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docs: networking: move z8530 to the hw driver section

Pārlūkot izejas kodu 
Move z8530 docs to hamradio and wan subdirectories.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Šī revīzija ir iekļauta:
Jakub Kicinski
2020-06-26 10:27:25 -07:00
revīziju iesūtīja David S. Miller
vecāks 132db93572
revīzija 1447495025
9 mainīti faili ar 45 papildinājumiem un 7 dzēšanām
Lejupielādēt ielāpa failu Lejupielādēt izmaiņu failu Izvērst visus failus Savērst visus failus

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.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
Amateur Radio Device Drivers
============================
Contents:
.. toctree::
:maxdepth: 2
z8530drv
.. only:: subproject and html
Indices
=======
* :ref:`genindex`

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.. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>
=========================================================
SCC.C - Linux driver for Z8530 based HDLC cards for AX.25
=========================================================
This is a subset of the documentation. To use this driver you MUST have the
full package from:
Internet:
1. ftp://ftp.ccac.rwth-aachen.de/pub/jr/z8530drv-utils_3.0-3.tar.gz
2. ftp://ftp.pspt.fi/pub/ham/linux/ax25/z8530drv-utils_3.0-3.tar.gz
Please note that the information in this document may be hopelessly outdated.
A new version of the documentation, along with links to other important
Linux Kernel AX.25 documentation and programs, is available on
http://yaina.de/jreuter
Copyright |copy| 1993,2000 by Joerg Reuter DL1BKE <jreuter@yaina.de>
portions Copyright |copy| 1993 Guido ten Dolle PE1NNZ
for the complete copyright notice see >> Copying.Z8530DRV <<
1. Initialization of the driver
===============================
To use the driver, 3 steps must be performed:
1. if compiled as module: loading the module
2. Setup of hardware, MODEM and KISS parameters with sccinit
3. Attach each channel to the Linux kernel AX.25 with "ifconfig"
Unlike the versions below 2.4 this driver is a real network device
driver. If you want to run xNOS instead of our fine kernel AX.25
use a 2.x version (available from above sites) or read the
AX.25-HOWTO on how to emulate a KISS TNC on network device drivers.
1.1 Loading the module
======================
(If you're going to compile the driver as a part of the kernel image,
skip this chapter and continue with 1.2)
Before you can use a module, you'll have to load it with::
insmod scc.o
please read 'man insmod' that comes with module-init-tools.
You should include the insmod in one of the /etc/rc.d/rc.* files,
and don't forget to insert a call of sccinit after that. It
will read your /etc/z8530drv.conf.
1.2. /etc/z8530drv.conf
=======================
To setup all parameters you must run /sbin/sccinit from one
of your rc.*-files. This has to be done BEFORE you can
"ifconfig" an interface. Sccinit reads the file /etc/z8530drv.conf
and sets the hardware, MODEM and KISS parameters. A sample file is
delivered with this package. Change it to your needs.
The file itself consists of two main sections.
1.2.1 configuration of hardware parameters
==========================================
The hardware setup section defines the following parameters for each
Z8530::
chip 1
data_a 0x300 # data port A
ctrl_a 0x304 # control port A
data_b 0x301 # data port B
ctrl_b 0x305 # control port B
irq 5 # IRQ No. 5
pclock 4915200 # clock
board BAYCOM # hardware type
escc no # enhanced SCC chip? (8580/85180/85280)
vector 0 # latch for interrupt vector
special no # address of special function register
option 0 # option to set via sfr
chip
- this is just a delimiter to make sccinit a bit simpler to
program. A parameter has no effect.
data_a
- the address of the data port A of this Z8530 (needed)
ctrl_a
- the address of the control port A (needed)
data_b
- the address of the data port B (needed)
ctrl_b
- the address of the control port B (needed)
irq
- the used IRQ for this chip. Different chips can use different
IRQs or the same. If they share an interrupt, it needs to be
specified within one chip-definition only.
pclock - the clock at the PCLK pin of the Z8530 (option, 4915200 is
default), measured in Hertz
board
- the "type" of the board:
======================= ========
SCC type value
======================= ========
PA0HZP SCC card PA0HZP
EAGLE card EAGLE
PC100 card PC100
PRIMUS-PC (DG9BL) card PRIMUS
BayCom (U)SCC card BAYCOM
======================= ========
escc
- if you want support for ESCC chips (8580, 85180, 85280), set
this to "yes" (option, defaults to "no")
vector
- address of the vector latch (aka "intack port") for PA0HZP
cards. There can be only one vector latch for all chips!
(option, defaults to 0)
special
- address of the special function register on several cards.
(option, defaults to 0)
option - The value you write into that register (option, default is 0)
You can specify up to four chips (8 channels). If this is not enough,
just change::
#define MAXSCC 4
to a higher value.
Example for the BAYCOM USCC:
----------------------------
::
chip 1
data_a 0x300 # data port A
ctrl_a 0x304 # control port A
data_b 0x301 # data port B
ctrl_b 0x305 # control port B
irq 5 # IRQ No. 5 (#)
board BAYCOM # hardware type (*)
#
# SCC chip 2
#
chip 2
data_a 0x302
ctrl_a 0x306
data_b 0x303
ctrl_b 0x307
board BAYCOM
An example for a PA0HZP card:
-----------------------------
::
chip 1
data_a 0x153
data_b 0x151
ctrl_a 0x152
ctrl_b 0x150
irq 9
pclock 4915200
board PA0HZP
vector 0x168
escc no
#
#
#
chip 2
data_a 0x157
data_b 0x155
ctrl_a 0x156
ctrl_b 0x154
irq 9
pclock 4915200
board PA0HZP
vector 0x168
escc no
A DRSI would should probably work with this:
--------------------------------------------
(actually: two DRSI cards...)
::
chip 1
data_a 0x303
data_b 0x301
ctrl_a 0x302
ctrl_b 0x300
irq 7
pclock 4915200
board DRSI
escc no
#
#
#
chip 2
data_a 0x313
data_b 0x311
ctrl_a 0x312
ctrl_b 0x310
irq 7
pclock 4915200
board DRSI
escc no
Note that you cannot use the on-board baudrate generator off DRSI
cards. Use "mode dpll" for clock source (see below).
This is based on information provided by Mike Bilow (and verified
by Paul Helay)
The utility "gencfg"
--------------------
If you only know the parameters for the PE1CHL driver for DOS,
run gencfg. It will generate the correct port addresses (I hope).
Its parameters are exactly the same as the ones you use with
the "attach scc" command in net, except that the string "init" must
not appear. Example::
gencfg 2 0x150 4 2 0 1 0x168 9 4915200
will print a skeleton z8530drv.conf for the OptoSCC to stdout.
::
gencfg 2 0x300 2 4 5 -4 0 7 4915200 0x10
does the same for the BAYCOM USCC card. In my opinion it is much easier
to edit scc_config.h...
1.2.2 channel configuration
===========================
The channel definition is divided into three sub sections for each
channel:
An example for scc0::
# DEVICE
device scc0 # the device for the following params
# MODEM / BUFFERS
speed 1200 # the default baudrate
clock dpll # clock source:
# dpll = normal half duplex operation
# external = MODEM provides own Rx/Tx clock
# divider = use full duplex divider if
# installed (1)
mode nrzi # HDLC encoding mode
# nrzi = 1k2 MODEM, G3RUH 9k6 MODEM
# nrz = DF9IC 9k6 MODEM
#
bufsize 384 # size of buffers. Note that this must include
# the AX.25 header, not only the data field!
# (optional, defaults to 384)
# KISS (Layer 1)
txdelay 36 # (see chapter 1.4)
persist 64
slot 8
tail 8
fulldup 0
wait 12
min 3
maxkey 7
idle 3
maxdef 120
group 0
txoff off
softdcd on
slip off
The order WITHIN these sections is unimportant. The order OF these
sections IS important. The MODEM parameters are set with the first
recognized KISS parameter...
Please note that you can initialize the board only once after boot
(or insmod). You can change all parameters but "mode" and "clock"
later with the Sccparam program or through KISS. Just to avoid
security holes...
(1) this divider is usually mounted on the SCC-PBC (PA0HZP) or not
present at all (BayCom). It feeds back the output of the DPLL
(digital pll) as transmit clock. Using this mode without a divider
installed will normally result in keying the transceiver until
maxkey expires --- of course without sending anything (useful).
2. Attachment of a channel by your AX.25 software
=================================================
2.1 Kernel AX.25
================
To set up an AX.25 device you can simply type::
ifconfig scc0 44.128.1.1 hw ax25 dl0tha-7
This will create a network interface with the IP number 44.128.20.107
and the callsign "dl0tha". If you do not have any IP number (yet) you
can use any of the 44.128.0.0 network. Note that you do not need
axattach. The purpose of axattach (like slattach) is to create a KISS
network device linked to a TTY. Please read the documentation of the
ax25-utils and the AX.25-HOWTO to learn how to set the parameters of
the kernel AX.25.
2.2 NOS, NET and TFKISS
=======================
Since the TTY driver (aka KISS TNC emulation) is gone you need
to emulate the old behaviour. The cost of using these programs is
that you probably need to compile the kernel AX.25, regardless of whether
you actually use it or not. First setup your /etc/ax25/axports,
for example::
9k6 dl0tha-9 9600 255 4 9600 baud port (scc3)
axlink dl0tha-15 38400 255 4 Link to NOS
Now "ifconfig" the scc device::
ifconfig scc3 44.128.1.1 hw ax25 dl0tha-9
You can now axattach a pseudo-TTY::
axattach /dev/ptys0 axlink
and start your NOS and attach /dev/ptys0 there. The problem is that
NOS is reachable only via digipeating through the kernel AX.25
(disastrous on a DAMA controlled channel). To solve this problem,
configure "rxecho" to echo the incoming frames from "9k6" to "axlink"
and outgoing frames from "axlink" to "9k6" and start::
rxecho
Or simply use "kissbridge" coming with z8530drv-utils::
ifconfig scc3 hw ax25 dl0tha-9
kissbridge scc3 /dev/ptys0
3. Adjustment and Display of parameters
=======================================
3.1 Displaying SCC Parameters:
==============================
Once a SCC channel has been attached, the parameter settings and
some statistic information can be shown using the param program::
dl1bke-u:~$ sccstat scc0
Parameters:
speed : 1200 baud
txdelay : 36
persist : 255
slottime : 0
txtail : 8
fulldup : 1
waittime : 12
mintime : 3 sec
maxkeyup : 7 sec
idletime : 3 sec
maxdefer : 120 sec
group : 0x00
txoff : off
softdcd : on
SLIP : off
Status:
HDLC Z8530 Interrupts Buffers
-----------------------------------------------------------------------
Sent : 273 RxOver : 0 RxInts : 125074 Size : 384
Received : 1095 TxUnder: 0 TxInts : 4684 NoSpace : 0
RxErrors : 1591 ExInts : 11776
TxErrors : 0 SpInts : 1503
Tx State : idle
The status info shown is:
============== ==============================================================
Sent number of frames transmitted
Received number of frames received
RxErrors number of receive errors (CRC, ABORT)
TxErrors number of discarded Tx frames (due to various reasons)
Tx State status of the Tx interrupt handler: idle/busy/active/tail (2)
RxOver number of receiver overruns
TxUnder number of transmitter underruns
RxInts number of receiver interrupts
TxInts number of transmitter interrupts
EpInts number of receiver special condition interrupts
SpInts number of external/status interrupts
Size maximum size of an AX.25 frame (*with* AX.25 headers!)
NoSpace number of times a buffer could not get allocated
============== ==============================================================
An overrun is abnormal. If lots of these occur, the product of
baudrate and number of interfaces is too high for the processing
power of your computer. NoSpace errors are unlikely to be caused by the
driver or the kernel AX.25.
3.2 Setting Parameters
======================
The setting of parameters of the emulated KISS TNC is done in the
same way in the SCC driver. You can change parameters by using
the kissparms program from the ax25-utils package or use the program
"sccparam"::
sccparam <device> <paramname> <decimal-|hexadecimal value>
You can change the following parameters:
=========== =====
param value
=========== =====
speed 1200
txdelay 36
persist 255
slottime 0
txtail 8
fulldup 1
waittime 12
mintime 3
maxkeyup 7
idletime 3
maxdefer 120
group 0x00
txoff off
softdcd on
SLIP off
=========== =====
The parameters have the following meaning:
speed:
The baudrate on this channel in bits/sec
Example: sccparam /dev/scc3 speed 9600
txdelay:
The delay (in units of 10 ms) after keying of the
transmitter, until the first byte is sent. This is usually
called "TXDELAY" in a TNC. When 0 is specified, the driver
will just wait until the CTS signal is asserted. This
assumes the presence of a timer or other circuitry in the
MODEM and/or transmitter, that asserts CTS when the
transmitter is ready for data.
A normal value of this parameter is 30-36.
Example: sccparam /dev/scc0 txd 20
persist:
This is the probability that the transmitter will be keyed
when the channel is found to be free. It is a value from 0
to 255, and the probability is (value+1)/256. The value
should be somewhere near 50-60, and should be lowered when
the channel is used more heavily.
Example: sccparam /dev/scc2 persist 20
slottime:
This is the time between samples of the channel. It is
expressed in units of 10 ms. About 200-300 ms (value 20-30)
seems to be a good value.
Example: sccparam /dev/scc0 slot 20
tail:
The time the transmitter will remain keyed after the last
byte of a packet has been transferred to the SCC. This is
necessary because the CRC and a flag still have to leave the
SCC before the transmitter is keyed down. The value depends
on the baudrate selected. A few character times should be
sufficient, e.g. 40ms at 1200 baud. (value 4)
The value of this parameter is in 10 ms units.
Example: sccparam /dev/scc2 4
full:
The full-duplex mode switch. This can be one of the following
values:
0: The interface will operate in CSMA mode (the normal
half-duplex packet radio operation)
1: Fullduplex mode, i.e. the transmitter will be keyed at
any time, without checking the received carrier. It
will be unkeyed when there are no packets to be sent.
2: Like 1, but the transmitter will remain keyed, also
when there are no packets to be sent. Flags will be
sent in that case, until a timeout (parameter 10)
occurs.
Example: sccparam /dev/scc0 fulldup off
wait:
The initial waittime before any transmit attempt, after the
frame has been queue for transmit. This is the length of
the first slot in CSMA mode. In full duplex modes it is
set to 0 for maximum performance.
The value of this parameter is in 10 ms units.
Example: sccparam /dev/scc1 wait 4
maxkey:
The maximal time the transmitter will be keyed to send
packets, in seconds. This can be useful on busy CSMA
channels, to avoid "getting a bad reputation" when you are
generating a lot of traffic. After the specified time has
elapsed, no new frame will be started. Instead, the trans-
mitter will be switched off for a specified time (parameter
min), and then the selected algorithm for keyup will be
started again.
The value 0 as well as "off" will disable this feature,
and allow infinite transmission time.
Example: sccparam /dev/scc0 maxk 20
min:
This is the time the transmitter will be switched off when
the maximum transmission time is exceeded.
Example: sccparam /dev/scc3 min 10
idle:
This parameter specifies the maximum idle time in full duplex
2 mode, in seconds. When no frames have been sent for this
time, the transmitter will be keyed down. A value of 0 is
has same result as the fullduplex mode 1. This parameter
can be disabled.
Example: sccparam /dev/scc2 idle off # transmit forever
maxdefer
This is the maximum time (in seconds) to wait for a free channel
to send. When this timer expires the transmitter will be keyed
IMMEDIATELY. If you love to get trouble with other users you
should set this to a very low value ;-)
Example: sccparam /dev/scc0 maxdefer 240 # 2 minutes
txoff:
When this parameter has the value 0, the transmission of packets
is enable. Otherwise it is disabled.
Example: sccparam /dev/scc2 txoff on
group:
It is possible to build special radio equipment to use more than
one frequency on the same band, e.g. using several receivers and
only one transmitter that can be switched between frequencies.
Also, you can connect several radios that are active on the same
band. In these cases, it is not possible, or not a good idea, to
transmit on more than one frequency. The SCC driver provides a
method to lock transmitters on different interfaces, using the
"param <interface> group <x>" command. This will only work when
you are using CSMA mode (parameter full = 0).
The number <x> must be 0 if you want no group restrictions, and
can be computed as follows to create restricted groups:
<x> is the sum of some OCTAL numbers:
=== =======================================================
200 This transmitter will only be keyed when all other
transmitters in the group are off.
100 This transmitter will only be keyed when the carrier
detect of all other interfaces in the group is off.
0xx A byte that can be used to define different groups.
Interfaces are in the same group, when the logical AND
between their xx values is nonzero.
=== =======================================================
Examples:
When 2 interfaces use group 201, their transmitters will never be
keyed at the same time.
When 2 interfaces use group 101, the transmitters will only key
when both channels are clear at the same time. When group 301,
the transmitters will not be keyed at the same time.
Don't forget to convert the octal numbers into decimal before
you set the parameter.
Example: (to be written)
softdcd:
use a software dcd instead of the real one... Useful for a very
slow squelch.
Example: sccparam /dev/scc0 soft on
4. Problems
===========
If you have tx-problems with your BayCom USCC card please check
the manufacturer of the 8530. SGS chips have a slightly
different timing. Try Zilog... A solution is to write to register 8
instead to the data port, but this won't work with the ESCC chips.
*SIGH!*
A very common problem is that the PTT locks until the maxkeyup timer
expires, although interrupts and clock source are correct. In most
cases compiling the driver with CONFIG_SCC_DELAY (set with
make config) solves the problems. For more hints read the (pseudo) FAQ
and the documentation coming with z8530drv-utils.
I got reports that the driver has problems on some 386-based systems.
(i.e. Amstrad) Those systems have a bogus AT bus timing which will
lead to delayed answers on interrupts. You can recognize these
problems by looking at the output of Sccstat for the suspected
port. If it shows under- and overruns you own such a system.
Delayed processing of received data: This depends on
- the kernel version
- kernel profiling compiled or not
- a high interrupt load
- a high load of the machine --- running X, Xmorph, XV and Povray,
while compiling the kernel... hmm ... even with 32 MB RAM ... ;-)
Or running a named for the whole .ampr.org domain on an 8 MB
box...
- using information from rxecho or kissbridge.
Kernel panics: please read /linux/README and find out if it
really occurred within the scc driver.
If you cannot solve a problem, send me
- a description of the problem,
- information on your hardware (computer system, scc board, modem)
- your kernel version
- the output of cat /proc/net/z8530
4. Thor RLC100
==============
Mysteriously this board seems not to work with the driver. Anyone
got it up-and-running?
Many thanks to Linus Torvalds and Alan Cox for including the driver
in the Linux standard distribution and their support.
::
Joerg Reuter ampr-net: dl1bke@db0pra.ampr.org
AX-25 : DL1BKE @ DB0ABH.#BAY.DEU.EU
Internet: jreuter@yaina.de
WWW : http://yaina.de/jreuter

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cable/index
cellular/index
ethernet/index
hamradio/index
wan/index
wifi/index
.. only:: subproject and html

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.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
Classic WAN Device Drivers
==========================
Contents:
.. toctree::
:maxdepth: 2
z8530book
.. only:: subproject and html
Indices
=======
* :ref:`genindex`

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=======================
Z8530 Programming Guide
=======================
:Author: Alan Cox
Introduction
============
The Z85x30 family synchronous/asynchronous controller chips are used on
a large number of cheap network interface cards. The kernel provides a
core interface layer that is designed to make it easy to provide WAN
services using this chip.
The current driver only support synchronous operation. Merging the
asynchronous driver support into this code to allow any Z85x30 device to
be used as both a tty interface and as a synchronous controller is a
project for Linux post the 2.4 release
Driver Modes
============
The Z85230 driver layer can drive Z8530, Z85C30 and Z85230 devices in
three different modes. Each mode can be applied to an individual channel
on the chip (each chip has two channels).
The PIO synchronous mode supports the most common Z8530 wiring. Here the
chip is interface to the I/O and interrupt facilities of the host
machine but not to the DMA subsystem. When running PIO the Z8530 has
extremely tight timing requirements. Doing high speeds, even with a
Z85230 will be tricky. Typically you should expect to achieve at best
9600 baud with a Z8C530 and 64Kbits with a Z85230.
The DMA mode supports the chip when it is configured to use dual DMA
channels on an ISA bus. The better cards tend to support this mode of
operation for a single channel. With DMA running the Z85230 tops out
when it starts to hit ISA DMA constraints at about 512Kbits. It is worth
noting here that many PC machines hang or crash when the chip is driven
fast enough to hold the ISA bus solid.
Transmit DMA mode uses a single DMA channel. The DMA channel is used for
transmission as the transmit FIFO is smaller than the receive FIFO. it
gives better performance than pure PIO mode but is nowhere near as ideal
as pure DMA mode.
Using the Z85230 driver
=======================
The Z85230 driver provides the back end interface to your board. To
configure a Z8530 interface you need to detect the board and to identify
its ports and interrupt resources. It is also your problem to verify the
resources are available.
Having identified the chip you need to fill in a struct z8530_dev,
which describes each chip. This object must exist until you finally
shutdown the board. Firstly zero the active field. This ensures nothing
goes off without you intending it. The irq field should be set to the
interrupt number of the chip. (Each chip has a single interrupt source
rather than each channel). You are responsible for allocating the
interrupt line. The interrupt handler should be set to
:c:func:`z8530_interrupt()`. The device id should be set to the
z8530_dev structure pointer. Whether the interrupt can be shared or not
is board dependent, and up to you to initialise.
The structure holds two channel structures. Initialise chanA.ctrlio and
chanA.dataio with the address of the control and data ports. You can or
this with Z8530_PORT_SLEEP to indicate your interface needs the 5uS
delay for chip settling done in software. The PORT_SLEEP option is
architecture specific. Other flags may become available on future
platforms, eg for MMIO. Initialise the chanA.irqs to &z8530_nop to
start the chip up as disabled and discarding interrupt events. This
ensures that stray interrupts will be mopped up and not hang the bus.
Set chanA.dev to point to the device structure itself. The private and
name field you may use as you wish. The private field is unused by the
Z85230 layer. The name is used for error reporting and it may thus make
sense to make it match the network name.
Repeat the same operation with the B channel if your chip has both
channels wired to something useful. This isn't always the case. If it is
not wired then the I/O values do not matter, but you must initialise
chanB.dev.
If your board has DMA facilities then initialise the txdma and rxdma
fields for the relevant channels. You must also allocate the ISA DMA
channels and do any necessary board level initialisation to configure
them. The low level driver will do the Z8530 and DMA controller
programming but not board specific magic.
Having initialised the device you can then call
:c:func:`z8530_init()`. This will probe the chip and reset it into
a known state. An identification sequence is then run to identify the
chip type. If the checks fail to pass the function returns a non zero
error code. Typically this indicates that the port given is not valid.
After this call the type field of the z8530_dev structure is
initialised to either Z8530, Z85C30 or Z85230 according to the chip
found.
Once you have called z8530_init you can also make use of the utility
function :c:func:`z8530_describe()`. This provides a consistent
reporting format for the Z8530 devices, and allows all the drivers to
provide consistent reporting.
Attaching Network Interfaces
============================
If you wish to use the network interface facilities of the driver, then
you need to attach a network device to each channel that is present and
in use. In addition to use the generic HDLC you need to follow some
additional plumbing rules. They may seem complex but a look at the
example hostess_sv11 driver should reassure you.
The network device used for each channel should be pointed to by the
netdevice field of each channel. The hdlc-> priv field of the network
device points to your private data - you will need to be able to find
your private data from this.
The way most drivers approach this particular problem is to create a
structure holding the Z8530 device definition and put that into the
private field of the network device. The network device fields of the
channels then point back to the network devices.
If you wish to use the generic HDLC then you need to register the HDLC
device.
Before you register your network device you will also need to provide
suitable handlers for most of the network device callbacks. See the
network device documentation for more details on this.
Configuring And Activating The Port
===================================
The Z85230 driver provides helper functions and tables to load the port
registers on the Z8530 chips. When programming the register settings for
a channel be aware that the documentation recommends initialisation
orders. Strange things happen when these are not followed.
:c:func:`z8530_channel_load()` takes an array of pairs of
initialisation values in an array of u8 type. The first value is the
Z8530 register number. Add 16 to indicate the alternate register bank on
the later chips. The array is terminated by a 255.
The driver provides a pair of public tables. The z8530_hdlc_kilostream
table is for the UK 'Kilostream' service and also happens to cover most
other end host configurations. The z8530_hdlc_kilostream_85230 table
is the same configuration using the enhancements of the 85230 chip. The
configuration loaded is standard NRZ encoded synchronous data with HDLC
bitstuffing. All of the timing is taken from the other end of the link.
When writing your own tables be aware that the driver internally tracks
register values. It may need to reload values. You should therefore be
sure to set registers 1-7, 9-11, 14 and 15 in all configurations. Where
the register settings depend on DMA selection the driver will update the
bits itself when you open or close. Loading a new table with the
interface open is not recommended.
There are three standard configurations supported by the core code. In
PIO mode the interface is programmed up to use interrupt driven PIO.
This places high demands on the host processor to avoid latency. The
driver is written to take account of latency issues but it cannot avoid
latencies caused by other drivers, notably IDE in PIO mode. Because the
drivers allocate buffers you must also prevent MTU changes while the
port is open.
Once the port is open it will call the rx_function of each channel
whenever a completed packet arrived. This is invoked from interrupt
context and passes you the channel and a network buffer (struct
sk_buff) holding the data. The data includes the CRC bytes so most
users will want to trim the last two bytes before processing the data.
This function is very timing critical. When you wish to simply discard
data the support code provides the function
:c:func:`z8530_null_rx()` to discard the data.
To active PIO mode sending and receiving the ``z8530_sync_open`` is called.
This expects to be passed the network device and the channel. Typically
this is called from your network device open callback. On a failure a
non zero error status is returned.
The :c:func:`z8530_sync_close()` function shuts down a PIO
channel. This must be done before the channel is opened again and before
the driver shuts down and unloads.
The ideal mode of operation is dual channel DMA mode. Here the kernel
driver will configure the board for DMA in both directions. The driver
also handles ISA DMA issues such as controller programming and the
memory range limit for you. This mode is activated by calling the
:c:func:`z8530_sync_dma_open()` function. On failure a non zero
error value is returned. Once this mode is activated it can be shut down
by calling the :c:func:`z8530_sync_dma_close()`. You must call
the close function matching the open mode you used.
The final supported mode uses a single DMA channel to drive the transmit
side. As the Z85C30 has a larger FIFO on the receive channel this tends
to increase the maximum speed a little. This is activated by calling the
``z8530_sync_txdma_open``. This returns a non zero error code on failure. The
:c:func:`z8530_sync_txdma_close()` function closes down the Z8530
interface from this mode.
Network Layer Functions
=======================
The Z8530 layer provides functions to queue packets for transmission.
The driver internally buffers the frame currently being transmitted and
one further frame (in order to keep back to back transmission running).
Any further buffering is up to the caller.
The function :c:func:`z8530_queue_xmit()` takes a network buffer
in sk_buff format and queues it for transmission. The caller must
provide the entire packet with the exception of the bitstuffing and CRC.
This is normally done by the caller via the generic HDLC interface
layer. It returns 0 if the buffer has been queued and non zero values
for queue full. If the function accepts the buffer it becomes property
of the Z8530 layer and the caller should not free it.
The function :c:func:`z8530_get_stats()` returns a pointer to an
internally maintained per interface statistics block. This provides most
of the interface code needed to implement the network layer get_stats
callback.
Porting The Z8530 Driver
========================
The Z8530 driver is written to be portable. In DMA mode it makes
assumptions about the use of ISA DMA. These are probably warranted in
most cases as the Z85230 in particular was designed to glue to PC type
machines. The PIO mode makes no real assumptions.
Should you need to retarget the Z8530 driver to another architecture the
only code that should need changing are the port I/O functions. At the
moment these assume PC I/O port accesses. This may not be appropriate
for all platforms. Replacing :c:func:`z8530_read_port()` and
``z8530_write_port`` is intended to be all that is required to port
this driver layer.
Known Bugs And Assumptions
==========================
Interrupt Locking
The locking in the driver is done via the global cli/sti lock. This
makes for relatively poor SMP performance. Switching this to use a
per device spin lock would probably materially improve performance.
Occasional Failures
We have reports of occasional failures when run for very long
periods of time and the driver starts to receive junk frames. At the
moment the cause of this is not clear.
Public Functions Provided
=========================
.. kernel-doc:: drivers/net/wan/z85230.c
:export:
Internal Functions
==================
.. kernel-doc:: drivers/net/wan/z85230.c
:internal: