Re: [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated

[Javier Martinez Canillas]

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.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer
New Platform Technologies Enablement team
RHEL Engineering