netdev - Re: [PATCH net] skge: dma_sync the whole receive buffer

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Date:	Thu, 15 Aug 2013 08:41:17 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	poma <pomidorabelisima@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net] skge: dma_sync the whole receive buffer

On Wed, 14 Aug 2013 20:29:06 +0200
poma <pomidorabelisima@...il.com> wrote:

> On 14.08.2013 18:20, Stephen Hemminger wrote:
> > On Wed, 14 Aug 2013 12:20:03 +0200
> > poma <pomidorabelisima@...il.com> wrote:
> > 
> >> On 14.08.2013 03:00, Stephen Hemminger wrote:
> >>> On Tue, 13 Aug 2013 15:09:55 -0700 (PDT)
> >>> David Miller <davem@...emloft.net> wrote:
> >>>
> >>>> From: Stephen Hemminger <stephen@...workplumber.org>
> >>>> Date: Sat, 10 Aug 2013 15:02:07 -0700
> >>>>
> >>>>> The DMA sync should sync the whole receive buffer, not just
> >>>>> part of it. Fixes log messages dma_sync_check.
> >>>>>
> >>>>> Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> >>>>
> >>>> Applied, but I really suspect that your "check DMA mapping errors"
> >>>> patch has added a serious regression.  A regression much worse than
> >>>> the bug you were trying to fix with that change.
> >>>
> >>> Argh. The problem is deeper than that. Device got broken somewhere between
> >>> 3.2 and 3.4. My old Dlink card works on 3.2 but gets DMA errors on 3.4.
> >>> The config's are different though so checking that as well.
> >>>
> >>
> >> Can I help you with debugging?
> >> DGE-530T is rather solid device.
> > 
> > Don't think it is a hardware problem.
> > The failure is when the board access the Receive ring PCI memory area.
> > This region is allocated with pci_alloc_consistent and therefore should
> > be available. Two possible issues are driver math issues, or hardware
> > problems with where the region is located. Some of these cards don't
> > really have full 64 bit PCI support.
> > 
> > My board is:
> > 05:01.0 Ethernet controller: D-Link System Inc Gigabit Ethernet Adapter (rev 11)
> > 	Subsystem: D-Link System Inc DGE-530T Gigabit Ethernet Adapter
> > 	Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 18
> > 	Memory at f7d20000 (32-bit, non-prefetchable) [size=16K]
> > 	I/O ports at c000 [size=256]
> > 	Expansion ROM at f7d00000 [disabled] [size=128K]
> > 	Capabilities: [48] Power Management version 2
> > 	Capabilities: [50] Vital Product Data
> > 	Kernel driver in use: skge
> > 
> > 
> > What is your config?
> > 
> 
> 01:09.0 Ethernet controller: D-Link System Inc Gigabit Ethernet Adapter
> (rev 11)
> 	Subsystem: D-Link System Inc DGE-530T Gigabit Ethernet Adapter
> 	Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 19
> 	Memory at fbffc000 (32-bit, non-prefetchable) [size=16K]
> 	I/O ports at b400 [size=256]
> 	[virtual] Expansion ROM at ec000000 [disabled] [size=128K]
> 	Capabilities: [48] Power Management version 2
> 	Capabilities: [50] Vital Product Data
> 	Kernel driver in use: skge
> 
> 
> poma
> 

In the course of debugging this, I moved the card to another slot
and all the problems went away. I suspect either card insertion or more likely
the crap consumer motherboards don't have full PCI support on some slots.

There doesn't seem to be anyway to address this in software.
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