net: gianfar: Implement rx_missed_errors counter

Devices with RMON support has a 16-bit RDRP counter.  It provides: "Receive
dropped packets counter. Increments for frames received which are streamed
to system but are later dropped due to lack of system resources."

To handle more than 2^16 dropped packets, a carry bit in CAR1 register is
set on overflow, so we enable irq when this is set, extending the counter
to 2^64 for handling situations where lots of packets are missed (e.g.
during heavy network storms).

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/net/ethernet/freescale/gianfar.h b/drivers/net/ethernet/freescale/gianfar.h
index c8aa140a910f..ca5e14f908fe 100644
--- a/drivers/net/ethernet/freescale/gianfar.h
+++ b/drivers/net/ethernet/freescale/gianfar.h
@@ -663,6 +663,15 @@ struct rmon_mib
 	u32	cam2;	/* 0x.73c - Carry Mask Register Two */
 };
 
+struct rmon_overflow {
+	/* lock for synchronization of the rdrp field of this struct, and
+	 * CAR1/CAR2 registers
+	 */
+	spinlock_t lock;
+	u32	imask;
+	u64	rdrp;
+};
+
 struct gfar_extra_stats {
 	atomic64_t rx_alloc_err;
 	atomic64_t rx_large;
@@ -1150,6 +1159,7 @@ struct gfar_private {
 
 	/* Network Statistics */
 	struct gfar_extra_stats extra_stats;
+	struct rmon_overflow rmon_overflow;
 
 	/* PHY stuff */
 	phy_interface_t interface;