Setting cpu affinity for MSI-X on i.mx6 possible?

[Lucas Stach]

Am Montag, den 27.10.2014, 20:16 +0100 schrieb Heiner Kallweit:
> Thanks, Lucas.
> 
> It's interesting however that the igb driver claims it's using MSI-X.
> Maybe the DW PCIE drivers offers MSI-X on the bus and just internally falls back to MSI?
> 
Are you running a upstream or downstream vendor kernel?
On my upstream kernel igb properly falls back to MSI.

Regards,
Lucas

> Rgds, Heiner
> 
> [    4.165850] igb: Intel(R) Gigabit Ethernet Network Driver - version 5.2.15-k
> [    4.172930] igb: Copyright (c) 2007-2014 Intel Corporation.
> [    4.178638] igb 0000:01:00.0: enabling device (0140 -> 0142)
> [    4.235789] igb 0000:01:00.0: added PHC on eth0
> [    4.235793] igb 0000:01:00.0: Intel(R) Gigabit Ethernet Network Connection
> [    4.235799] igb 0000:01:00.0: eth0: (PCIe:2.5Gb/s:Width x1) 00:01:c0:14:b1:58
> [    4.235804] igb 0000:01:00.0: eth0: PBA No: FFFFFF-0FF
> [    4.235810] igb 0000:01:00.0: Using MSI-X interrupts. 2 rx queue(s), 2 tx queue(s)
> 
> 
> Am 27.10.2014 um 09:52 schrieb Lucas Stach:
> > Hello Heiner,
> > 
> > Am Sonntag, den 26.10.2014, 19:05 +0100 schrieb Heiner Kallweit:
> >> I use a mini pc with i.mx6 dual and Intel igb based nic (I211) connected via PCIE.
> >> igb driver uses MSI-X and creates two rx/tx queue pairs. However the IRQs of all queues are handled by the same CPU.
> >> Changing affinity is not possible. Obvious direct reason is that irq_chip PCI-MSI doesn't implement the callback
> >> for setting cpu affinity.
> >> I'd appreciate a hint whether this is a general limitation of the Cortex-A9 / GICv1 / Synopsys Designware
> >> architecture or whether just a proper implementation is missing yet.
> >>
> >> Rgds, Heiner
> > 
> > The MSI controller on imx6 doesn't support MSI-X so igb falls back to
> > regular MSI interrupts. Also all MSI interrupts are aggregated into a
> > single GIC interrupt line. This means the best we could do is switch all
> > PCIe MSI interrupts to some other CPU. Configuring the CPU affinity on a
> > per interrupt basis is impossible on this hardware.
> > 
> > Regards,
> > Lucas
> > 
> 
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Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |