Interrupt stom on cardbus device

[John Baldwin]

On Friday 27 February 2009 1:50:28 pm Robert Noland wrote:
> On Fri, 2009-02-27 at 12:08 -0500, John Baldwin wrote:
> > On Friday 27 February 2009 9:30:06 am Sergey G Nasonov wrote:
> > > Hello all,
> > > I have get an issue after recent kernel recompile.
> > > The problem appears after switch from X to text console and back to X11.
> > > After that vmstat -i show an  interrupt storm on cardbus device:
> > > 
> > > > vmstat -i
> > > interrupt                          total       rate
> > > irq1: atkbd0                        6483          3
> > > irq9: acpi0                         3236          1
> > > irq12: psm0                       347988        167
> > > irq14: ata0                        16431          7
> > > irq16: cbb0 uhci2+              13624982       6556
> > > irq20: uhci0                          14          0
> > > irq22: ehci0                           2          0
> > > cpu0: timer                      4154687       1999
> > > irq256: em0                        53736         25
> > > irq257: hdac0                       5797          2
> > > cpu1: timer                      4153683       1998
> > > irq258: vgapci0                   235585        113
> > > Total                           22602624      10877
> > > 
> > > I suppose that the issue related with the latest MSI interrupt 
> > > handler changes for intel graphics chipset. My laptop has i965GM.
> > > pciconf -lv:
> > > 
> > > vgapci0 at pci0:0:2:0:     class=0x030000 card=0x20b517aa chip=0x2a028086 
> > > rev=0x0c hdr=0x00
> > >     vendor     = 'Intel Corporation'
> > >     device     = 'Mobile 965 Express Integrated Graphics Controller'
> > >     class      = display
> > >     subclass   = VGA
> > > 
> > > When I added my device to drm_msi_blacklist and recompile drm modules 
the 
> > > problem disappear.
> > > Is it possible to resolve this problem without moving the device to the 
> > > drm_msi_blacklist?
> > > I can test any patches or provide additional detail if it is required.  
> > > Thanks.
> > 
> > It seems the device is still interrupting on its INTx line perhaps in 
addition 
> > to the MSI interrupts.
> 
> Hrm, I did most all of that development on a 965gm.  When you VT switch,
> the irq handler gets uninstalled and reinstalled when you return to X.
> There was an eratta on the 965gm suggesting that msi didn't work right,
> but I was never able to produce the issue.  Intel was having major
> issues with this on linux and I finally convinced them to turn msi back
> on.  My irq handler and Eric's are very similar, so I'm not sure what
> could be going on here.
> 
> There is however an issue with vblanks that might be related.  Could you
> try http://people.freebsd.org/~rnoland/drm-move_vblank_init.patch and
> see if that helps?

In this case the issue isn't that MSI isn't working I think, but that the 
hardware is sending interrupts via both routes (MSI and INTx).  If that 
happens, then you will see an interrupt storm on the INTx line, but FreeBSD 
will only notice if another device is sharing the same IRQ line.  So if your 
test machine has vgapci0 on irq 22 and you have no other devices on IRQ 22, 
then the storm would go unnoticed.  This is most likely a chip bug (unless 
the driver has to explicitly disable INTx interrupts when using MSI).  It 
would probably be a good idea to add a hw.drm.msi_enable tunable (or 
hw.drm.msi) that people can use to disable MSI perhaps.

-- 
John Baldwin