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 30193C433FE for ; Sat, 1 Oct 2022 23:50:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229544AbiJAXuY (ORCPT ); Sat, 1 Oct 2022 19:50:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229540AbiJAXuV (ORCPT ); Sat, 1 Oct 2022 19:50:21 -0400 Received: from out1.migadu.com (out1.migadu.com [IPv6:2001:41d0:2:863f::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C4A420BDE; Sat, 1 Oct 2022 16:50:15 -0700 (PDT) Message-ID: <2a465222-342a-418b-95af-9948f6ce9065@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1664668213; 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=E50mveDkhjyT/f41Fre/RrdiU0a3ioACNtlJoHsW0io=; b=ONPbNZ3JwSONx6g62DdPSiaRq5lycwAkGySS5As9hNZwrdh2m4KHrSq3euYqmO9EW8zNbi hw9SuxjfSn5rBmkbKy7YwFly/6WlOJE1Ut6HqMSygMYoMUInZ/h0oh674Zhc3VF6r5NANt cXqkxZESbjiIi1HilBDEmxQfGXJEvxo= Date: Sat, 1 Oct 2022 17:50:07 -0600 MIME-Version: 1.0 Subject: Re: [PATCH V1 0/4] GPIO based PCIe Hot-Plug support To: =?UTF-8?Q?Pali_Roh=c3=a1r?= , Lukas Wunner Cc: Vidya Sagar , bhelgaas@google.com, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, lpieralisi@kernel.org, kw@linux.com, thierry.reding@gmail.com, jonathanh@nvidia.com, mani@kernel.org, Sergey.Semin@baikalelectronics.ru, jszhang@kernel.org, linux-pci@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com, =?UTF-8?Q?Marek_Beh=c3=ban?= References: <20220930192747.21471-1-vidyas@nvidia.com> <20221001160025.GB9324@wunner.de> <20221001162049.ln2qheyyb5muifi7@pali> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Jonathan Derrick In-Reply-To: <20221001162049.ln2qheyyb5muifi7@pali> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On 10/1/2022 10:20 AM, Pali Rohár wrote: > On Saturday 01 October 2022 18:00:25 Lukas Wunner wrote: >> Adding Marek, Pali & Jon to cc as they've worked on somewhat similar >> functionality: >> >> https://lore.kernel.org/linux-pci/20220927141926.8895-1-kabel@kernel.org/ >> https://lore.kernel.org/linux-pci/1581120007-5280-1-git-send-email-jonathan.derrick@intel.com/ >> >> On Sat, Oct 01, 2022 at 12:57:43AM +0530, Vidya Sagar wrote: >>> To support the Hot-plug feature, PCIe spec has a well-defined model for >>> hardware implementation and software programming interface. There are also >>> some architectures/platforms where the Hot-plug feature is implemented in a >>> non-standard way and software support for the respective implementations is >>> available with the kernel. This patch series attempts to add support for one >>> such non-standard way of supporting the Hot-plug feature where a single GPIO >>> is used to detect and report the Hot-Plug and Unplug events to the SW. >>> The platforms that can use this piece of software need to have GPIO routed >>> from the slot to the controller which can indicate the presence/absence of >>> the downstream device through its state. This GPIO should also have the >>> capability to interrupt the system when the connection/disconnection event >>> takes place. >>> A GPIO Hot-plug framework is written which looks for a "hotplug-gpios" named >>> GPIO entry in the corresponding device-tree entry of the controller and >>> registers a hot-pluggable slot with the Hot-plug framework. >>> The platform drivers of the PCIe host bridges/root ports can register with the >>> aforementioned GPIO Hot-Plug framework along with ops to perform any platform >>> specific tasks during Hot-Plug/Unplug events. >>> >>> Oza Pawandeep made an attempt to upstream support for a similar Hot-plug >>> feature implementation at a platform level, but the implementation as such >>> was very specific to that platform (at least the way I understood it). >>> https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-2-git-send-email-oza.oza@broadcom.com/ >>> https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-3-git-send-email-oza.oza@broadcom.com/ >>> https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-4-git-send-email-oza.oza@broadcom.com/ >>> This current series also attempts to address that by extracting out all the >>> common code to do with GPIO and Hot-plug core framework and expecting the >>> platform drivers to only register/unregister with the GPIO framework. So, >>> @Oza, could you try using the GPIO framework from this series and enable >>> Hot-plug support for your platform if it still makes sense? > > Hello! > > Would not it better to rather synthesise PCIe Slot Capabilities support > in your PCIe Root Port device (e.g. via pci-bridge-emul.c) and then let > existing PCI hotplug code to take care for hotplugging? Because it > already implements all required stuff for re-scanning, registering and > unregistering PCIe devices for Root Ports with Slot Capabilities. And I > think that there is no need to have just another (GPIO based) > implementation of PCI hotplug. I did that a few years ago (rejected), but can attest to the robustness of the pcie hotplug code on non-hotplug slots. https://lwn.net/Articles/811988/ > > Similar thing Marek and me have implemented for PCIe link state events > in patch series with Lukas pointed. > >>> @Rob, >>> Regarding the DT documentation change to add about 'hotplug-gpios, I'm not >>> sure if pci.txt is the right place or the dt-schema repository >>> i.e https://github.com/devicetree-org/dt-schema >>> But, in the interest of keeping all the changes related to this feature in the >>> the same repository, I made the changes to the pci.txt file in this repo itself. >>> Please let me know if the documentation change needs to be moved to the other >>> repo. >>> >>> The Changes have been tested on the Tegra234 platform. >>> >>> Vidya Sagar (4): >>> dt-bindings: Add "hotplug-gpios" PCIe property >>> PCI/hotplug: Add GPIO PCIe hotplug driver >>> PCI: tegra194: Add support to configure a pluggable slot >>> PCI: tegra194: Enable GPIO based Hot-Plug support >>> >>> Documentation/devicetree/bindings/pci/pci.txt | 4 + >>> drivers/pci/controller/dwc/pcie-tegra194.c | 85 +++++++- >>> drivers/pci/hotplug/Kconfig | 11 + >>> drivers/pci/hotplug/Makefile | 1 + >>> drivers/pci/hotplug/gpio_php.c | 200 ++++++++++++++++++ >>> drivers/pci/hotplug/gpiophp.h | 40 ++++ >>> 6 files changed, 334 insertions(+), 7 deletions(-) >>> create mode 100644 drivers/pci/hotplug/gpio_php.c >>> create mode 100644 drivers/pci/hotplug/gpiophp.h >>> >>> -- >>> 2.17.1 >>>