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 21411C4332F for ; Sat, 5 Nov 2022 06:53:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229531AbiKEGxv (ORCPT ); Sat, 5 Nov 2022 02:53:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50308 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229486AbiKEGxu (ORCPT ); Sat, 5 Nov 2022 02:53:50 -0400 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83269140D6 for ; Fri, 4 Nov 2022 23:53:48 -0700 (PDT) Received: by mail-pg1-x529.google.com with SMTP id q71so6145137pgq.8 for ; Fri, 04 Nov 2022 23:53:48 -0700 (PDT) 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=spqUCiWZo+MTX7gTrHIIYbpr2WVSxFKmPwib1nju6j0=; b=vCsvXpteUbvdxcyhUwgBbkS7JDK6vIpRhapWfumJik5YymwhByNlMCGeqSpgXhYw/k wDAhJUnTJ/l/8ChQJqwHBBFbVYrAFz+455zA+u0J0vFq3+Fv0oPXyO2Yo8yYsJZJPc4F ybr/mELOAE7KFyRqYOJ9RUdN5nX2MCQQqK/eClhpf3tbtSaW9MUZKtIovYnK6dJkwwRD wJNgSKT39a10xwVasH257lJNRPFoRPFhxQiLpHNT1CrXpT4xCGyjuVpmenkcuZPB2hUT Zlfx6JET0RzcNOVxswtJ07cWDEZ47vLdJIcx1+NTdICsw3z23Olq4g1QGEE8ybOFUGGr Uvdw== 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=spqUCiWZo+MTX7gTrHIIYbpr2WVSxFKmPwib1nju6j0=; b=6pXEuiakCXqopcB+WSU2cEcOHByoqsKmpU3rVBOhwI3Fv4cnXx9Fz25Fk0zjmbNtkE r9gNt59rD75f8B0uZbtawhj3kWaejTpCOZ5W31UN88H68JSLUjTZob5hoYVMxNb1WILA pVkskxt87x+3RPUu6RD+77Ps9bNZBK5BhYeRJ1XIZ1hIU00IStFARfwftwjVnUxv9mB+ rc3lV5Hky+SlfIcsWq/fyWbKQo0sk5+Dy+LgXnTN7oxMMLiJPgcXBkhfHAhViCQCu+Hi 5JkfP3IPAGrrpbREsTD1OEfZTcve3GdoAdhP/BE4+1NoKxhyLZgqo8acK72FLHvkCH1y +FWA== X-Gm-Message-State: ACrzQf3OoRjzkNjhonDtoP77g5+Wqpdfi4KAsMC3XMWQIX3tKjREuuu7 yXOEXxpIYVW8KGreIw9aGPf4sDiwHETj X-Google-Smtp-Source: AMsMyM5N2FhE/o8kj7rOhMh6xZCjBZiv0KSswsPslcJfG88j0WMERTeAbn/Rt39M6TXAOBiCJvxgqA== X-Received: by 2002:a05:6a00:24cb:b0:56c:7815:bc7d with SMTP id d11-20020a056a0024cb00b0056c7815bc7dmr39946304pfv.44.1667631227974; Fri, 04 Nov 2022 23:53:47 -0700 (PDT) Received: from thinkpad ([117.217.186.6]) by smtp.gmail.com with ESMTPSA id v126-20020a626184000000b00565cf8c52c8sm666527pfb.174.2022.11.04.23.53.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Nov 2022 23:53:45 -0700 (PDT) Date: Sat, 5 Nov 2022 12:23:37 +0530 From: Manivannan Sadhasivam To: kishon@kernel.org, lpieralisi@kernel.org, bhelgaas@google.com, kvijayab@amd.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 v4 0/5] PCI: endpoint: Rework the EPC to EPF notification Message-ID: <20221105065337.GA109545@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 Hi Kishon, 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. > Any feedback on this series? 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