Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

Pull another networking update from David Miller:
 "Small follow-up to the main merge pull from the other day:

  1) Alexander Duyck's DMA memory barrier patch set.

  2) cxgb4 driver fixes from Karen Xie.

  3) Add missing export of fixed_phy_register() to modules, from Mark
     Salter.

  4) DSA bug fixes from Florian Fainelli"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (24 commits)
  net/macb: add TX multiqueue support for gem
  linux/interrupt.h: remove the definition of unused tasklet_hi_enable
  jme: replace calls to redundant function
  net: ethernet: davicom: Allow to select DM9000 for nios2
  net: ethernet: smsc: Allow to select SMC91X for nios2
  cxgb4: Add support for QSA modules
  libcxgbi: fix freeing skb prematurely
  cxgb4i: use set_wr_txq() to set tx queues
  cxgb4i: handle non-pdu-aligned rx data
  cxgb4i: additional types of negative advice
  cxgb4/cxgb4i: set the max. pdu length in firmware
  cxgb4i: fix credit check for tx_data_wr
  cxgb4i: fix tx immediate data credit check
  net: phy: export fixed_phy_register()
  fib_trie: Fix trie balancing issue if new node pushes down existing node
  vlan: Add ability to always enable TSO/UFO
  r8169:update rtl8168g pcie ephy parameter
  net: dsa: bcm_sf2: force link for all fixed PHY devices
  fm10k/igb/ixgbe: Use dma_rmb on Rx descriptor reads
  r8169: Use dma_rmb() and dma_wmb() for DescOwn checks
  ...

1 files changed, 42 insertions, 0 deletions

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 7ee2ae6d5451..70a09f8a0383 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1633,6 +1633,48 @@ There are some more advanced barrier functions:
      operations" subsection for information on where to use these.
 
 
+ (*) dma_wmb();
+ (*) dma_rmb();
+
+     These are for use with consistent memory to guarantee the ordering
+     of writes or reads of shared memory accessible to both the CPU and a
+     DMA capable device.
+
+     For example, consider a device driver that shares memory with a device
+     and uses a descriptor status value to indicate if the descriptor belongs
+     to the device or the CPU, and a doorbell to notify it when new
+     descriptors are available:
+
+	if (desc->status != DEVICE_OWN) {
+		/* do not read data until we own descriptor */
+		dma_rmb();
+
+		/* read/modify data */
+		read_data = desc->data;
+		desc->data = write_data;
+
+		/* flush modifications before status update */
+		dma_wmb();
+
+		/* assign ownership */
+		desc->status = DEVICE_OWN;
+
+		/* force memory to sync before notifying device via MMIO */
+		wmb();
+
+		/* notify device of new descriptors */
+		writel(DESC_NOTIFY, doorbell);
+	}
+
+     The dma_rmb() allows us guarantee the device has released ownership
+     before we read the data from the descriptor, and he dma_wmb() allows
+     us to guarantee the data is written to the descriptor before the device
+     can see it now has ownership.  The wmb() is needed to guarantee that the
+     cache coherent memory writes have completed before attempting a write to
+     the cache incoherent MMIO region.
+
+     See Documentation/DMA-API.txt for more information on consistent memory.
+
 MMIO WRITE BARRIER
 ------------------