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 9B5F9C38142 for ; Tue, 24 Jan 2023 07:16:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233485AbjAXHQT (ORCPT ); Tue, 24 Jan 2023 02:16:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233477AbjAXHQN (ORCPT ); Tue, 24 Jan 2023 02:16:13 -0500 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2D003AA6 for ; Mon, 23 Jan 2023 23:16:11 -0800 (PST) Received: by mail-pj1-x1033.google.com with SMTP id j5so294846pjn.5 for ; Mon, 23 Jan 2023 23:16:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=SiurnOYAkeKt29fHrAzebFb+oWYWVydRMZlV3KhJgps=; b=FIEUh4JxydUOaCsXsiTa4mg/Yx4/E35uzA6fUk4BLH+osNOAqiLKTI+Bh7khgxLGpz LiyB/RxEwe1voPsIZsn2Jm54v/4OK/Q3980vm1SHgI3Rv0LL2A7zKDpvLGg+te33hZAm L6JkFomSbbmFmYeE+wgXyadq7dx8GgWj0hDYmBJORKpSQNgVWm1IHKfiaccGdYvMEp02 wFqM4axXMSoll1urC1zBGQufqGIqTdrRtHp475dwAOapcVSjosLIRS10c8fYLWXodpvD X5IGvHGiyu75LneBXq2ASRWA3bhQPwtvwguDw/tyulIl1ti+6rwGsxcbg5VxVhdClxxJ dNcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=SiurnOYAkeKt29fHrAzebFb+oWYWVydRMZlV3KhJgps=; b=e0PRqrw1X2Nx2PRc9aPlJ8V8gSnGYeW3FnAxq/KSnPbnGyUSPZ0au8JlyNPqNTHvCf mG7nJcWhntumQOyWdKD5c788j8SU1tPFAmrvEw50Ren3kpaypJMJftyKVbOW3uSZxgml lQJ/8LgUWkRiGkHDEArBhsxvLDfOzBcg4pnQ0u6oNo7oYEOrKbaJCxNxPWyCy+VN1B72 Adcr3HlIT6FkwwETeD1yPJsoYA0aWYI+hByVzMayFtnkf1CgWYLSgSAvOEoDiu8vPcao wIWJv8VlCX5A9bOXlb3jOINnTpFo47zvPe5dNIURysUZ0e1+OZqkaK8Hy2vJ1FwpCJrr LMSQ== X-Gm-Message-State: AFqh2kqyqKg44vdEI52e10MRh+9yGEEkcezntOJ7ZFN4swQr1vy6zjFC ST0dU0mBpOWHCl4nbg78dJybnZy9mlvFgOA= X-Google-Smtp-Source: AMrXdXu4mi6dvGvEO/n/C5xxXN1FLj9XQ2O0zlWnVWpPCjshvxCfAR8WoMfy5X7ZEJve9bf9pc0YkQ== X-Received: by 2002:a05:6a20:be03:b0:b8:5813:e700 with SMTP id ge3-20020a056a20be0300b000b85813e700mr37929542pzb.3.1674544571225; Mon, 23 Jan 2023 23:16:11 -0800 (PST) Received: from thinkpad ([117.193.209.165]) by smtp.gmail.com with ESMTPSA id ja5-20020a170902efc500b001930b189b32sm883146plb.189.2023.01.23.23.16.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jan 2023 23:16:10 -0800 (PST) Date: Tue, 24 Jan 2023 12:46:02 +0530 From: Manivannan Sadhasivam To: kishon@kernel.org, lpieralisi@kernel.org, bhelgaas@google.com Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kw@linux.com, robh@kernel.org, vidyas@nvidia.com, vigneshr@ti.com Subject: Re: [PATCH v5 0/5] PCI: endpoint: Rework the EPC to EPF notification Message-ID: <20230124071602.GB4947@thinkpad> References: <20230124071158.5503-1-manivannan.sadhasivam@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230124071158.5503-1-manivannan.sadhasivam@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 24, 2023 at 12:41:53PM +0530, Manivannan Sadhasivam wrote: > Hello, > > During the review of the patch that fixes DBI access in PCI EP, Rob > suggested [1] using a fixed interface for passing the events from EPC to > EPF instead of the in-kernel notifiers. > > This series introduces a simple callback based mechanism for passing the > events from EPC to EPF. This interface is chosen for satisfying the below > requirements: > > 1. The notification has to reach the EPF drivers without any additional > latency. > 2. The context of the caller (EPC) needs to be preserved while passing the > notifications. > > With the existing notifier mechanism, the 1st case can be satisfied since > notifiers aren't adding any huge overhead. But the 2nd case is clearly not > satisfied, because the current atomic notifiers forces the EPF > notification context to be atomic even though the caller (EPC) may not be > in atomic context. In the notification function, the EPF drivers are > required to call several EPC APIs that might sleep and this triggers a > sleeping in atomic bug during runtime. > > The above issue could be fixed by using a blocking notifier instead of > atomic, but that proposal was not accepted either [2]. > > So instead of working around the issues within the notifiers, let's get rid > of it and use the callback mechanism. > > NOTE: DRA7xx and TEGRA194 drivers are only compile tested. Testing this series > on the real platforms is greatly appreciated. > Lorenzo, all patches in this series got review tags. Can you please merge now? Thanks, Mani > Thanks, > Mani > > [1] https://lore.kernel.org/all/20220802072426.GA2494@thinkpad/T/#mfa3a5b3a9694798a562c36b228f595b6a571477d > [2] https://lore.kernel.org/all/20220228055240.24774-1-manivannan.sadhasivam@linaro.org > > Changes in v5: > > * Collected review tag from Vidya > * Fixed the issue reported by Kbot regarding missing declaration > > Changes in v4: > > * Added check for the presence of event_ops before involing the callbacks (Kishon) > * Added return with IRQ_WAKE_THREAD when link_up event is found in the hard irq > handler of tegra194 driver (Vidya) > * Collected review tags > > Changes in v3: > > * As Kishon spotted, fixed the DRA7xx driver and also the TEGRA194 driver to > call the LINK_UP callback in threaded IRQ handler. > > Changes in v2: > > * Introduced a new "list_lock" for protecting the epc->pci_epf list and > used it in the callback mechanism. > > Manivannan Sadhasivam (5): > PCI: dra7xx: Use threaded IRQ handler for "dra7xx-pcie-main" IRQ > PCI: tegra194: Move dw_pcie_ep_linkup() to threaded IRQ handler > PCI: endpoint: Use a separate lock for protecting epc->pci_epf list > PCI: endpoint: Use callback mechanism for passing events from EPC to > EPF > PCI: endpoint: Use link_up() callback in place of LINK_UP notifier > > drivers/pci/controller/dwc/pci-dra7xx.c | 2 +- > drivers/pci/controller/dwc/pcie-tegra194.c | 9 ++++- > drivers/pci/endpoint/functions/pci-epf-test.c | 38 ++++++------------- > drivers/pci/endpoint/pci-epc-core.c | 32 ++++++++++++---- > include/linux/pci-epc.h | 10 +---- > include/linux/pci-epf.h | 19 ++++++---- > 6 files changed, 59 insertions(+), 51 deletions(-) > > -- > 2.25.1 > -- மணிவண்ணன் சதாசிவம்