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

[Alexey Brodkin]

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.

And I do think in the meantime it's good to apply this patch so people
get working Wireless AP without extra patching of sources or what's even
better with snapshot images.

-Alexey