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=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 D5D45C433F5 for ; Thu, 9 Sep 2021 15:39:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACBB561101 for ; Thu, 9 Sep 2021 15:39:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232029AbhIIPk0 (ORCPT ); Thu, 9 Sep 2021 11:40:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:53778 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229745AbhIIPkZ (ORCPT ); Thu, 9 Sep 2021 11:40:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631201956; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NAoGWGPtsnAq49mA/RMrMqfbYA/9DWb9jHUJdmT/k/o=; b=iO4nuWvrGN4ugOvW76OrfLkrNiAC0RsrIRaSAEwSoret1hYpujsZVgrYEkfmW72Uf6rwz2 4vJnBi4gFcAAEr3xHdI/ZFt0La/9s17yftv/yfw5L/GFV6wHcxNUqIAueYcemqYrUZ4YJd ZuQcI8732ILSzgQjHxDtJnRA7TLxL9w= Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-469-vbQ6EMJkOpaBWStlrCaxjA-1; Thu, 09 Sep 2021 11:39:14 -0400 X-MC-Unique: vbQ6EMJkOpaBWStlrCaxjA-1 Received: by mail-oi1-f198.google.com with SMTP id u23-20020acaab17000000b0026857819b52so1261574oie.1 for ; Thu, 09 Sep 2021 08:39:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=NAoGWGPtsnAq49mA/RMrMqfbYA/9DWb9jHUJdmT/k/o=; b=V31VdISVQR3M44QIfmGQHFWGpLLc1ZRuYWYYhiXfZ7TfuvGHw9xJptCAVeFHFlXbnV X3fhc2Ob5B6C8kE+m7wCp31yeN1McshlGNXsV/dgkvrCbUNjwFatWqMbsVwDPDfrU/FB 2iR5X7zk+c1wGPEPzqw0ZgKIja8s99ucd7HrVxjvHl6W8fuTAJW4leZbO0oPv0ex6P7L hiyX6GviLU9pStwsVAMA/zHmhZsaWoJ3Lu7cpnP6WKBFjBAbfL+VVFZJCOyi6XTniJpH uXbnVocAjPg6+/EJFdBcuSRz+Zcm4hY9eX+qMTNqRjDbRXCgc8okaxWmoIz3fa1kCcmF SM3g== X-Gm-Message-State: AOAM530Wq3PcxJOgzbFQVSeeYjkoXPUgNoLQQCpDMagE2Q3MA376n/ID +U+Fr0EQuq+l4zSrAcfAHm7h6mp4nmqJtSP3gSavXCDvifwtTKcIrlCySmBOzkOA77mhKUnlDdc Tyfjz3aVmLYHfPEDxmwZR X-Received: by 2002:a9d:630e:: with SMTP id q14mr418227otk.316.1631201954139; Thu, 09 Sep 2021 08:39:14 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzzzncNWg2v091gvZjadEV35dq8or54nXg1XSQmDjzvuWHq6fncTlgpM5zdL7kC5EKXQ+OwDw== X-Received: by 2002:a9d:630e:: with SMTP id q14mr418142otk.316.1631201953085; Thu, 09 Sep 2021 08:39:13 -0700 (PDT) Received: from redhat.com ([198.99.80.109]) by smtp.gmail.com with ESMTPSA id a1sm525600otr.33.2021.09.09.08.39.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Sep 2021 08:39:12 -0700 (PDT) Date: Thu, 9 Sep 2021 09:39:11 -0600 From: Alex Williamson To: Nathan Rossi Cc: linux-pci@vger.kernel.org, Nathan Rossi , Lukas Wunner , Bjorn Helgaas Subject: Re: [PATCH v2] PCI: Add ACS errata for Pericom PI7C9X2G404 switch Message-ID: <20210909093911.03952664.alex.williamson@redhat.com> In-Reply-To: <20210909080927.164709-1-nathan@nathanrossi.com> References: <20210909080927.164709-1-nathan@nathanrossi.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, 09 Sep 2021 08:09:27 +0000 Nathan Rossi wrote: > From: Nathan Rossi > > The Pericom PI7C9X2G404 PCIe switch has an errata for ACS P2P Request > Redirect behaviour when used in the cut-through forwarding mode. The > recommended work around for this issue is to use the switch in store and > forward mode. The errata results in packets being queued and not being > delivered upstream, this can be observed as very poor downstream device > performance and/or dropped device generated data/interrupts. > > This change adds a fixup specific to this switch that when enabling or > resuming the downstream port it checks if it has enabled ACS P2P Request > Redirect, and if so changes the device (via the upstream port) to use > the store and forward operating mode. > > Signed-off-by: Nathan Rossi Thanks for pursuing this! I took a stab at it[1] some time ago but I tried to pursue link balancing, I didn't have the datasheet to realize we could simply put the device in a different mode and blindly assumed the mode was inherit to the unbalanced link config. Link balancing turned out to be more complicated than I cared or had time to pursue. Also related to this device, there is a kernel bz for this issue that might provide more details[2], Bjorn will probably want to add that reference to the commit log. I'll see if I can find the card from that bz to test here. Thanks, Alex [1]https://lore.kernel.org/all/20161026175156.23495.12980.stgit@gimli.home/ [2]https://bugzilla.kernel.org/show_bug.cgi?id=177471 > --- > Changes in v2: > - Added DECLARE_PCI_FIXUP_RESUME to handle applying fixup upon resume as > switch operation may have been reset or ACS configuration may have > changed > --- > drivers/pci/quirks.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 48 insertions(+) > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index e5089af8ad..5849b7046b 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -5790,3 +5790,51 @@ static void apex_pci_fixup_class(struct pci_dev *pdev) > } > DECLARE_PCI_FIXUP_CLASS_HEADER(0x1ac1, 0x089a, > PCI_CLASS_NOT_DEFINED, 8, apex_pci_fixup_class); > + > +/* > + * Pericom PI7C9X2G404 switch errata E5 - ACS P2P Request Redirect is not > + * functional > + * > + * When ACS P2P Request Redirect is enabled and bandwidth is not balanced > + * between upstream and downstream ports, packets are queued in an internal > + * buffer until CPLD packet. The workaround is to use the switch in store and > + * forward mode. > + */ > +#define PI7C9X2G404_MODE_REG 0x74 > +#define PI7C9X2G404_STORE_FORWARD_MODE BIT(0) > +static void pci_fixup_pericom_acs_store_forward(struct pci_dev *pdev) > +{ > + struct pci_dev *upstream; > + u16 val; > + > + /* Downstream ports only */ > + if (pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM) > + return; > + > + /* Check for ACS P2P Request Redirect use */ > + if (!pdev->acs_cap) > + return; > + pci_read_config_word(pdev, pdev->acs_cap + PCI_ACS_CTRL, &val); > + if (!(val & PCI_ACS_RR)) > + return; > + > + upstream = pci_upstream_bridge(pdev); > + if (!upstream) > + return; > + > + pci_read_config_word(upstream, PI7C9X2G404_MODE_REG, &val); > + if (!(val & PI7C9X2G404_STORE_FORWARD_MODE)) { > + pci_info(upstream, "Setting PI7C9X2G404 store-forward mode\n"); > + /* Enable store-foward mode */ > + pci_write_config_word(upstream, PI7C9X2G404_MODE_REG, val | > + PI7C9X2G404_STORE_FORWARD_MODE); > + } > +} > +/* > + * Apply fixup on enable and on resume, in order to apply the fix up whenever > + * ACS configuration changes or switch mode is reset > + */ > +DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_PERICOM, 0x2404, > + pci_fixup_pericom_acs_store_forward); > +DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_PERICOM, 0x2404, > + pci_fixup_pericom_acs_store_forward); > --- > 2.33.0 >