DMA remote memcpy requests

[Jan.Glauber@cavium.com (Jan Glauber)]

On Mon, Oct 22, 2018 at 02:39:00PM +0000, Adam Cottrel wrote:
> Dear Jan,
> 
> As I understand this, to turn off I need to re-compile without SMMU driver support via the kernel config flags.
> 
> However, if I turn the SMU off, how will the system cope?

The SMMU should be optional, but I didn't try it myselfs so bad things
might happen...

Regards,
Jan

> Best,
> Adam
> 
> > -----Original Message-----
> > From: Jan Glauber <Jan.Glauber@cavium.com>
> > Sent: 22 October 2018 15:29
> > To: Adam Cottrel <adam.cottrel@veea.com>
> > Cc: Nair, Jayachandran <Jayachandran.Nair@cavium.com>; rric at kernel.org;
> > Goutham, Sunil <Sunil.Goutham@cavium.com>; Will Deacon
> > <will.deacon@arm.com>; Robin Murphy <robin.murphy@arm.com>; linux-
> > arm-kernel at lists.infradead.org
> > Subject: Re: DMA remote memcpy requests
> >
> > On Thu, Oct 18, 2018 at 03:36:25PM +0000, Adam Cottrel wrote:
> > > Dear Jan,
> > >
> > > Sorry for the delay in getting back to you - the patch took longer than
> > expected to finish.
> > >
> > >  $ cat /proc/config.gz | gunzip | grep ERRATUM
> > > CONFIG_ARM64_ERRATUM_826319=y
> > CONFIG_ARM64_ERRATUM_827319=y
> > > CONFIG_ARM64_ERRATUM_824069=y
> > CONFIG_ARM64_ERRATUM_819472=y
> > > CONFIG_ARM64_ERRATUM_832075=y
> > CONFIG_ARM64_ERRATUM_834220=y
> > > CONFIG_ARM64_ERRATUM_845719=y
> > CONFIG_ARM64_ERRATUM_843419=y
> > > CONFIG_CAVIUM_ERRATUM_22375=y
> > CONFIG_CAVIUM_ERRATUM_23144=y
> > > CONFIG_CAVIUM_ERRATUM_23154=y
> > CONFIG_CAVIUM_ERRATUM_27456=y
> > > CONFIG_CAVIUM_ERRATUM_28168=y                               <---------------------
> > HERE!!
> > > CONFIG_CAVIUM_ERRATUM_30115=y
> > > CONFIG_QCOM_FALKOR_ERRATUM_1003=y
> > > CONFIG_QCOM_FALKOR_ERRATUM_1009=y
> > > CONFIG_QCOM_QDF2400_ERRATUM_0065=y
> > > CONFIG_FSL_ERRATUM_A008585=y
> > > CONFIG_HISILICON_ERRATUM_161010101=y
> > > CONFIG_ARM64_ERRATUM_858921=y
> > >
> > > As you can see, the fix is enabled, but when I test, it is not making any
> > difference to the original issue. The ath10k driver is still dropping inward DMA
> > under memory pressure.
> >
> > OK, it was just a guess from my side.
> >
> > > As an aside, I had to make one small change to the patch due to differences
> > between earlier kernel versions. Please see cavium.diff attached. Is this an
> > acceptable change?
> >
> > Your resolution looks fine.
> >
> > > Before we discount this as being a fix, please can you tell me how I can
> > prove that the patch is actually working on my platform?
> >
> > It looks like it doesn't solve your issue. I just wanted to rule this one out.
> >
> > Have you tried the other suggestion of completely turning of the SMMU?
> >
> > Regards,
> > Jan
> >
> >
> > > Best,
> > > Adam
> > >
> > > > -----Original Message-----
> > > > From: linux-arm-kernel
> > > > <linux-arm-kernel-bounces@lists.infradead.org> On Behalf Of Adam
> > > > Cottrel
> > > > Sent: 15 October 2018 16:51
> > > > To: Jan Glauber <Jan.Glauber@cavium.com>
> > > > Cc: Nair, Jayachandran <Jayachandran.Nair@cavium.com>;
> > > > rric at kernel.org; Goutham, Sunil <Sunil.Goutham@cavium.com>; Will
> > > > Deacon <will.deacon@arm.com>; Robin Murphy
> > <robin.murphy@arm.com>;
> > > > linux- arm-kernel at lists.infradead.org
> > > > Subject: RE: DMA remote memcpy requests
> > > >
> > > > Dear Jan,
> > > >
> > > > > I'm not sure where that point would be where DMA request could be
> > > > > lost here.
> > > > > The MMC and PCIe only meet in the NCB (near coprocessor bus) which
> > > > > goes to the Coherent memory interconnect and L2 cache.
> > > > >
> > > > > I've looked for any known errata but didn't find anything that
> > > > > would match your problem.
> > > >
> > > > For the purposes of debug, is it possible for me to turn off the
> > > > MMC? Or the
> > > > L2 cache? Or put it into pass through mode? Or get any kind of stack
> > > > trace on its operation?
> > > >
> > > > Best,
> > > > Adam
> > > >
> > > > _______________________________________________
> > > > linux-arm-kernel mailing list
> > > > linux-arm-kernel at lists.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >