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SubjectRe: [PATCH] PCI: controller: dwc: Make PCI_IMX6 depend on PCIEPORTBUS
On 2018-12-06 9:50 a.m., Lucas Stach wrote:
> Am Donnerstag, den 06.12.2018, 09:45 -0600 schrieb Robert Hancock:
>> On 2018-12-06 2:10 a.m., Baruch Siach wrote:
>>> Hi Andrey,
>>> Adding Robert Hancock who reported[1] on a PCIe MSI issue with i.MX6.
>>> Andrey Smirnov writes:
>>>> Building a kernel with CONFIG_PCI_IMX6=y, but CONFIG_PCIEPORTBUS=n
>>>> produces a system where built-in PCIE bridge (16c3:abcd) isn't bound
>>>> to pcieport driver. This, in turn, results in a PCIE bus that is
>>>> capable of enumerating attached PCIE device, but lacks functional
>>>> interrupt support.
>>> Robert, does that fix your issue?
>> Unfortunately, no.. in fact the situation on my setup is even worse with
>> CONFIG_PCIEPORTBUS enabled: Not only does MSI still not function, but
>> now INTx interrupts are somehow broken as well - no interrupts are
>> received. The IRQ information shown in /proc/interrupts is correct, but
>> the count remains stubbornly at 0.
> That's expected. The port services will use an MSI IRQ when available
> and due to a design issue with the DWC PCIe it will not forward any
> legacy IRQs if any MSI is in use. If any of the PCIe devices in your
> system are unable to work with MSI IRQs, you must boot with "nomsi" on
> the kernel command line set.

That seems like an unfortunate design choice on their part.. well that
would probably argue against adding this as a hard dependency then, if
non-MSI-supporting PCIe devices can't work with default boot options
with that set.

I'm looking into testing with an NXP Smart Devices board and some PCIe
cards to see if I can verify whether MSI works on those or not, since we
currently don't have a way to independently verify that the MSI
implementation in our FPGA is working or whether another PCIe device
works with MSI (the FPGA is integrated on the system board).

Robert Hancock
Senior Software Developer
SED Systems

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