3c59x.c

/* EtherLinkXL.c: A 3Com EtherLink PCI III/XL ethernet driver for linux. */
/*
	Written 1996-1999 by Donald Becker.

	This software may be used and distributed according to the terms
	of the GNU General Public License, incorporated herein by reference.

	This driver is for the 3Com "Vortex" and "Boomerang" series ethercards.
	Members of the series include Fast EtherLink 3c590/3c592/3c595/3c597
	and the EtherLink XL 3c900 and 3c905 cards.

	Problem reports and questions should be directed to
	vortex@scyld.com

	The author may be reached as becker@scyld.com, or C/O
	Scyld Computing Corporation
	410 Severn Ave., Suite 210
	Annapolis MD 21403

*/

/*
 * FIXME: This driver _could_ support MTU changing, but doesn't.  See Don's hamachi.c implementation
 * as well as other drivers
 *
 * NOTE: If you make 'vortex_debug' a constant (#define vortex_debug 0) the driver shrinks by 2k
 * due to dead code elimination.  There will be some performance benefits from this due to
 * elimination of all the tests and reduced cache footprint.
 */


#define DRV_NAME	"3c59x"



/* A few values that may be tweaked. */
/* Keep the ring sizes a power of two for efficiency. */
#define TX_RING_SIZE	16
#define RX_RING_SIZE	32
#define PKT_BUF_SZ		1536			/* Size of each temporary Rx buffer.*/

/* "Knobs" that adjust features and parameters. */
/* Set the copy breakpoint for the copy-only-tiny-frames scheme.
   Setting to > 1512 effectively disables this feature. */
#ifndef __arm__
static int rx_copybreak = 200;
#else
/* ARM systems perform better by disregarding the bus-master
   transfer capability of these cards. -- rmk */
static int rx_copybreak = 1513;
#endif
/* Allow setting MTU to a larger size, bypassing the normal ethernet setup. */
static const int mtu = 1500;
/* Maximum events (Rx packets, etc.) to handle at each interrupt. */
static int max_interrupt_work = 32;
/* Tx timeout interval (millisecs) */
static int watchdog = 5000;

/* Allow aggregation of Tx interrupts.  Saves CPU load at the cost
 * of possible Tx stalls if the system is blocking interrupts
 * somewhere else.  Undefine this to disable.
 */
#define tx_interrupt_mitigation 1

/* Put out somewhat more debugging messages. (0: no msg, 1 minimal .. 6). */
#define vortex_debug debug
#ifdef VORTEX_DEBUG
static int vortex_debug = VORTEX_DEBUG;
#else
static int vortex_debug = 1;
#endif

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/pci.h>
#include <linux/mii.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <linux/highmem.h>
#include <linux/eisa.h>
#include <linux/bitops.h>
#include <linux/jiffies.h>
#include <asm/irq.h>			/* For nr_irqs only. */
#include <asm/io.h>
#include <asm/uaccess.h>

/* Kernel compatibility defines, some common to David Hinds' PCMCIA package.
   This is only in the support-all-kernels source code. */

#define RUN_AT(x) (jiffies + (x))

#include <linux/delay.h>


static const char version[] __devinitconst =
	DRV_NAME ": Donald Becker and others.\n";

MODULE_AUTHOR("Donald Becker <becker@scyld.com>");
MODULE_DESCRIPTION("3Com 3c59x/3c9xx ethernet driver ");
MODULE_LICENSE("GPL");


/* Operational parameter that usually are not changed. */

/* The Vortex size is twice that of the original EtherLinkIII series: the
   runtime register window, window 1, is now always mapped in.
   The Boomerang size is twice as large as the Vortex -- it has additional
   bus master control registers. */
#define VORTEX_TOTAL_SIZE 0x20
#define BOOMERANG_TOTAL_SIZE 0x40

/* Set iff a MII transceiver on any interface requires mdio preamble.
   This only set with the original DP83840 on older 3c905 boards, so the extra
   code size of a per-interface flag is not worthwhile. */
static char mii_preamble_required;

#define PFX DRV_NAME ": "



/*
				Theory of Operation

I. Board Compatibility

This device driver is designed for the 3Com FastEtherLink and FastEtherLink
XL, 3Com's PCI to 10/100baseT adapters.  It also works with the 10Mbs
versions of the FastEtherLink cards.  The supported product IDs are
  3c590, 3c592, 3c595, 3c597, 3c900, 3c905

The related ISA 3c515 is supported with a separate driver, 3c515.c, included
with the kernel source or available from
    cesdis.gsfc.nasa.gov:/pub/linux/drivers/3c515.html

II. Board-specific settings

PCI bus devices are configured by the system at boot time, so no jumpers
need to be set on the board.  The system BIOS should be set to assign the
PCI INTA signal to an otherwise unused system IRQ line.

The EEPROM settings for media type and forced-full-duplex are observed.
The EEPROM media type should be left at the default "autoselect" unless using
10base2 or AUI connections which cannot be reliably detected.

III. Driver operation

The 3c59x series use an interface that's very similar to the previous 3c5x9
series.  The primary interface is two programmed-I/O FIFOs, with an
alternate single-contiguous-region bus-master transfer (see next).

The 3c900 "Boomerang" series uses a full-bus-master interface with separate
lists of transmit and receive descriptors, similar to the AMD LANCE/PCnet,
DEC Tulip and Intel Speedo3.  The first chip version retains a compatible
programmed-I/O interface that has been removed in 'B' and subsequent board
revisions.

One extension that is advertised in a very large font is that the adapters
are capable of being bus masters.  On the Vortex chip this capability was
only for a single contiguous region making it far less useful than the full
bus master capability.  There is a significant performance impact of taking
an extra interrupt or polling for the completion of each transfer, as well
as difficulty sharing the single transfer engine between the transmit and
receive threads.  Using DMA transfers is a win only with large blocks or
with the flawed versions of the Intel Orion motherboard PCI controller.

The Boomerang chip's full-bus-master interface is useful, and has the
currently-unused advantages over other similar chips that queued transmit
packets may be reordered and receive buffer groups are associated with a
single frame.

With full-bus-master support, this driver uses a "RX_COPYBREAK" scheme.
Rather than a fixed intermediate receive buffer, this scheme allocates
full-sized skbuffs as receive buffers.  The value RX_COPYBREAK is used as
the copying breakpoint: it is chosen to trade-off the memory wasted by
passing the full-sized skbuff to the queue layer for all frames vs. the
copying cost of copying a frame to a correctly-sized skbuff.

IIIC. Synchronization
The driver runs as two independent, single-threaded flows of control.  One
is the send-packet routine, which enforces single-threaded use by the
dev->tbusy flag.  The other thread is the interrupt handler, which is single
threaded by the hardware and other software.

IV. Notes

Thanks to Cameron Spitzer and Terry Murphy of 3Com for providing development
3c590, 3c595, and 3c900 boards.
The name "Vortex" is the internal 3Com project name for the PCI ASIC, and
the EISA version is called "Demon".  According to Terry these names come
from rides at the local amusement park.