Re: Interrupt stom on cardbus device

On Friday 27 February 2009 2:11:04 pm Robert Noland wrote:
> On Fri, 2009-02-27 at 14:03 -0500, John Baldwin wrote:
> > 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.
> 
> Ok, I do have docs on the 965, so I'll look at this.  The linux version
> does not do this, unless the OS does it in the background somewhere.

Perhaps Eric can help to answer a question about the hardware in this case.

> I thought about adding a tuneable, but I have to figure out how that
> works first... ;)

You can basically do something like this:

int drm_msi = 1;	/* Enable by default. */
TUNABLE_INT("hw.drm.msi", &drm_msi);

And later don't enable msi if it is zero.

-- 
John Baldwin