1 Tulip Ethernet Card Driver
2 Maintained by Jeff Garzik <jgarzik@mandrakesoft.com>
3
4 The Tulip driver was developed by Donald Becker and changed by
5 Takashi Manabe and a cast of thousands.
6
7 For 2.4.x and later kernels, the Linux Tulip driver is available at
8 http://sourceforge.net/projects/tulip/
9
10 This driver is for the Digital "Tulip" Ethernet adapter interface.
11 It should work with most DEC 21*4*-based chips/ethercards, as well as
12 with work-alike chips from Lite-On (PNIC) and Macronix (MXIC) and ASIX.
13
14 The author may be reached as becker@scyld.com, or C/O
15 Center of Excellence in Space Data and Information Sciences
16 Code 930.5, Goddard Space Flight Center, Greenbelt MD 20771
17
18 Additional information on Donald Becker's tulip.c
19 is available at http://www.scyld.com/network/tulip.html
20
21
22
23
24 Theory of Operation
25
26 Board Compatibility
27 ===================
28
29 This device driver is designed for the DECchip "Tulip", Digital's
30 single-chip ethernet controllers for PCI. Supported members of the family
31 are the 21040, 21041, 21140, 21140A, 21142, and 21143. Similar work-alike
32 chips from Lite-On, Macronics, ASIX, Compex and other listed below are also
33 supported.
34
35 These chips are used on at least 140 unique PCI board designs. The great
36 number of chips and board designs supported is the reason for the
37 driver size and complexity. Almost of the increasing complexity is in the
38 board configuration and media selection code. There is very little
39 increasing in the operational critical path length.
40
41 Board-specific settings
42 =======================
43
44 PCI bus devices are configured by the system at boot time, so no jumpers
45 need to be set on the board. The system BIOS preferably should assign the
46 PCI INTA signal to an otherwise unused system IRQ line.
47
48 Some boards have EEPROMs tables with default media entry. The factory default
49 is usually "autoselect". This should only be overridden when using
50 transceiver connections without link beat e.g. 10base2 or AUI, or (rarely!)
51 for forcing full-duplex when used with old link partners that do not do
52 autonegotiation.
53
54 Driver operation
55 ================
56
57 Ring buffers
58 ------------
59
60 The Tulip can use either ring buffers or lists of Tx and Rx descriptors.
61 This driver uses statically allocated rings of Rx and Tx descriptors, set at
62 compile time by RX/TX_RING_SIZE. This version of the driver allocates skbuffs
63 for the Rx ring buffers at open() time and passes the skb->data field to the
64 Tulip as receive data buffers. When an incoming frame is less than
65 RX_COPYBREAK bytes long, a fresh skbuff is allocated and the frame is
66 copied to the new skbuff. When the incoming frame is larger, the skbuff is
67 passed directly up the protocol stack and replaced by a newly allocated
68 skbuff.
69
70 The RX_COPYBREAK value is chosen to trade-off the memory wasted by
71 using a full-sized skbuff for small frames vs. the copying costs of larger
72 frames. For small frames the copying cost is negligible (esp. considering
73 that we are pre-loading the cache with immediately useful header
74 information). For large frames the copying cost is non-trivial, and the
75 larger copy might flush the cache of useful data. A subtle aspect of this
76 choice is that the Tulip only receives into longword aligned buffers, thus
77 the IP header at offset 14 isn't longword aligned for further processing.
78 Copied frames are put into the new skbuff at an offset of "+2", thus copying
79 has the beneficial effect of aligning the IP header and preloading the
80 cache.
81
82 Synchronization
83 ---------------
84 The driver runs as two independent, single-threaded flows of control. One
85 is the send-packet routine, which enforces single-threaded use by the
86 dev->tbusy flag. The other thread is the interrupt handler, which is single
87 threaded by the hardware and other software.
88
89 The send packet thread has partial control over the Tx ring and 'dev->tbusy'
90 flag. It sets the tbusy flag whenever it's queuing a Tx packet. If the next
91 queue slot is empty, it clears the tbusy flag when finished otherwise it sets
92 the 'tp->tx_full' flag.
93
94 The interrupt handler has exclusive control over the Rx ring and records stats
95 from the Tx ring. (The Tx-done interrupt can't be selectively turned off, so
96 we can't avoid the interrupt overhead by having the Tx routine reap the Tx
97 stats.) After reaping the stats, it marks the queue entry as empty by setting
98 the 'base' to zero. Iff the 'tp->tx_full' flag is set, it clears both the
99 tx_full and tbusy flags.
100
101 Notes
102 =====
103
104 Thanks to Duke Kamstra of SMC for long ago providing an EtherPower board.
105 Greg LaPolla at Linksys provided PNIC and other Linksys boards.
106 Znyx provided a four-port card for testing.
107
108 References
109 ==========
110
111 http://cesdis.gsfc.nasa.gov/linux/misc/NWay.html
112 http://www.digital.com (search for current 21*4* datasheets and "21X4 SROM")
113 http://www.national.com/pf/DP/DP83840A.html
114 http://www.asix.com.tw/pmac.htm
115 http://www.admtek.com.tw/
116
117 Errata
118 ======
119
120 The old DEC databooks were light on details.
121 The 21040 databook claims that CSR13, CSR14, and CSR15 should each be the last
122 register of the set CSR12-15 written. Hmmm, now how is that possible?
123
124 The DEC SROM format is very badly designed not precisely defined, leading to
125 part of the media selection junkheap below. Some boards do not have EEPROM
126 media tables and need to be patched up. Worse, other boards use the DEC
127 design kit media table when it isn't correct for their board.
128
129 We cannot use MII interrupts because there is no defined GPIO pin to attach
130 them. The MII transceiver status is polled using an kernel timer.
131
132
133 Source tree tour
134 ================
135 The following is a list of files comprising the Tulip ethernet driver in
136 drivers/net/tulip subdirectory.
137
138 21142.c - 21142-specific h/w interaction
139 eeprom.c - EEPROM reading and parsing
140 interrupt.c - Interrupt handler
141 media.c - Media selection and MII support
142 pnic.c - PNIC-specific h/w interaction
143 timer.c - Main driver timer, and misc h/w timers
144 tulip.h - Private driver header
145 tulip_core.c - Driver core (a.k.a. where "everything else" goes)
146
147
148
149 Version history
150 ===============
151 0.9.11 (November 3, 2000):
152 * Eliminate extra bus accesses when sharing interrupts (prumpf)
153 * Barrier following ownership descriptor bit flip (prumpf)
154 * Endianness fixes for >14 addresses in setup frames (prumpf)
155 * Report link beat to kernel/userspace via netif_carrier_*. (kuznet)
156 * Better spinlocking in set_rx_mode.
157 * Fix I/O resource request failure error messages (DaveM catch)
158 * Handle DMA allocation failure.
159
160 0.9.10 (September 6, 2000):
161 * Simple interrupt mitigation (via jamal)
162 * More PCI ids
163
164 0.9.9 (August 11, 2000):
165 * More PCI ids
166
167 0.9.8 (July 13, 2000):
168 * Correct signed/unsigned comparison for dummy frame index
169 * Remove outdated references to struct enet_statistics
170
171 0.9.7 (June 17, 2000):
172 * Timer cleanups (Andrew Morton)
173 * Alpha compile fix (somebody?)
174
175 0.9.6 (May 31, 2000):
176 * Revert 21143-related support flag patch
177 * Add HPPA/media-table debugging printk
178
179 0.9.5 (May 30, 2000):
180 * HPPA support (willy@puffingroup)
181 * CSR6 bits and tulip.h cleanup (Chris Smith)
182 * Improve debugging messages a bit
183 * Add delay after CSR13 write in t21142_start_nway
184 * Remove unused ETHER_STATS code
185 * Convert 'extern inline' to 'static inline' in tulip.h (Chris Smith)
186 * Update DS21143 support flags in tulip_chip_info[]
187 * Use spin_lock_irq, not _irqsave/restore, in tulip_start_xmit()
188 * Add locking to set_rx_mode()
189 * Fix race with chip setting DescOwned bit (Hal Murray)
190 * Request 100% of PIO and MMIO resource space assigned to card
191 * Remove error message from pci_enable_device failure
192
193 0.9.4.3 (April 14, 2000):
194 * mod_timer fix (Hal Murray)
195 * PNIC2 resuscitation (Chris Smith)
196
197 0.9.4.2 (March 21, 2000):
198 * Fix 21041 CSR7, CSR13/14/15 handling
199 * Merge some PCI ids from tulip 0.91x
200 * Merge some HAS_xxx flags and flag settings from tulip 0.91x
201 * asm/io.h fix (submitted by many) and cleanup
202 * s/HAS_NWAY143/HAS_NWAY/
203 * Cleanup 21041 mode reporting
204 * Small code cleanups
205
206 0.9.4.1 (March 18, 2000):
207 * Finish PCI DMA conversion (davem)
208 * Do not netif_start_queue() at end of tulip_tx_timeout() (kuznet)
209 * PCI DMA fix (kuznet)
210 * eeprom.c code cleanup
211 * Remove Xircom Tulip crud
212
213
214 [EOF]
215
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