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 AB70AC433FE for ; Mon, 14 Nov 2022 07:33:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235667AbiKNHd1 (ORCPT ); Mon, 14 Nov 2022 02:33:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235468AbiKNHd0 (ORCPT ); Mon, 14 Nov 2022 02:33:26 -0500 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 864F2B2 for ; Sun, 13 Nov 2022 23:33:23 -0800 (PST) Received: by mail-pf1-x436.google.com with SMTP id b185so10219544pfb.9 for ; Sun, 13 Nov 2022 23:33:23 -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=ci7EEHbshcFehJfZ1vhA/3zbDhlLQ5SlERB0/duNlh8=; b=y3sTF4hmY4khAQzxD5W0lpR+G1orJovJ5WNYYWsHTSyjMcgBjhMkaiOKdjckMTBiSh vh2JE+gHWRkYtjJoGRqNcDFThmcgZ3HDTXz4t768hG1xHySziZr6AG6FeEXAHrWsdLcY SoFCnu7xK8reZ4yDWPnDrdBf/SDCBNPE+xlm3Qsz/JZglETSwzmQ5uRroMSLDpE3gk/e Qt9aUnUTI21HApCAfmG9Ea0xI5FsXzBMCinDKk0fGzcoHt1oqpAXXut11zfY0T/wZcol 5gaB+iO7F/tNZyVlMi2ANbPrZljhp4bUCyrGnGb4yq2dlMZhj3TYphO8NvVFGWUy0HW7 gB4g== 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=ci7EEHbshcFehJfZ1vhA/3zbDhlLQ5SlERB0/duNlh8=; b=1UNoZ7Z3vEPqZFoNGraM62NdpmGo+feHuDVolFU9G9XnL5kqNaQnTmSyOakmyEuNVL j16YRgex+Avcd92+s0ykUcQFS4n4tirI4oNdwQI6CLezbSNriBMMT9810Ym4czA6e/69 wQc+/qisE8GZ4iRfUvWLt8z5gtIUyyEtdIVzqsWpXzkpjoMpD3WLTg4YX9T+mjlOee9N ngPRT0cSYOjaDYs/Atw+j8NRsHHIDhBuL4YfAOzUet0LfLWa48pOqYOd/gQx8rCAepyw 6GGkw5t7BGfqrJr2+Ggfob+uGWt2WtCV3el1Ax8jFPAEbbIivb8T3aPHDI7/6FI/GtW7 AGYQ== X-Gm-Message-State: ANoB5plFc0VsxMng9Zz8olHKE43XZB1kBxVnl0Gr6DqCRHRiQ6VhrsOG 176Pj7VV5OnvwGgnpRcypqJQ X-Google-Smtp-Source: AA0mqf7pnXSPJUmcLy5E7oq1swZ5WkTvgCA6ttdHUuKrnr9k9Qhvivs0XObyuY2+UptCt2a0b/0dqg== X-Received: by 2002:aa7:8813:0:b0:56b:f64b:b385 with SMTP id c19-20020aa78813000000b0056bf64bb385mr12648979pfo.68.1668411202990; Sun, 13 Nov 2022 23:33:22 -0800 (PST) Received: from thinkpad ([117.248.0.54]) by smtp.gmail.com with ESMTPSA id w7-20020a654107000000b0043ae1797e2bsm5215425pgp.63.2022.11.13.23.33.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Nov 2022 23:33:21 -0800 (PST) Date: Mon, 14 Nov 2022 13:03:16 +0530 From: Manivannan Sadhasivam To: lpieralisi@kernel.org Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kw@linux.com, robh@kernel.org, vidyas@nvidia.com, vigneshr@ti.com, kishon@kernel.org, bhelgaas@google.com Subject: Re: [PATCH v4 0/5] PCI: endpoint: Rework the EPC to EPF notification Message-ID: <20221114073316.GI3869@thinkpad> References: <20221025145101.116393-1-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: <20221025145101.116393-1-manivannan.sadhasivam@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Oct 25, 2022 at 08:20:56PM +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, can this series be merged for v6.2 since all the patches are reviewed 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 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