firewire: net: Use posted writes

Change memory region to ohci "middle address space". This effectively
reduces the number of packets by 50%.

[Stefan R.:]  This eliminates 1394 ack packets and improved throughput
by a few percent in some tests with an S400a connection with and without
gap count optimization.  Since firewire-net taxes the AR-req DMA unit of
a FireWire controller much more than firewire-sbp2 (which uses the
middle address space with PCI posted writes too), this commit also
changes a related error printk into a ratelimited one as a precaution.

Side note:  The IPv4-over-1394 drivers of Mac OS X 10.4, Windows XP SP3,
and the Thesycon 1394 bus driver for Windows all use the middle address
space too.

Signed-off-by: Stephan Gatzka <stephan@gatzka.org>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/net.c

@@ -1121,17 +1121,12 @@ static int fwnet_broadcast_start(struct fwnet_device *dev)
 	unsigned u;
 
 	if (dev->local_fifo == FWNET_NO_FIFO_ADDR) {
-		/* outside OHCI posted write area? */
-		static const struct fw_address_region region = {
-			.start = 0xffff00000000ULL,
-			.end   = CSR_REGISTER_BASE,
-		};
-
 		dev->handler.length = 4096;
 		dev->handler.address_callback = fwnet_receive_packet;
 		dev->handler.callback_data = dev;
 
-		retval = fw_core_add_address_handler(&dev->handler, &region);
+		retval = fw_core_add_address_handler(&dev->handler,
+					&fw_high_memory_region);
 		if (retval < 0)
 			goto failed_initial;
 

drivers/firewire/ohci.c

@@ -2045,7 +2045,8 @@ static irqreturn_t irq_handler(int irq, void *data)
 		reg_read(ohci, OHCI1394_PostedWriteAddressLo);
 		reg_write(ohci, OHCI1394_IntEventClear,
 			  OHCI1394_postedWriteErr);
-		fw_error("PCI posted write error\n");
+		if (printk_ratelimit())
+			fw_error("PCI posted write error\n");
 	}
 
 	if (unlikely(event & OHCI1394_cycleTooLong)) {