtp-Source: ABdhPJxTGk1zegqDs3dUL8TGJAG3vPyiW/De8wfwGc2/uERTFYc0K9Ta5akcMJubGplLSbuPcX1iAjHDMNT6luxjRcc= X-Received: by 2002:a05:6e02:1986:b0:2ca:bd0e:a272 with SMTP id g6-20020a056e02198600b002cabd0ea272mr2644090ilf.160.1650012609666; Fri, 15 Apr 2022 01:50:09 -0700 (PDT) MIME-Version: 1.0 References: <28aa9e6b-5267-ea95-9a61-7c488fa97cdc@molgen.mpg.de> In-Reply-To: <28aa9e6b-5267-ea95-9a61-7c488fa97cdc@molgen.mpg.de> From: James Dutton Date: Fri, 15 Apr 2022 09:49:33 +0100 Message-ID: Subject: Re: Vega 56 failing to process EDID from VR Headset To: Paul Menzel Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: amd-gfx@lists.freedesktop.org Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On Wed, 13 Apr 2022 at 08:11, Paul Menzel wrote: > > Dear James, > > > I will do some more investigation. In addition to it not processing > > the EDID particularly well... > > Since my email, I have found out that it is failing to complete CR > > (Clock Recovery) on Link 0,2, but it works on 1,3 at HBR2. All 4 Links > > work at HBR1. (I need the HBR2 working) > > The CR negotiation in the code looks a bit wrong to me, so I will look > > into that a bit more. > > Looking at the current amdgpu source code (I am using Mainline > > kernel version 5.17.1), it appears to retry CR negotiation, but each > > time it uses the same settings, rather than try different driver > > parameters, as recommended in the DP standards and compliance test > > documents. > > [=E2=80=A6] > > Awesome, that you review the code with your expertise. Though I suggest > to look at and work on agd5f/amd-staging-drm-next [1], having the latest > code for the driver. > Just a small update. I have CR negotiation working now. I have found out what I suspected. Although the amdgpu driver has code in it that looks like CR negotiation is implemented, it does not actually do any negotiation at all. I still have some work to do, to also get EQ negotiation working. Once I have a patch that is tidy enough, I will raise a bug request and attach the patch to it. I am just pleased that this is a software problem, and not my screen at fau= lt. Someone mentioned that the amdgpu driver is DP compliance tested periodically. In short, I don't think any of those Link negotiation DP compliance tests are actually valid, based on what I have found, so it might be sensible for the person who runs the Link negotiation DP compliance test suite to double check it is actually doing its job. Summary: During CR negotiation, it only ever outputs a swing of 0, and never 1,2 or 3 as it should. So, my guess is only Screens on relatively short cables have ever worked with the Linux amdgpu driver. Although longer cables might work for some, it probably gets a bit hit and miss for them. Kind Regards James