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Date:      Fri, 27 Feb 2009 19:35:59 -0600
From:      Robert Noland <rnoland@FreeBSD.org>
To:        John Baldwin <jhb@freebsd.org>
Cc:        freebsd-current@freebsd.org, Sergey G Nasonov <snasonov@bcc.ru>
Subject:   Re: Interrupt stom on cardbus device
Message-ID:  <1235784959.1289.67.camel@widget.2hip.net>
In-Reply-To: <200902271502.37051.jhb@freebsd.org>
References:  <200902271730.07660.snasonov@bcc.ru> <200902271403.46828.jhb@freebsd.org> <1235761864.1289.54.camel@widget.2hip.net> <200902271502.37051.jhb@freebsd.org>

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On Fri, 2009-02-27 at 15:02 -0500, John Baldwin wrote:
> 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 bac=
k to X11.
> > > > > > After that vmstat -i show an  interrupt storm on cardbus device=
:
> > > > > >=20
> > > > > > > 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
> > > > > >=20
> > > > > > I suppose that the issue related with the latest MSI interrupt=20
> > > > > > handler changes for intel graphics chipset. My laptop has i965G=
M.
> > > > > > pciconf -lv:
> > > > > >=20
> > > > > > vgapci0@pci0:0:2:0:     class=3D0x030000 card=3D0x20b517aa chip=
=3D0x2a028086=20
> > > > > > rev=3D0x0c hdr=3D0x00
> > > > > >     vendor     =3D 'Intel Corporation'
> > > > > >     device     =3D 'Mobile 965 Express Integrated Graphics Cont=
roller'
> > > > > >     class      =3D display
> > > > > >     subclass   =3D VGA
> > > > > >=20
> > > > > > When I added my device to drm_msi_blacklist and recompile drm m=
odules=20
> > > the=20
> > > > > > problem disappear.
> > > > > > Is it possible to resolve this problem without moving the devic=
e to the=20
> > > > > > drm_msi_blacklist?
> > > > > > I can test any patches or provide additional detail if it is re=
quired. =20
> > > > > > Thanks.
> > > > >=20
> > > > > It seems the device is still interrupting on its INTx line perhap=
s in=20
> > > addition=20
> > > > > to the MSI interrupts.
> > > >=20
> > > > Hrm, I did most all of that development on a 965gm.  When you VT sw=
itch,
> > > > 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 ri=
ght,
> > > > 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 wh=
at
> > > > could be going on here.
> > > >=20
> > > > There is however an issue with vblanks that might be related.  Coul=
d you
> > > > try http://people.freebsd.org/~rnoland/drm-move_vblank_init.patch a=
nd
> > > > see if that helps?
> > >=20
> > > In this case the issue isn't that MSI isn't working I think, but that=
 the=20
> > > hardware is sending interrupts via both routes (MSI and INTx).  If th=
at=20
> > > happens, then you will see an interrupt storm on the INTx line, but F=
reeBSD=20
> > > will only notice if another device is sharing the same IRQ line.  So =
if your=20
> > > test machine has vgapci0 on irq 22 and you have no other devices on I=
RQ 22,=20
> > > then the storm would go unnoticed.  This is most likely a chip bug (u=
nless=20
> > > the driver has to explicitly disable INTx interrupts when using MSI).=
  It=20
> > > would probably be a good idea to add a hw.drm.msi_enable tunable (or=20
> > > hw.drm.msi) that people can use to disable MSI perhaps.
> >=20
> > 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.

Ok, so I looked over the 965 docs again and noticed PCIR_COMMAND bit 10.
Then I pulled up the AMD docs on their PCIE cards and they also have
this bit.  I made an test patch for just the i915 driver to ensure that
this fixes the issue, but it seems like a more general fix is in order.
I'm proposing to disable INTx when we setup MSI/MSIX interrupts.  I
talked with scottl@ about this a bit last night and this seems like the
right thing to do, or at least it shouldn't hurt much...

John, what do you think of the attached patch?

robert.

> Perhaps Eric can help to answer a question about the hardware in this cas=
e.
>=20
> > I thought about adding a tuneable, but I have to figure out how that
> > works first... ;)
>=20
> You can basically do something like this:
>=20
> int drm_msi =3D 1;	/* Enable by default. */
> TUNABLE_INT("hw.drm.msi", &drm_msi);
>=20
> And later don't enable msi if it is zero.
>=20
--=20
Robert Noland <rnoland@FreeBSD.org>
FreeBSD

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