On Mon, December 4, 2017 2:44 pm, Chris Caudle wrote:
> OK, I guess that is good in general for PlanetCCRMA, but I still don't
> have any good place to start with no error messages. I don't know where
> to even start debugging a driver problem.
Just to follow up in case this helps someone else some day:
I tried the same interface on a different machine running the same kernel,
no problems, found just as Fernando did that the kernel in general has no
problem with USB interfaces.
Back to the original machine, works fine on standard kernel (which in the
case of Fedora does not enable CONFIG_PREEMPT, only
CONFIG_PREEMPT_VOLUNTARY, so I think that may mean no threadirq support).
Still unusable on RT.
I changed the physical USB port in use, and now the interface works. I'm
not completely sure yet why that is the case. These are some clues I
have:
message from syslogd@chubb at Dec 9 13:00:02 ...
kernel:Disabling IRQ #20
So something is causing a problem from IRQ 20 and the kernel had to
disable that IRQ.
These are the RT priorities for IRQ:
$ rtirq status
PID CLS RTPRIO NI PRI %CPU STAT COMMAND
215 FF 95 - 135 0.0 S irq/20-uhci_hcd
217 FF 94 - 134 0.0 S irq/22-uhci_hcd
216 FF 93 - 133 0.0 S irq/23-uhci_hcd
219 FF 93 - 133 0.0 S irq/22-uhci_hcd
1257 FF 93 - 133 0.0 S irq/55-enp3s4f1
218 FF 92 - 132 0.0 S irq/23-uhci_hcd
222 FF 91 - 131 0.0 S irq/1-i8042
221 FF 90 - 130 0.0 S irq/12-i8042
But wait, there is a non-RT thread later on the same IRQ:
214 FF 50 - 90 0.0 S irq/20-ehci_hcd
So this connection did not work:
$ lsusb
Bus 006 Device 002: ID 03f0:1027 Hewlett-Packard Virtual keyboard and mouse
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 003: ID 1210:0009 DigiTech
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
but this connection did:
$ lsusb
Bus 006 Device 002: ID 03f0:1027 Hewlett-Packard Virtual keyboard and mouse
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 002: ID 1210:0009 DigiTech
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Tree view of non-working:
$ lsusb -t
/: Bus 06.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
|__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 1: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 12M
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
|__ Port 2: Dev 4, If 0, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 4, If 1, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 4, If 2, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 4, If 4, Class=Application Specific Interface,
Driver=, 12M
|__ Port 2: Dev 4, If 6, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 4, If 7, Class=Audio, Driver=snd-usb-audio, 12M
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/8p, 480M
Tree view of working:
$ lsusb -t
/: Bus 06.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
|__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 1: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 12M
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
|__ Port 2: Dev 2, If 0, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 2, If 1, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 2, If 2, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 2, If 4, Class=Application Specific Interface,
Driver=, 12M
|__ Port 2: Dev 2, If 6, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 2: Dev 2, If 7, Class=Audio, Driver=snd-usb-audio, 12M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/8p, 480M
I changed rtirq setup so that the interrupt 20 which is shared between the
ehci and uhci controllers is prioritized, just in case having the ehci at
lower priority was causing problems, but even with this still no usable
sound:
$ rtirq status
PID CLS RTPRIO NI PRI %CPU STAT COMMAND
214 FF 95 - 135 0.0 S irq/20-ehci_hcd
215 FF 95 - 135 0.0 S irq/20-uhci_hcd
217 FF 92 - 132 0.0 S irq/22-uhci_hcd
216 FF 91 - 131 0.0 S irq/23-uhci_hcd
219 FF 91 - 131 0.0 S irq/22-uhci_hcd
1257 FF 91 - 131 0.0 S irq/55-enp3s4f1
218 FF 90 - 130 0.0 S irq/23-uhci_hcd
222 FF 89 - 129 0.0 S irq/1-i8042
221 FF 88 - 128 0.2 S irq/12-i8042
tl;dr I can correct the problem by moving my USB interface to a
physically less convenient connector, but I do not really understand what
is happening in the drivers or kernel IRQ prioritization which makes that
so, and I do not understand why only the RT kernel has this problem and
not the PREEMPT_VOLUNTARY standard fedora kernel.
For now I have spent enough time today working on this, I will just move
the cable to the front connector on my machine, and hope I do not
accidentally bump into the cable and break the connector. Maybe later I
can find some information to explain the behavior.
--
Chris Caudle
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