[Bug 53637] New: Interference between KMS/RV515 and external firewire hardware (ffado device).

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=53637

             Bug #: 53637
           Summary: Interference between KMS/RV515 and external firewire
                    hardware (ffado device).
    Classification: Unclassified
           Product: xorg
           Version: unspecified
          Platform: x86-64 (AMD64)
        OS/Version: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: Driver/Radeon
        AssignedTo: xorg-driver-ati at lists.x.org
        ReportedBy: inaudible at simplesuperlativ.es
         QAContact: xorg-team at lists.x.org


I am experiencing an issue with the radeon kernel driver in relation to an
external audio device (Edirol FA-101). The device is driven by Jack/FFADO
(http://ffado.org) connected to a TI pcmcia firewire card, and running into a
TI cardbus controller. 

I have reported this problem to the ffado-users mailing-list and you can see
the thread archived here:
http://sourceforge.net/mailarchive/message.php?msg_id=29666161

I have previously used the device on a dedicated and infrequently updated
debian linux partition, which was running stable for a long time. Unfortunately
this setup was lost to a failing disk, and now I am attempting to run the
device on an up-to-date archlinux distribution.

The bug basically causes a loss in sync between the streaming server
(Jack/FFADO) and the system bus when there is a certain kind of 2d-graphic
update. 

I have tested this against as many kernels as possible and the last working
kernel is the 2.6.32-lts distributed by archlinux. The first kernel that I can
install where this bug appears is 2.6.34 (2.6.33 fails to boot because it was
not compiled with DEVTMPFS support, and attempts to compile it failed as there
are numerous incompatibilities with later gcc versions). The most optimum
environment is using the usb-live distro 'pure:dyne' (ubuntu based) which is
running 2.6.31 (RT PREEMPT) - this probably most closely replicates the
performance I had previously.

The bug occurs when audio is streaming to the device, and there is an update to
a 2D window, it is not the case with all 2D software, only some. Some scenerios
where I can demonstrate this bug include:
Resizing window geometry (any window).
Typing a message in Evolution (GTK), each new line creates a dropout.
Repeated updates to Xorg/XTerm ('cat /var/log/messages' or 'top')
Various manipulations to the software Fontforge (internal toolkit)
Moving objects around a canvas in Pure Data (TCL/TK).

Pure Data is the software I typically use for DSP processing, so it's
frustrating that it has such a profound effect, doing any basic manipulation to
the window makes the bug appear regardless of if it's running a DSP chain or
not (the software can be run without audio).

This led me to test TCL/TK, and it can create a full dropout and disconnect of
the streaming server just by running a small repeating canvas animation found
here: http://wiki.tcl.tk/4293

A lot of other software seems to peacefully coexist - drawing with gimp or
inkscape, performing 3d compositing by gnome-shell, browsing in firefox or
chromium - all quite demanding tasks graphically - no dropouts.

I have found that switching off KMS (radeon.modeset=0) improves the situation,
with the dropouts (XRUNS) no longer being reported by Jack/FFADO but there is
still tearing in the audio itself, and all 2d functions run quite sluggishly
with KMS switched off.

I have attempted the following kernel settings without any improvements.
radeon.disp_priority=1
radeon.msi=0
video=LVDS-1:640x480
threadirqs

I'll attach as many related logs as possible, but please let me know what might
be useful to debug.

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