Under "heavy" RX load, the driver cannot handle the descriptors fast
enough. In detail, when a descriptor is consumed, its used flag is
cleared and once the RX budget is consumed all descriptors with a
cleared used flag are prepared to receive more data. Under load though,
the HW may constantly receive more data and use those descriptors with a
cleared used flag before they are actually prepared for next usage.

The head and tail pointers into the RX-ring should always be valid and
we can omit clearing and checking of the used flag.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Coverage data suggests that the unlikely case of receiving data while
the receive handler is running may not be that unlikely.
Coverage data after running iperf for a while:
    91320:  891:	work_done = bp->macbgem_ops.mog_rx(bp, budget);
    91320:  892:	if (work_done < budget) {
     2362:  893:		napi_complete(napi);
        -:  894:
        -:  895:		/* Packets received while interrupts were disabled */
     4724:  896:		status = macb_readl(bp, RSR);
     2362:  897:		if (unlikely(status)) {
      762:  898:			if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
      762:  899:				macb_writel(bp, ISR, MACB_BIT(RCOMP));
        -:  900:			napi_reschedule(napi);
        -:  901:		} else {
     1600:  902:			macb_writel(bp, IER, MACB_RX_INT_FLAGS);
        -:  903:		}
        -:  904:	}

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When data is received during the driver processing received data the
NAPI is re-scheduled. In that case the RX interrupt should not be
re-enabled.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

A few interrupt flags were not cleared in the ISR, resulting in a sytem
trapped in the ISR in cases one of those interrupts occurred. Clear all
flags to avoid such situations.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Just as commit "net: macb: DMA-unmap full rx-buffer"
(48330e08fa168395b9fd9f369f06cca1df204361), pass the size that
was used for mapping the memory also to the unmap routine to
avoid warnings from the DMA_API.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jeff Kirsher says:

====================
Intel Wired LAN Driver Updates

This series contains updates to e1000e only.

David provides four fixes for e1000e, first is a workaround for a hardware
erratum on 82579 devices which experienced packet loss in gigabit and 100
speeds when interconnect between the PHY and MAC is exiting K1 power saving
state.  Second expands the scope of a workaround to include i217 and i218
parts as well to address over aggressive transmit behavior when connecting
at 10Mbs half-duplex.  Next is to resolve a reported link flap issue on
82579 parts which was root caused as an interoperability problem between
82579 and at least some Broadcom PHYs in the Energy Efficient Ethernet wake
mechanism.  Lastly, restricts the workaround of putting the PHY into MDIO
slow mode to access the PHY id to relevant parts since this issue has been
fixed on the newer hardware.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

It has been determined that the workaround of putting the PHY into MDIO
slow mode to access the PHY id is not necessary with Lynx Point and newer
parts.  The issue that necessitated the workaround has been fixed on the
newer hardware.

We will maintains, as a last ditch attempt, the conversion to MDIO Slow
Mode in the failure branch when attempting to access the PHY id so as to
cover all contingencies.

Signed-off-by: Dave Ertman <davidx.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

Several customers have reported a link flap issue on 82579. The symptoms
are random and intermittent link losses when 82579 is connected to specific
link partners. Issue has been root caused as interoperability problem
between 82579 and at least some Broadcom PHYs in the Energy Efficient
Ethernet wake mechanism.

To fix the issue, we are disabling the Phase Locked Loop shutdown in 100M
Low Power Idle.  This solution will cause an increase of power in 100M EEE
link. It will cost additional 28mW in this specific mode.

Cc: Lukasz Adamczuk <lukasz.adamczuk@intel.com>
Signed-off-by: Dave Ertman <davidx.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

In commit 772d05c51c4f4896c120ad418b1e91144a2ac813 "e1000e: slow performance
between two 82579 connected via 10Mbit hub", a workaround was put into place
to address the overaggressive transmit behavior of 82579 parts when connecting
at 10Mbs half-duplex.

This same behavior is seen on i217 and i218 parts as well.  This patch expands
the original workaround to encompass these parts.

Signed-off-by: Dave Ertman <davidx.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

This is a workaround for a HW erratum on 82579 devices.
Erratum is #23 in Intel 6 Series Chipset and Intel C200 Series Chipset
specification Update June 2013.

Problem: 82579 parts experience packet loss in Gig and 100 speeds
when interconnect between PHY and MAC is exiting K1 power saving state.
This was previously believed to only affect 1Gig speed, but has been observed
at 100Mbs also.

Workaround: Disable K1 for 82579 devices at Gig and 100 speeds.

Signed-off-by: Dave Ertman <davidx.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>