Per USB device interrupt handler for xhci

Per USB device interrupt handler for xhci

[yunhua li]

Hi  all

xhci_msi_irq is the interrupt handler for xhci, the controller it self
is a PCI device, on my system it is a Intel chip. I have multiple USB
device connect to this USB host controller,  xhci_msi_irq is interrupt
handler for the PCI device(USB Host controller).
Is it possible to have multiple IRQ, and different IRQ for different
USB device? If so how? the chip(USB Host controller) should know which
USB device’s transaction,
When the chip decide to assert an interrupt, it should be a reason for
a specified USB device, then assert a correspondence MSI interrupt.
Thanks.

sudo lspci -s 00:14.0 -v
00:14.0 USB controller: Intel Corporation Device a2af (prog-if 30 [XHCI])
        Subsystem: Dell Device 0738
        Flags: bus master, medium devsel, latency 0, IRQ 29
        Memory at 38003ff10000 (64-bit, non-prefetchable) [size=64K]
        Capabilities: [70] Power Management version 2
        Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
        Kernel driver in use: xhci_hcd



Regards

Re: Per USB device interrupt handler for xhci

[Greg KH]

On Fri, Jul 05, 2019 at 07:50:28PM -0700, yunhua li wrote:
> Hi  all
> 
> xhci_msi_irq is the interrupt handler for xhci, the controller it self
> is a PCI device, on my system it is a Intel chip. I have multiple USB
> device connect to this USB host controller,  xhci_msi_irq is interrupt
> handler for the PCI device(USB Host controller).
> Is it possible to have multiple IRQ, and different IRQ for different
> USB device?

Nope.  That is not how USB works.  Please read the xhci spec if you are
curious as to why.

greg k-h

Re: Per USB device interrupt handler for xhci

[yunhua li]

Thank you Greg, So it seems xhci's interrupt based on it's rx/tx
queue(ring), the ring is shared by all USB device,  it is not aware of
"per USB device"?

Regards
Yunhua

On Fri, Jul 5, 2019 at 9:46 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Fri, Jul 05, 2019 at 07:50:28PM -0700, yunhua li wrote:
> > Hi  all
> >
> > xhci_msi_irq is the interrupt handler for xhci, the controller it self
> > is a PCI device, on my system it is a Intel chip. I have multiple USB
> > device connect to this USB host controller,  xhci_msi_irq is interrupt
> > handler for the PCI device(USB Host controller).
> > Is it possible to have multiple IRQ, and different IRQ for different
> > USB device?
>
> Nope.  That is not how USB works.  Please read the xhci spec if you are
> curious as to why.
>
> greg k-h