[PATCH] PCI/MSI: mvebu: Re-enable arch fallbacks

[Domenico Andreoli]

On Wed, Mar 16, 2022 at 11:37:14AM +0000, Marc Zyngier wrote:
> On 2022-03-16 09:33, Domenico Andreoli wrote:
> > From: Domenico Andreoli <domenico.andreoli at linux.com>
> > 
> > Since v5.10, my QNAP happily barks at boot as follows (5.17.0-rc8):
> > 
> > [    0.923811] ------------[ cut here ]------------
> > [    0.928458] WARNING: CPU: 0 PID: 1 at drivers/pci/msi/msi.h:17
> > pci_msi_setup_msi_irqs+0x54/0x6c
> > [    0.937219] Modules linked in:
> > [    0.940290] CPU: 0 PID: 1 Comm: swapper Not tainted
> > 5.17.0-rc8-marvell #6
> > [    0.947117] Hardware name: Marvell Kirkwood (Flattened Device Tree)
> > [    0.953428]  unwind_backtrace from show_stack+0x10/0x14
> > [    0.958698]  show_stack from __warn+0xac/0xe4
> > [    0.963093]  __warn from warn_slowpath_fmt+0x68/0x80
> > [    0.968098]  warn_slowpath_fmt from pci_msi_setup_msi_irqs+0x54/0x6c
> > [    0.974499]  pci_msi_setup_msi_irqs from
> > __pci_enable_msi_range+0x260/0x340
> > [    0.981509]  __pci_enable_msi_range from
> > pci_alloc_irq_vectors_affinity+0xb8/0xf8
> > [    0.989043]  pci_alloc_irq_vectors_affinity from xhci_run+0x164/0x474
> > [    0.995532]  xhci_run from usb_add_hcd+0x444/0x6e0
> > [    1.000362]  usb_add_hcd from usb_hcd_pci_probe+0x30c/0x37c
> > [    1.005979]  usb_hcd_pci_probe from xhci_pci_probe+0x10/0xec
> > [    1.011689]  xhci_pci_probe from pci_device_probe+0x74/0xe8
> > [    1.017305]  pci_device_probe from really_probe+0x1c0/0x3f8
> > [    1.022921]  really_probe from driver_probe_device+0x30/0xb0
> > [    1.028623]  driver_probe_device from __driver_attach+0x11c/0x148
> > [    1.034762]  __driver_attach from bus_for_each_dev+0x54/0x78
> > [    1.040466]  bus_for_each_dev from bus_add_driver+0x170/0x1d8
> > [    1.046256]  bus_add_driver from driver_register+0xac/0xf0
> > [    1.051783]  driver_register from do_one_initcall+0x74/0x1b8
> > [    1.057495]  do_one_initcall from kernel_init_freeable+0x1a8/0x1ec
> > [    1.063723]  kernel_init_freeable from kernel_init+0x10/0x108
> > [    1.069514]  kernel_init from ret_from_fork+0x14/0x3c
> > [    1.074604] Exception stack(0xc1835fb0 to 0xc1835ff8)
> > [    1.079691] 5fa0:                                     00000000
> > 00000000 00000000 00000000
> > [    1.087915] 5fc0: 00000000 00000000 00000000 00000000 00000000
> > 00000000 00000000 00000000
> > [    1.096136] 5fe0: 00000000 00000000 00000000 00000000 00000013
> > 00000000
> > [    1.102787] ---[ end trace 0000000000000000 ]---
> > [    1.107435] ------------[ cut here ]------------
> > 
> > 
> > I bisected it down to commit 077ee78e392869e46ae (PCI/MSI: Make
> > arch_.*_msi_irq[s] fallbacks selectable).
> > 
> > Re-enabling PCI/MSI arch fallbacks restores a clean bootlog.
> > 
> > Cc: Thomas Gleixner <tglx at linutronix.de>
> > Cc: linux-arm-kernel at lists.infradead.org
> > Signed-off-by: Domenico Andreoli <domenico.andreoli at linux.com>
> > 
> > ---
> >  arch/arm/mach-mvebu/Kconfig |    1 +
> >  1 file changed, 1 insertion(+)
> > 
> > Index: b/arch/arm/mach-mvebu/Kconfig
> > ===================================================================
> > --- a/arch/arm/mach-mvebu/Kconfig
> > +++ b/arch/arm/mach-mvebu/Kconfig
> > @@ -123,6 +123,7 @@ config MACH_KIRKWOOD
> >  	select ORION_IRQCHIP
> >  	select ORION_TIMER
> >  	select FORCE_PCI
> > +	select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
> >  	select PCI_QUIRKS
> >  	select PINCTRL_KIRKWOOD
> >  	help
> 
> This really is papering over the real issue, which probably is
> that the platform *doesn't* support MSIs, and yet the PCI
> controller driver doesn't advertises that.

I'll investigate this.

> 
> See 645e9c38383d ("PCI: mediatek: Advertise lack of built-in MSI
> handling") for an example of how to fix your PCI controller driver.

Thanks for the pointer!

Dom

> 
> Thanks,
> 
>         M.
> -- 
> Jazz is not dead. It just smells funny...

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