DMA remote memcpy requests

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

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