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 DAC1DC43217 for ; Mon, 14 Nov 2022 10:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235546AbiKNKHb (ORCPT ); Mon, 14 Nov 2022 05:07:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236977AbiKNKGf (ORCPT ); Mon, 14 Nov 2022 05:06:35 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDB2A1FCD2; Mon, 14 Nov 2022 02:05:52 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BFDB960F9D; Mon, 14 Nov 2022 10:05:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5F3EC433D6; Mon, 14 Nov 2022 10:05:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668420351; bh=7U/JLGLVqG5uJOPAiWuJklR/LVbjzuDSTvLSKgNm8AA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Q6yeJPHIViXWhZoIGEGrkqT0iRrRlHWhfKb0+YXQ1H/5/TEYjouUp+1ZXwO+1YjkQ YTdDg5kWSY55YILXkx6jKFznnm0NSnzmQe/YVebaK5UtkQ82xhQFN1nSeXlKuj54IS 6lqo8MA76aTAUnr/89AHm55PHhgFd939Rp4RC5XdvATvhRwzBLGizC/+7kD5CHnKui ULvPZayeqvKrKjOBTkn2Bf40WJlySGqfWMSBb9HYnRU47h3ZzLZodeTyqKYGpumGa6 vTi70NKErwmJPqZiQflFirKsWNTrYHYCrcDOxHOJiolW+wixyd/RIpSh8fCvVDo8hb QG6toxsylzhog== Date: Mon, 14 Nov 2022 11:05:44 +0100 From: Lorenzo Pieralisi To: Manivannan Sadhasivam 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: References: <20221025145101.116393-1-manivannan.sadhasivam@linaro.org> <20221114073316.GI3869@thinkpad> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221114073316.GI3869@thinkpad> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Nov 14, 2022 at 01:03:16PM +0530, Manivannan Sadhasivam wrote: > 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? Patch (2) isn't (or I missed something) - we should be looking for review/testing on it. Thanks, Lorenzo > 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