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Fri, 25 Jun 2021 00:09:38 -0700 (PDT) Received: from [192.168.1.101] ([92.176.231.106]) by smtp.gmail.com with ESMTPSA id i18sm1603468wrw.55.2021.06.25.00.09.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Jun 2021 00:09:38 -0700 (PDT) Subject: Re: [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated To: Bjorn Helgaas Cc: linux-kernel@vger.kernel.org, Peter Robinson , Shawn Lin , Bjorn Helgaas , Heiko Stuebner , Lorenzo Pieralisi , Rob Herring , linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org, Michal Simek , Ley Foon Tan , rfi@lists.rocketboards.org, Jingoo Han , Thierry Reding , Jonathan Hunter , linux-tegra@vger.kernel.org References: <20210624224040.GA3567297@bjorn-Precision-5520> From: Javier Martinez Canillas Message-ID: <5bee3702-595b-f57b-f962-28644b7e646f@redhat.com> Date: Fri, 25 Jun 2021 09:09:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210624224040.GA3567297@bjorn-Precision-5520> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=javierm@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210625_000943_866533_6A20F00A X-CRM114-Status: GOOD ( 34.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Bjorn, On 6/25/21 12:40 AM, Bjorn Helgaas wrote: > [+cc Michal, Ley Foon, Jingoo, Thierry, Jonathan] > > On Tue, Jun 08, 2021 at 10:04:09AM +0200, Javier Martinez Canillas wrote: >> IRQ handlers that are registered for shared interrupts can be called at >> any time after have been registered using the request_irq() function. >> >> It's up to drivers to ensure that's always safe for these to be called. >> >> Both the "pcie-sys" and "pcie-client" interrupts are shared, but since >> their handlers are registered very early in the probe function, an error >> later can lead to these handlers being executed before all the required >> resources have been properly setup. >> >> For example, the rockchip_pcie_read() function used by these IRQ handlers >> expects that some PCIe clocks will already be enabled, otherwise trying >> to access the PCIe registers causes the read to hang and never return. >> >> The CONFIG_DEBUG_SHIRQ option tests if drivers are able to cope with their >> shared interrupt handlers being called, by generating a spurious interrupt >> just before a shared interrupt handler is unregistered. >> >> But this means that if the option is enabled, any error in the probe path >> of this driver could lead to one of the IRQ handlers to be executed. > > I'm not an IRQ expert, but I think this is an issue regardless of > CONFIG_DEBUG_SHIRQ, isn't it? Anything used by an IRQ handler should > be initialized before the handler is registered. CONFIG_DEBUG_SHIRQ > is just a way to help find latent problems. > Yes, it's an issue regardless. It's just that this debug option tests if the drivers aren't making the wrong assumption, exactly to find issues like this. >> In a rockpro64 board, the following sequence of events happens: >> >> 1) "pcie-sys" IRQ is requested and its handler registered. >> 2) "pcie-client" IRQ is requested and its handler registered. >> 3) probe later fails due readl_poll_timeout() returning a timeout. >> 4) the "pcie-sys" IRQ is unregistered. >> 5) CONFIG_DEBUG_SHIRQ triggers a spurious interrupt. >> 6) "pcie-client" IRQ handler is called for this spurious interrupt. >> 7) IRQ handler tries to read PCIE_CLIENT_INT_STATUS with clocks gated. >> 8) the machine hangs because rockchip_pcie_read() call never returns. >> >> To avoid cases like this, the handlers don't have to be registered until >> very late in the probe function, once all the resources have been setup. >> >> So let's just move all the IRQ init before the pci_host_probe() call, that >> will prevent issues like this and seems to be the correct thing to do too. > > Previously we registered rockchip_pcie_subsys_irq_handler() and > rockchip_pcie_client_irq_handler() before the PCIe clocks were > enabled. That's a problem because they depend on those clocks being > enabled, and your patch fixes that. > > rockchip_pcie_legacy_int_handler() depends on rockchip->irq_domain, > which isn't initialized until rockchip_pcie_init_irq_domain(). > Previously we registered rockchip_pcie_legacy_int_handler() as the > handler for the "legacy" IRQ before rockchip_pcie_init_irq_domain(). > > I think you patch *also* fixes that problem, right? > Correct, that's why I moved the initialization and IRQ enable after that. > I think this is also an issue with the following other drivers. They all > set the handler to something that uses an IRQ domain before they > actually initialize the domain: Yes, I agreed with your assessment and also noticed that others drivers have similar issues. I just don't have any of those platforms to try to reproduce the bugs and test a fix. Best regards, -- Javier Martinez Canillas Software Engineer New Platform Technologies Enablement team RHEL Engineering _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel