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SubjectRe: [PATCH v11 3/3] PCI: uniphier: Add misc interrupt handler to invoke PME and AER
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Hi Pali,

Thank you for considering about my patch.

On 2021/07/18 9:26, Pali Rohar wrote:

> Hello Kunihiko!
>
> On Friday 23 April 2021 02:04:57 Kunihiko Hayashi wrote:
> > This patch adds misc interrupt handler to detect and invoke PME/AER event.
> >
> > In UniPhier PCIe controller, PME/AER signals are assigned to the same
> > signal as MSI by the internal logic. These signals should be detected by
> > the internal register, however, DWC MSI handler can't handle these signals.
> >
> > DWC MSI handler calls .msi_host_isr() callback function, that detects
> > PME/AER signals using the internal register and invokes the interrupt
> > with PME/AER IRQ numbers.
> >
> > These IRQ numbers is obtained by uniphier_pcie_port_get_irq() function,
> > that finds the device that matches PME/AER from the devices associated
> > with Root Port, and returns its IRQ number.
>
> If I understood this issue correctly, it means that your PCIe controller
> does not issue regular MSI interrupt for PME and AER events, but rather
> it issue controller specific interrupt and you need to figure out what
> kind of controller-specific event happened (e.g. PME or AER or something
> else).

Your view is almost correct.
This controller consists of Synopsys DWC and the glue logic, and regular
MSI interrupt is handled in dw_pcie_msi_isr() for DWC.

The interrupt for PME/AER event is issued to CPU as the same interrupt
as MSI, though, PME/AER event is detected by the glue logic instead of DWC.
So the regular MSI handler can't handle the interrupt for PME/AER event
directly.


> But if your controller supports PME or AER then it expose in its PCIe
> Root Port capabilities register MSI number for these PME and AER events.
> Kernel PCIe PME and AER drivers read from capabilities register these
> numbers and register irq functions to be called when interrupt happens.

Yes, the controller also has the MSI number for PME/AER in Root Port
capability register (defined as PCI_ERR_ROOT_AER_IRQ and PCI_EXP_FLAGS_IRQ).

These interrupts are registered with these capability values in
pcie_port_enable_irq_vec().


> So it means that you do not need to implement uniphier_pcie_port_get_irq
> function via this "ugly" foreach and call pcie_port_service_get_irq. But
> you can read this MSI interrupt number directly from your controller in
> this pcie-uniphier.c driver and then use irq_find_mapping() to convert
> hw MSI number to kernel's virq (used in generic_handle_irq()).
>
> Because currently you use in pcie-uniphier.c call to function
> pcie_port_service_get_irq() which returns cached interrupt number value
> which was read from PCIe Root Port capability register by PCI subsystem
> callbacked back to the pcie-uniphier.c driver.
>
> For me this looks like "ugly" if you need to do something in
> "complicated" way and add dependency e.g. on compile options like
> "if (!IS_ENABLED(CONFIG_PCIEAER) && !IS_ENABLED(CONFIG_PCIE_PME))" if it
> can be easily avoided.
>
> I'm writing this because I was solving exactly same problem for aardvark
> PCIe controller with PME, AER and HP interrupts (patches are on ML). So
> I think that this pcie-uniphier.c implementation can be simplified
> without need to use checks for CONFIG_* options and calling
> pcie_port_service_get_irq() in list_for_each_entry loop.

The interrupt for PME/AER event is detected by the glue logic.

When the handler needs to read the status register for PME/AER in the glue
logic and issue the correspond MSI interrupt using generic_handle_irq().

If the driver gets the MSI interrupt number directly like
pcie_message_numbers() function, I think this complicated method is
no longer necessary, too.


> Could you please post output of 'lspci -nn -vv'? In my opinion MSI
> numbers for AER and PME in Root Port could be constant so it may
> simplify implementation even more. (Just to note that in my case
> aardvark returns zero as MSI number and it is also documented in spec).

I already posted the lspci output[1].

[1]
https://lore.kernel.org/linux-pci/1592469493-1549-3-git-send-email-hayashi.kunihiko@socionext.com/T/#e1145dab891debed1eadcddbf2b9f5fabb357f8b0

According to the spec, the initial MSI number for PME/AER is zero.
And this series up to v5 used fixed zero as the MSI number for PME/AER.

Thank you,

---
Best Regards
Kunihiko Hayashi

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