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

[Alexey Brodkin]

DW GMAC on ARC SDP boards doesn't enter promiscuous mode if
Ethernet PHY haven't got established link. Good examples are
auto-negotiation in progress or disconnected cable.

We do see Linux kernel sets GMAC's MAC filter register
properly but GMAC's hardware doesn't accept new settings.

We believe it is a hardware issue, most probably problem of
integration of DW GMAC and PHY on the board.

As a work-around we completely disable frame filtering
in GMAC hardware (once and for good) which forces GMAC to enter
promiscuous mode with the first write to MAC filter register.
That gives us working bridge that consists of eth0 and wlan0
(USB Wi-Fi dongle). I.e. we finally have working "Dumb AP" setup made
of ARC AXS10x boards.

Given that hack is quite dirty (in loaded wired networks this will
effectively load CPU with junk packets even if user doesn't need promisc
mode) and there's no indication any other boards with DW GMAC suffer
from the same issue we're patching only kernel for ARC boards.

Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
Cc: John Crispin <john at phrozen.org>,
Cc: Felix Fietkau <nbd at nbd.name>
---

Since initial post of the patch we made quite a lot of work trying to
figure out what happens here and with enough evidence may claim now faulty
integration of GMAC & PHY. Given there's no way for us to fix hardware
we believe work-around in kernel driver makes perfect sense now.

 ...-stmmac-Disable-fame-filtering-completely.patch | 36 ++++++++++++++++++++++
 ...-stmmac-Disable-fame-filtering-completely.patch | 36 ++++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 target/linux/arc770/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch
 create mode 100644 target/linux/archs38/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch

diff --git a/target/linux/arc770/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch b/target/linux/arc770/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch
new file mode 100644
index 0000000..d47f155
--- /dev/null
+++ b/target/linux/arc770/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch
@@ -0,0 +1,36 @@
+From 0031b9011cb2b2b1de4dbb4f9620303aec760db4 Mon Sep 17 00:00:00 2001
+From: Alexey Brodkin <abrodkin at synopsys.com>
+Date: Wed, 27 Jul 2016 11:33:14 +0300
+Subject: [PATCH] stmmac: Disable fame filtering completely
+
+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).
+
+As a work-around we completely disable frame filtering
+in GMAC hardware which gives us working bridge that consists
+of eth0 and wlan0 (USB Wi-Fi dongle). I.e. we finally have
+working "Dumb AP" setup made of ARC AXS10x boards.
+
+Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
+---
+ drivers/net/ethernet/stmicro/stmmac/common.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
+index 623c6ed..6396b81 100644
+--- a/drivers/net/ethernet/stmicro/stmmac/common.h
++++ b/drivers/net/ethernet/stmicro/stmmac/common.h
+@@ -42,7 +42,7 @@
+ #define	DWMAC_CORE_3_50	0x35
+ 
+ #undef FRAME_FILTER_DEBUG
+-/* #define FRAME_FILTER_DEBUG */
++#define FRAME_FILTER_DEBUG
+ 
+ /* Extra statistic and debug information exposed by ethtool */
+ struct stmmac_extra_stats {
+-- 
+2.7.4
+
diff --git a/target/linux/archs38/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch b/target/linux/archs38/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch
new file mode 100644
index 0000000..d47f155
--- /dev/null
+++ b/target/linux/archs38/patches-4.4/700-stmmac-Disable-fame-filtering-completely.patch
@@ -0,0 +1,36 @@
+From 0031b9011cb2b2b1de4dbb4f9620303aec760db4 Mon Sep 17 00:00:00 2001
+From: Alexey Brodkin <abrodkin at synopsys.com>
+Date: Wed, 27 Jul 2016 11:33:14 +0300
+Subject: [PATCH] stmmac: Disable fame filtering completely
+
+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).
+
+As a work-around we completely disable frame filtering
+in GMAC hardware which gives us working bridge that consists
+of eth0 and wlan0 (USB Wi-Fi dongle). I.e. we finally have
+working "Dumb AP" setup made of ARC AXS10x boards.
+
+Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
+---
+ drivers/net/ethernet/stmicro/stmmac/common.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
+index 623c6ed..6396b81 100644
+--- a/drivers/net/ethernet/stmicro/stmmac/common.h
++++ b/drivers/net/ethernet/stmicro/stmmac/common.h
+@@ -42,7 +42,7 @@
+ #define	DWMAC_CORE_3_50	0x35
+ 
+ #undef FRAME_FILTER_DEBUG
+-/* #define FRAME_FILTER_DEBUG */
++#define FRAME_FILTER_DEBUG
+ 
+ /* Extra statistic and debug information exposed by ethtool */
+ struct stmmac_extra_stats {
+-- 
+2.7.4
+
-- 
2.7.4