Messages in this thread | | | Subject | Re: [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated | From | Robin Murphy <> | Date | Wed, 30 Jun 2021 10:44:44 +0100 |
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On 2021-06-30 00:14, Bjorn Helgaas wrote: > On Tue, Jun 29, 2021 at 11:52:44AM +0100, Robin Murphy wrote: >> On 2021-06-29 07:17, Javier Martinez Canillas wrote: >>> On 6/29/21 2:38 AM, Bjorn Helgaas wrote: >>>> On Thu, Jun 24, 2021 at 05:40:40PM -0500, Bjorn Helgaas wrote: >>> >>> [snip] >>> >>>>>> >>>>>> 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 your patch *also* fixes that problem, right? >>>> >>>> The lack of consistency in how we use >>>> irq_set_chained_handler_and_data() really bugs me. >>>> >>>> Your patch fixes the ordering issue where we installed >>>> rockchip_pcie_legacy_int_handler() before initializing data >>>> (rockchip->irq_domain) that it depends on. >>>> >>>> But AFAICT, rockchip still has the problem that we don't *unregister* >>>> rockchip_pcie_legacy_int_handler() when the rockchip-pcie module is >>>> removed. Doesn't this mean that if we unload the module, then receive >>>> an interrupt from the device, we'll try to call a function that is no >>>> longer present? >>> >>> Good question, I don't to be honest. I'll have to dig deeper on this but >>> my experience is that the module removal (and device unbind) is not that >>> well tested on ARM device drivers in general. >> >> Well, it does use devm_request_irq() so the handler should be unregistered >> by devres *after* ->remove has finished, however that does still leave a >> potential race window in which a pending IRQ could be taken during the later >> part of rockchip_pcie_remove() after it has started turning off critical >> things. Unless the clocks and regulators can also be delegated to devres, it >> might be more robust to explicitly manage the IRQs as well. Mixing the two >> schemes can be problematic when the exact order of both setup and teardown >> matters. > > I don't understand the devm_request_irq() connection. I'm looking at > this irq_set_chained_handler_and_data() call [1]: > > static int rockchip_pcie_setup_irq(struct rockchip_pcie *rockchip) > { > ... > irq = platform_get_irq_byname(pdev, "legacy"); > irq_set_chained_handler_and_data(irq, > rockchip_pcie_legacy_int_handler, > rockchip); > > irq = platform_get_irq_byname(pdev, "client"); > ... > > We look up "irq", pass it to irq_set_chained_handler_and_data(), and > throw it away without saving it anywhere. How would anything know how > to unregister rockchip_pcie_legacy_int_handler()? > > I could imagine irq_set_chained_handler_and_data() saving what's > needed for unregistration, but I would think that would require a > device pointer, which we don't give it. > > I'm IRQ-illiterate, so please educate me!
Oh, my mistake, I was looking at the "sys" and "client" IRQs and spoke too soon; the "legacy" IRQ does appear to be completely leaked as you say, so there are two degrees of issue here.
Robin.
> > Bjorn > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pcie-rockchip-host.c?id=v5.13#n562 >
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