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
