From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: powerpc/cell/axon-msi: fix MSI after kexec From: Michael Ellerman To: Arnd Bergmann In-Reply-To: <200812122019.51191.arnd@arndb.de> References: <200812122019.51191.arnd@arndb.de> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-5t6+J21KYP4+mZ/i3Vd7" Date: Mon, 15 Dec 2008 15:30:26 +1100 Message-Id: <1229315426.7118.59.camel@localhost> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, cbe-oss-dev@ozlabs.org Reply-To: michael@ellerman.id.au List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-5t6+J21KYP4+mZ/i3Vd7 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Fri, 2008-12-12 at 20:19 +0100, Arnd Bergmann wrote: > Commit d015fe995 'powerpc/cell/axon-msi: Retry on missing interrupt' > has turned a rare failure to kexec on QS22 into a reproducible > error, which we have now analysed. >=20 > The problem is that after a kexec, the MSIC hardware still points > into the middle of the old ring buffer. We set up the ring buffer > during reboot, but not the offset into it. On older kernels, this > would cause a storm of thousands of spurious interrupts after a > kexec, which would most of the time get dropped silently. >=20 > With the new code, we time out on each interrupt, waiting for > it to become valid. If more interrupts come in that we time > out on, this goes on indefinitely, which eventually leads to > a hard crash. >=20 > The solution in this patch is to read the current offset from > the MSIC when reinitializing it. This now works correctly, as > expected. >=20 > Reported-by: Dirk Herrendoerfer > Signed-off-by: Arnd Bergmann > --- >=20 > Please apply when Dirk and Michael have given their Ack. > Should we have it in 2.6.28? Not sure if going from 'works sometimes' > to 'works never' counts as a regression. Most users won't be impacted, > because they don't use kexec on QS22. I think it does count, it's a pretty small fix. > diff --git a/arch/powerpc/platforms/cell/axon_msi.c b/arch/powerpc/platfo= rms/cell/axon_msi.c > index 442cf36..548fa4e 100644 > --- a/arch/powerpc/platforms/cell/axon_msi.c > +++ b/arch/powerpc/platforms/cell/axon_msi.c > @@ -413,6 +422,9 @@ static int axon_msi_probe(struct of_device *device, > MSIC_CTRL_IRQ_ENABLE | MSIC_CTRL_ENABLE | > MSIC_CTRL_FIFO_SIZE); > =20 > + msic->read_offset =3D dcr_read(msic->dcr_host, MSIC_WRITE_OFFSET_REG) > + & MSIC_FIFO_SIZE_MASK; > + Acked-by: Michael Ellerman cheers --=20 Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person --=-5t6+J21KYP4+mZ/i3Vd7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAklF3WIACgkQdSjSd0sB4dJtqwCfVUSN0oEygcqP8MJwAWoFIxSJ XToAoJpswxgEzd4fzo/uc7b8CrTrvmPw =Fyfl -----END PGP SIGNATURE----- --=-5t6+J21KYP4+mZ/i3Vd7--