path: root/Documentation/DocBook/z8530book.tmpl
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authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/DocBook/z8530book.tmpl
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+ "" []>
+<book id="Z85230Guide">
+ <bookinfo>
+ <title>Z8530 Programming Guide</title>
+ <authorgroup>
+ <author>
+ <firstname>Alan</firstname>
+ <surname>Cox</surname>
+ <affiliation>
+ <address>
+ <email></email>
+ </address>
+ </affiliation>
+ </author>
+ </authorgroup>
+ <copyright>
+ <year>2000</year>
+ <holder>Alan Cox</holder>
+ </copyright>
+ <legalnotice>
+ <para>
+ This documentation is free software; you can redistribute
+ it and/or modify it under the terms of the GNU General Public
+ License as published by the Free Software Foundation; either
+ version 2 of the License, or (at your option) any later
+ version.
+ </para>
+ <para>
+ This program is distributed in the hope that it will be
+ useful, but WITHOUT ANY WARRANTY; without even the implied
+ See the GNU General Public License for more details.
+ </para>
+ <para>
+ You should have received a copy of the GNU General Public
+ License along with this program; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ MA 02111-1307 USA
+ </para>
+ <para>
+ For more details see the file COPYING in the source
+ distribution of Linux.
+ </para>
+ </legalnotice>
+ </bookinfo>
+ <chapter id="intro">
+ <title>Introduction</title>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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
+ </para>
+ <para>
+ The support code handles most common card configurations and
+ supports running both Cisco HDLC and Synchronous PPP. With extra
+ glue the frame relay and X.25 protocols can also be used with this
+ driver.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Driver Modes</title>
+ <para>
+ 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).
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Using the Z85230 driver</title>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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 <function>z8530_interrupt</function>. 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.
+ </para>
+ <para>
+ 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 &amp;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
+ 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.
+ </para>
+ <para>
+ 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
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ Having initialised the device you can then call
+ <function>z8530_init</function>. 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.
+ </para>
+ <para>
+ Once you have called z8530_init you can also make use of the utility
+ function <function>z8530_describe</function>. This provides a
+ consistent reporting format for the Z8530 devices, and allows all
+ the drivers to provide consistent reporting.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Attaching Network Interfaces</title>
+ <para>
+ 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 SyncPPP and Cisco 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.
+ </para>
+ <para>
+ The network device used for each channel should be pointed to by
+ the netdevice field of each channel. The dev-&gt; priv field of the
+ network device points to your private data - you will need to be
+ able to find your ppp device from this. In addition to use the
+ sync ppp layer the private data must start with a void * pointer
+ to the syncppp structures.
+ </para>
+ <para>
+ The way most drivers approach this particular problem is to
+ create a structure holding the Z8530 device definition and
+ put that and the syncppp pointer into the private field of
+ the network device. The network device fields of the channels
+ then point back to the network devices. The ppp_device can also
+ be put in the private structure conveniently.
+ </para>
+ <para>
+ If you wish to use the synchronous ppp then you need to attach
+ the syncppp layer to the network device. You should do this before
+ you register the network device. The
+ <function>sppp_attach</function> requires that the first void *
+ pointer in your private data is pointing to an empty struct
+ ppp_device. The function fills in the initial data for the
+ ppp/hdlc layer.
+ </para>
+ <para>
+ 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.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Configuring And Activating The Port</title>
+ <para>
+ 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.
+ </para>
+ <para>
+ <function>z8530_channel_load</function> 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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 <function>z8530_null_rx</function>
+ to discard the data.
+ </para>
+ <para>
+ To active PIO mode sending and receiving the <function>
+ z8530_sync_open</function> 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 <function>z8530_sync_close</function>
+ function shuts down a PIO channel. This must be done before the
+ channel is opened again and before the driver shuts down
+ and unloads.
+ </para>
+ <para>
+ 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 <function>z8530_sync_dma_open</function>
+ function. On failure a non zero error value is returned.
+ Once this mode is activated it can be shut down by calling the
+ <function>z8530_sync_dma_close</function>. You must call the close
+ function matching the open mode you used.
+ </para>
+ <para>
+ 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 <function>z8530_sync_txdma_open
+ </function>. This returns a non zero error code on failure. The
+ <function>z8530_sync_txdma_close</function> function closes down
+ the Z8530 interface from this mode.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Network Layer Functions</title>
+ <para>
+ 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.
+ </para>
+ <para>
+ The function <function>z8530_queue_xmit</function> 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 syncppp 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.
+ </para>
+ <para>
+ The function <function>z8530_get_stats</function> 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.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Porting The Z8530 Driver</title>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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
+ <function>z8530_read_port</function> and <function>z8530_write_port
+ </function> is intended to be all that is required to port this
+ driver layer.
+ </para>
+ </chapter>
+ <chapter id="bugs">
+ <title>Known Bugs And Assumptions</title>
+ <para>
+ <variablelist>
+ <varlistentry><term>Interrupt Locking</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem></varlistentry>
+ <varlistentry><term>Occasional Failures</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem></varlistentry>
+ </variablelist>
+ </para>
+ </chapter>
+ <chapter id="pubfunctions">
+ <title>Public Functions Provided</title>
+ </chapter>
+ <chapter id="intfunctions">
+ <title>Internal Functions</title>
+ </chapter>