[LEDE-DEV] [PATCH] linux/arc*: disable MAC frame filter in DW GMAC

[Alexey Brodkin]

Hi Daniel,

On Tue, 2016-08-16 at 17:12 +0200, Daniel Golle wrote:
> Hi Alexey,
> 
> On Tue, Aug 16, 2016 at 06:06:20AM +0000, Alexey Brodkin wrote:
> > 
> > Hi Felix,
> > 
> > On Wed, 2016-07-27 at 17:19 +0200, Felix Fietkau wrote:
> > > 
> > > On 2016-07-27 14:11, Alexey Brodkin wrote:
> > > > 
> > > > 
> > > > For some [still unknown] reason in ARC SDP boards
> > > > DW GMAC doesn't enter promiscuous mode if eth0 gets
> > > > added to the br-lan interface before Ethernet PHY finishes
> > > > autonegotiation (PHY gets reset on DW GMAC start).
> > > 
> > > I think this is something we need to look at more closely instead of
> > > just papering over it in this way. By the way, arc* aren't the only ones
> > > using stmmac, ipq806x uses it as well and might be equally affected.
> > > Did you check if the network stack tells the driver to go into promisc
> > > mode? Or does the frame filtering registers simply get clobbered
> > > somewhere internally?
> > > 
> > > Let's do some more testing and get this fixed properly...
> > 
> > So I spent quite some time with that, short summary could be found here:
> > http://lists.infradead.org/pipermail/linux-snps-arc/2016-August/001395.html
> > 
> > Probably most important summary for us here is:
> > ------------------------->8--------------------------
> > Unfortunately I cannot figure out why GMAC behaves that way.
> > As per GMAC's databook the only reason for it to not react on a register
> > being written is missing input clock but there's no reason for the
> > clock to be missing and I don't seem to have a way to check if there's
> > a problem with clock or not.
> > ------------------------->8--------------------------
> > 
> > It worth trying on other boards with DW GMAC but the only other board
> > except ARC SDP ones is Cubieboard2 with sunxi-gmac (which is a kind of
> > DW GMAC as I may see from its Linux's driver) but on CB2 all works as
> > exected. If somebody wants to volunteer I'll be more than happy to work
> > with him/her trying to get more datapoints.
> 
> stmac/dwmac works as expected on Oxford/PLXTECH OX82x/NAS782x (oxnas
> target on OpenWrt/LEDE) as well.

That's good to know but remember what was my use-case to reproduce the
problem in questions - DW GMAC must be put in promisq mode while PHY
has no link established (the simplest option is to unplug the cable).

Have you tried exactly that scenario?

-Alexey