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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 8BA8AC4320A for ; Wed, 4 Aug 2021 23:38:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 59829610CD for ; Wed, 4 Aug 2021 23:38:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233915AbhHDXjG (ORCPT ); Wed, 4 Aug 2021 19:39:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:47136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233775AbhHDXjF (ORCPT ); Wed, 4 Aug 2021 19:39:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0AE9E61037; Wed, 4 Aug 2021 23:38:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628120332; bh=h/WL88N/qB73Qu9R4aafhExy3Rm8W7zuv5+DwEs6Q6w=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=aawEBKA984kKtwMG0dlt1H+VrEfyO1QfSF/BstIe7KJfDVvu1++EWRhk/LrqJQyQy bcRjkKeQsVUxPqyH9taGZAd7N7YHO0uxPqpuwlN1yzc12Xirt7syIYddkmUI2m+E+C yMB8BWkQIKdAYwTqo8hkoDIHZbQTTZZzAFo8CR7M8NwD8EkENg4796D7e/X+DzjhUz TZYpRL2uUl9YmugtVrVpgai0bd23iLqcUetARle6jPiP8POWa7V11kAIdbisjHu7WL k0BWMgXF/crVZpJ4+MnQ5l6p80n+PCDlE942x2wfKYsikhg1LqT6RzOiQw5eqbeV2t x6Wwdz6BHLpEQ== Date: Wed, 4 Aug 2021 18:38:50 -0500 From: Bjorn Helgaas To: Dongdong Liu Cc: hch@infradead.org, kw@linux.com, logang@deltatee.com, leon@kernel.org, linux-pci@vger.kernel.org, rajur@chelsio.com, hverkuil-cisco@xs4all.nl, linux-media@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH V7 6/9] PCI: Enable 10-Bit Tag support for PCIe RP devices Message-ID: <20210804233850.GA1691988@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1628084828-119542-7-git-send-email-liudongdong3@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Wed, Aug 04, 2021 at 09:47:05PM +0800, Dongdong Liu wrote: > PCIe spec 5.0r1.0 section 2.2.6.2 implementation note, In configurations > where a Requester with 10-Bit Tag Requester capability needs to target > multiple Completers, one needs to ensure that the Requester sends 10-Bit > Tag Requests only to Completers that have 10-Bit Tag Completer capability. > So we enable 10-Bit Tag Requester for root port only when the devices > under the root port support 10-Bit Tag Completer. Fix quoting. I can't tell what is from the spec and what you wrote. > Signed-off-by: Dongdong Liu > --- > drivers/pci/pcie/portdrv_pci.c | 69 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c > index c7ff1ee..2382cd2 100644 > --- a/drivers/pci/pcie/portdrv_pci.c > +++ b/drivers/pci/pcie/portdrv_pci.c > @@ -90,6 +90,72 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = { > #define PCIE_PORTDRV_PM_OPS NULL > #endif /* !PM */ > > +static int pci_10bit_tag_comp_support(struct pci_dev *dev, void *data) > +{ > + bool *support = (bool *)data; > + > + if (!pci_is_pcie(dev)) { > + *support = false; > + return 1; > + } > + > + /* > + * PCIe spec 5.0r1.0 section 2.2.6.2 implementation note. > + * For configurations where a Requester with 10-Bit Tag Requester > + * capability targets Completers where some do and some do not have > + * 10-Bit Tag Completer capability, how the Requester determines which > + * NPRs include 10-Bit Tags is outside the scope of this specification. > + * So we do not consider hotplug scenario. > + */ > + if (dev->is_hotplug_bridge) { > + *support = false; > + return 1; > + } > + > + if (!(dev->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP)) { > + *support = false; > + return 1; > + } > + > + return 0; > +} > + > +static void pci_configure_rp_10bit_tag(struct pci_dev *dev) > +{ > + bool support = true; > + > + if (dev->subordinate == NULL) > + return; > + > + /* If no devices under the root port, no need to enable 10-Bit Tag. */ > + if (list_empty(&dev->subordinate->devices)) > + return; > + > + pci_10bit_tag_comp_support(dev, &support); > + if (!support) > + return; > + > + /* > + * PCIe spec 5.0r1.0 section 2.2.6.2 implementation note. > + * In configurations where a Requester with 10-Bit Tag Requester > + * capability needs to target multiple Completers, one needs to ensure > + * that the Requester sends 10-Bit Tag Requests only to Completers > + * that have 10-Bit Tag Completer capability. So we enable 10-Bit Tag > + * Requester for root port only when the devices under the root port > + * support 10-Bit Tag Completer. > + */ > + pci_walk_bus(dev->subordinate, pci_10bit_tag_comp_support, &support); > + if (!support) > + return; > + > + if (!(dev->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_REQ)) > + return; > + > + pci_dbg(dev, "enabling 10-Bit Tag Requester\n"); > + pcie_capability_set_word(dev, PCI_EXP_DEVCTL2, > + PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); > +} > + > /* > * pcie_portdrv_probe - Probe PCI-Express port devices > * @dev: PCI-Express port device being probed > @@ -111,6 +177,9 @@ static int pcie_portdrv_probe(struct pci_dev *dev, > (type != PCI_EXP_TYPE_RC_EC))) > return -ENODEV; > > + if (type == PCI_EXP_TYPE_ROOT_PORT) > + pci_configure_rp_10bit_tag(dev); I don't think this has anything to do with the portdrv, so all this should go somewhere else. Out of curiosity, IIUC this enables 10-bit tags for MMIO transactions from the root port toward the device, i.e., traffic that originates from a CPU. Is that a significant benefit? I would expect high-speed devices would primarily operate via DMA with relatively little MMIO traffic. > if (type == PCI_EXP_TYPE_RC_EC) > pcie_link_rcec(dev); > > -- > 2.7.4 >